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Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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KEEP IT SIMPLE SCIENCE PhotoMaster Format
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keep it simple science
Maintaining a Balance
Senior Science Subject
Topic Bio 9.2
Biology HSC Course Topic 1
NSW Syllabus Content reference
Maintaining a Balance
Topic Outline
4. Excretion & Water Balance
1. Enzymes & Homeostasis
Kidney Structure & Function Water Balance in Insects, Mammals & Plants
Functions & Characteristics of Enzymes Factors which affect enzyme activity Concept of Negative Feedback
2. Temperature Regulation
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Hypothalamus & Temperature Effector Organs Range of Life Temperature Regulation in Ectotherms, Endotherms & Plants
3. Internal Transport Blood & Blood Vessels Substances Transported Transport in Plants
What is this topic about? To keep it as simple as possible, (K.I.S.S. Principle) this topic covers:
1. ENZYMES & HOMEOSTASIS What are enzymes? Functions & characteristics. Factors that affect enzyme activity... temperature, pH & substrate concentration. Negative feedback control systems. What is Homeostasis?
2. TEMPERATURE REGULATION IN LIVING THINGS The hypothalamus & effector organs in mammals. Temperature regulation in endotherms, exotherms & plants.
3. INTERNAL TRANSPORT SYSTEMS Blood & blood vessels. What the blood carries. Gas transport. Transport in plants... xylem & phloem.
4. EXCRETION & WATER BALANCE Importance of water for homeostasis. Kidney & nephron structure & function. Water balance in insects & mammals. Water conservation in plants. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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1. Enzymes & Homeostasis
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Metabolism is Chemistry
The Importance of Shape
Everything that happens inside a living thing is really a matter of cell chemistry... “metabolism”. For example...
Many of the properties of enzymes are related to their precise 3-dimensional shape. The shape of the enzyme fits the “substrate” molecule(s) as closely as a key fits a lock.
• For your body to grow, cells must divide and add more membranes, cytoplasm and organelles. This involves the chemical construction of new DNA molecules, new phospholipids for membranes and so on.
Various Only this one fits
Enzyme molecule
• All these chemical reactions require energy. Energy is delivered by the ATP molecule, itself the product of a series of chemical reactions in the mitochondria... cellular respiration.
Different Substrate Molecules
All of these reactions are “metabolism”: the sum total of all the thousands of chemical reactions going on constantly in all the billions of cells in your body.
This is why enzymes are “substrate-specific”... only one particular enzyme can fit each substrate molecule. Each chemical reaction requires a different enzyme.
Enzymes
Changes in temperature and pH (acidity) can cause the shape of the enzyme to change. If it changes its shape even slightly, it might not fit the substrate properly any more, so the reaction cannot run as quickly and efficiently. This is why enzymes are found to work best at particular “optimum” temperature and pH values.
Every reaction requires a catalyst... a chemical which speeds the reaction up and makes it happen, without being changed in the process. In living cells there is a catalyst for every different reaction. Biological catalysts are called enzymes. Enzymes are protein molecules.
Substrate...
Each has a particular 3-dimensional shape, which fits its “substrate” perfectly. Enzymes are highly “specific”. This means that each enzyme will only catalyse one particular reaction, and no other.
Enzyme shape at optimum pH and temperature
Enzymes only work effectively in a relatively narrow range of temperature and pH (acidity).
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...no longer fits enzyme
From Amino Acids to Enzyme, to Metabolic Control
Amino acid molecules
Protein, with precise 3-D shape...
Polypeptide chain
Polymerisation
Enzyme’s “Active Site” has a shape to fit the substrate(s) exactly
Shape changes slightly at different pH or temp.
...becomes an ENZYME molecule
Twists & folds
Substrate molecules are chemically attracted to the enzyme’s active site
ENZYME
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Substrate molecules brought together and react with each other
ENZYME Page 3
Product released from enzyme
ENZYME can react with more substrate Inspection Copy for Schools only.
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The pH Scale
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The acidity or alkalinity of any solution is measured on a numerical scale known as “pH”.
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increasing acidity
On the pH scale, anything which is neutral (neither acid nor alkaline) has a pH = 7. 3
4
6
5
increasing alkalinity
Neutral 7
8
9
10
11
The inside environment of a cell, and most parts of an organism’s body, is always very close to pH 7... i.e. neutral. An exception is in the stomach where conditions are strongly acidic. (approx. pH 2)
Enzyme Activity Graphs You will have done experimental work to measure the “activity” of an enzyme under different conditions of temperature, pH and the concentration of the substrate chemical. You may have measured the rate of a chemical reaction being catalysed by an enzyme, such as: • the rate of milk clotting by junket tablets. • the rate of digestion of some starch by amylase • the rate of decomposition of hydrogen peroxide by “catalase” enzyme.
A common way to measure the rate of a reaction is to measure the time taken for a reaction to reach completion... the shorter the time taken, the faster the reaction. This why the reciprocal of time taken (1/time) is used as the measure of rate of reaction.
The Effect of Temperature When enzyme activity is measured at different temperatures, the results produce a graph as below.
1/time taken for reaction (rate)
Explanations Experimental Points
As temperature rises the rate increases because the molecules move faster and are more likely to collide and react. All chemical reactions show this response. However, beyond a certain “optimum” temperature, the enzyme’s 3-D shape begins to change. The substrate no longer fits the active site so well, and the reaction slows. If the temperature was lowered again, the enzyme shape, and reaction rate could be restored.
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If the temperature reaches an extreme level, the distortion of the enzyme’s shape may result in total shut-down of the reaction. The enzyme may be permanently distorted out of shape, and its activity cannot be restored. We say the enzyme has been “denatured”.
Temperature
Optimum Temperature Not all enzymes will “peak” at the same temperature, or have exactly the same shape graph. In mammals, most enzymes will peak at around the animal’s normal body temperature, and often work only within a narrow range of temperatures. An enzyme from a plant may show a much broader graph, indicating that it will work, at least partly, at a wider range of temperatures. An enzyme from a thermophilic bacteria from a hot volcanic spring will show a totally different “peak” temperature, indicating that its metabolism will perform most efficiently at temperatures that would kill other organisms. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Reaction Rate
Mammal Enzyme
Plant Enzyme
0
Thermophilic bacteria enzyme
20 40 60 80 o Temperature ( C)
100
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The Effect of pH
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When the temperature is kept constant and the enzyme tested at various pH levels, the results will produce a graph as shown.
The digestive enzyme “pepsin” from the stomach shows an optimum pH about 2 or 3, allowing it to work best in the acidic environment. Intra-cellular enzyme
1/time (rate) Enzyme Activity
The shape of the pH graph is usually symmetrical on either side of the “peak”.
Pepsin. (Stomach enzyme) Enzyme Activity
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The explanation for the shape is as follows: 2
3
4
5
6
pH
7
8
9 10
Generally, all intra-cellular enzymes (i.e. those from within a cell) will show peak activity at about pH = 7, very close to neutrality.
1
2
3
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6
pH
7
8
9 10
11
• at the optimum pH the enzyme’s 3-D shape is ideal for the substrate, so reaction rate is maximum. • at any pH higher or lower than optimum, the enzyme’s shape begins to change. The substrate no longer fits, so activity is less. • at extremes of pH, the enzyme can be denatured and shows no activity at all.
Effect of Substrate Concentration Generally in any chemical reaction occurring in solution the rate of the reaction increases if the concentration of the reacting chemical(s) is increased. The explanation is simply that if the molecules are more concentrated, then it becomes more likely that they will collide and react with each other. When an enzyme is involved, the situation is a little more complicated:
If, at this point, you were to add more enzyme then the reaction rate would once again go up. It would level off again as the enzyme molecules were once again swamped and saturated with the substrate.
Initially the rate of the reaction increases as the substrate concentration goes up, just as it does with any reaction. Soon though, the graph begins to flatten out and level off because the enzyme molecules are “saturated” with substrate and cannot work any faster. Reaction Rate
Reaction Rate
Levels out
Extra enzyme added
Initial Increase in Rate
INSPECTION COPY for schools only Substrate Concentration
Substrate Concentration
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Homeostasis
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Metabolism is largely a matter of chemical reactions, and each reaction is catalysed by an enzyme. Enzymes are very sensitive to temperature and pH.
Therefore, it follows that an organism’s body and cells must be maintained at stable temperature and pH levels close to the optimum for the enzymes. The process of maintaining a stable, internal environment is called “Homeostasis”.
As well as regulation of temperature and pH, homeostasis involves the regulation of many other factors such as: • water and salt balance in body fluids. • blood sugar levels.
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• oxygen and carbon dioxide levels.
Feedback Mechanisms A “feedback mechanism” is a situation where the result of some action feeds back into the system to control the next change to the system. In a “Positive Feedback” system any change re-reinforces itself by causing more change in the same direction.
In “Negative Feedback” any change causes the next change to be in the opposite direction. A good example is an oven thermostat control:
Heat ignites more fuel
Turn heater OFF
O
It never results in stability.
If temperature is too high
nh s
Positive Feedback always causes a system to grow out of control, or shrink away to nothing.
ol
Fire grows larger
co
Heat ignites more fuel
n
Fire grows larger
NEGATIVE FEEDBACK ACTION
ve
Produces more heat
Turn heater ON
NEGATIVE FEEDBACK ACTION
produces heat
eat su p
small fire
Ove
For example, a fire growing bigger...
Temperature Sensor (detector)
Negative Feedback causes a system to maintain stability.
If temperature is too low
The result is that the temperature of the oven remains fairly stable. It oscillates up and down a little, but always stays close to the temperature the oven was set at.
Homeostasis is always “Negative Feedback” control. This ensures that stable conditions are maintained so that enzymes are operating near optimum. In animals, it is the Nervous System which is The key parts of a negative feedback system are: largely responsible for carrying out the receptor and control centre functions necessary for many • a receptor, to measure the conditions. aspects of homeostasis. • a control centre, which decides how to respond and • effectors, which carry out the commands of the control centre and make the necessary adjustments to the system. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
In mammals, which maintain fairly constant body temperatures, it is the Hypothalamus at the base of the brain which monitors blood temperature and sends out command messages for negative feedback, rather like the oven thermostat system.
Complete Worksheets 1,2 & 3. Page 6
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2. Temperature Regulation
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Temperature Control in Mammals In a healthy human the internal “core” temperature of the body is about 37oC and is maintained within about 0.5oC at all times. If the body temperature goes up, or down, by more than about 4oC it is a lifethreatening situation. Control of body temperature is achieved as shown in this schematic diagram:
Main Parts of the System The Receptor and Control Centre is the Hypothalamus at the base of the brain. Special cells constantly monitor the temperature of blood flowing by. If the temperature varies by even a fraction of a degree, nerve messages are sent to the effectors. The Effectors include blood vessels, sweat glands, endocrine (hormone) glands, muscles and body hairs. BODY TEMPERATURE REDUCES, BLOOD COOLS p. em d t d e oo ur Bl eas m
to Effectors
Nerve Command
COOLING MECHANISMS Blood vessels dilate. Sweat glands activated. Hair lowered. Metabolic rate reduced.
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Cerebrum
IF BODY TEMPERATURE IS TOO HIGH
llu
m
Hypothalamus monitors blood temperature
Nerve Command
p. em d t od ure Blo eas m
be
to Effectors
re Ce
IF BODY TEMPERATURE IS TOO LOW
WARMING MECHANISMS Blood vessels constricted. Muscles begin “shivering”. Hairs erected (goose bumps). Metabolic rate increased.
BODY TEMPERATURE INCREASES, BLOOD WARMS
What the Effectors Do Blood Vessels Dilation (widening) of veins, arteries and capillaries near the skin allows more blood to flow out near the skin surface. This allows more body heat to escape from the skin, thus cooling the body.
Body Hairs Each hair on your body has a tiny muscle at its base which can cause the hair to stand up erect and give you “goose bumps”. This traps a layer of still air against the skin and helps insulate and prevent heat loss.
If the hair follicle muscle is Constriction (narrowing) of relaxed the hair lies flat and blood vessels causes less allows more heat loss. blood to flow near skin. Less heat flows out to the skin to be lost, so more body Sweat Glands heat is When activated, the sweat glands secrete perspiration. retained. The water evaporates from the skin, carrying away body heat... this has a powerful cooling effect. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Muscles Nerve signals can cause the skeletal muscles to begin “shivering”. This extra muscle activity generates more heat to warm the body.
Hormones are chemicals which control various body functions. The hormone thyroxine (produced by the thyroid gland in the neck) controls the rate of metabolism. It is under the control of the hypothalamus, via another hormone from the pituitary gland. Inspection Copy for Schools only.
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The Temperature Range of Life
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Homeostasis allows an organism to maintain its cells at a temperature close to the optimum for its enzymes. This allows its metabolism to run efficiently, despite changes in the temperature of the surrounding environment. However, homeostasis has its limits, and no organism can remain active and thriving under the full range of temperatures of the biosphere of the Earth. Different organisms have adapted to survive in extreme cold, or in extreme heat, but never both.
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Extreme Heat There are thermophilic bacteria (members of the Archaea) which live and thrive in volcanic hot springs at temperatures up to 120oC. In terrestrial environments such as hot deserts, the temperature can often reach 40oC and sometimes as high as 60oC. Many plants and animals are adapted to survive these extremes, but few remain active in this heat. Generally in deserts the animals seek shelter and become inactive, while plants shut down their metabolism and merely survive.
Cold Water Environments Even when ice forms on the surface, water environments rarely fall below +4oC, and are remarkably stable in temperature. Life-forms do not need to cope with change, although mammals or birds need serious insulation to stay warm. It is the terrestrial environment that is more of a challenge.
Extreme Cold
There are many organisms which can survive extreme cold, but few that remain active. Certain types of algae and photosynthetic bacteria are found to live within the snow and ice near the poles and are still metabolically active at temperatures as low as -10oC. Generally however, plants and animals cannot tolerate their body temperature going below 0oC, since ice crystals forming in cells can destroy membranes and kill cells. Also, the chemical reactions of metabolism run so slowly at low temperature, that life functions are not possible. Of course, many animals do live and survive in the cold because they can produce their own body heat (mammals and birds) and are equipped with body insulation and homeostatic mechanisms to maintain their core temperature despite the cold environment. Perhaps the world champions are the Emperor Penguins which maintain core body temperatures around +33oC throughout the Antarctic winter in air temperatures as low as -50oC.
Temperature Control in Ectotherms Ectotherms are the “cold-blooded” animals, such as reptiles, amphibians, insects, fish, worms, etc. “Cold-blooded” is a misleading term and is best avoided, since these animals are NOT always cold, but rather they rely on the outside environment for their body heat... they do not generate heat internally like a mammal or bird. Ectotherms have a variety of adaptations, many of them behavioural, to regulate their body temperature and keep it within the range in which they can be active; generally 10-30oC. For example, the BlueTongue Lizard will lie in a sunny spot with its body flattened and turned side-on to the INSPECTION Sun on a cool morning. This way it absorbs for schools heat more quickly to get its body temperature high enough to become “Bluey” sun-baking active. As the day becomes hotter, the lizard will turn facing the Sun to absorb less heat, and seek shade to avoid over-heating. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
In prolonged periods of cold weather, such as winter in the Australian Alps, ectotherms cannot remain active. Animals such as the Copperhead Snake and the Corroboree Frog seek shelter underground and become dormant throughout the winter.
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In a process similar to the hibernation of bears, the animal’s heartbeat and breathing slow down, their metabolism almost stops and their body temperature chills to only just above freezing.
As long as they are more than about 50 centimetres underground, the ground will not freeze even though buried in snow for several months. If they haven’t burrowed deeply enough they will freeze to death! Page 8
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Temperature Control in Endotherms Endotherms are the animals which produce their own internal body heat and maintain a constant body temperature... the birds and mammals.
All endotherms rely heavily on having body insulation... fur, feathers or blubber (fat). Humans rely mostly on technology to provide heaters, jackets, wetsuits, gloves, etc, to protect our fragile bodies from extreme temperatures. What do endothermic animals in the wild do? Firstly, they have all the responses for homeostasis described earlier... dilation or constriction of blood vessels, shivering and sweating etc. As well as these, they may have extra adaptations to help regulate their temperature.
In hot environments such as the Australian deserts, mammals such as the Red Kangaroo or the Bilby, have many adaptations to help them cool their bodies: Large ears, with many blood vessels, increases the surface area for heat loss. They seek shade in the heat of the day. Panting evaporates water from the mouth and throat, and cools the blood.
INSPECTION COPY for schools only In the desert, big ears are cool!
They may lick their forearms. The evaporation of saliva cools their body the same as sweating.
In the cold, endotherms go for thick fur coats (Wallaroo) or layers of fat (Australian Fur Seal). Penguins, such as the Fairy Penguins along Australia’s southern coast, have a special “blood shunt” in their legs. In warm conditions the shunt is closed and blood flows normally to the feet. Since the feet are about the only part of their body not well insulated, in cold water they could lose a lot of body heat. So in cold water the flow of blood from body toward the feet is “shunted” via a special vein with a valve in it, back into the body. The feet receive virtually no blood, and this conserves body heat.
Responses of Plants to Temperature Change Plants cannot respond to temperature change by moving away or hiding. To cope with temperature extremes they must have structural or physiological adaptations. To cope with seasonal cold weather, many plants (especially in the northern hemisphere) are deciduous... they shed their leaves and basically shut down their metabolism for the winter, rather like an animal hibernating. Their leaves cannot be protected from freezing, so the strategy is to lose the vulnerable parts, survive until next spring, then grow new leaves. Coping with heat is another story. If there is plenty of water available, such as in a tropical jungle, then the plants cool themselves by allowing maximum evaporative cooling. The leaves open their many stomates and allow transpiration to occur. The evaporation has a cooling effect, in the same way that sweating cools an animal.
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When it is hot and DRY, they have a problem. Desert plants tend to have very small leaves and thick, “stocky” shaped stems. This reduces the surface area being hit by heat radiation from the Sun, and helps prevent over-heating. The cacti plant group have taken the strategy to the limit... their leaves are spines, and stems are “fat” and rounded. They are also light coloured to reflect a lot of the radiant heat away. They have very few stomates. The sclerophyll plants of Narrow, Australia (e.g. gum trees) also drooping have small narrow leaves to gum tree reduce heat absorption from leaves the Sun. Their other “trick” is to allow the leaves to droop. This allows them to catch light for photosynthesis in the cooler morning when the Sun is low, but avoid absorbing heat when the Sun is overhead at midday. They have few stomates, and close them in dry times. Page 9
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3. Internal Transport Systems Internal Transport in Mammals
As with most animals, for internal transport mammals rely on their Circulatory System... the blood, heart and blood vessels; veins, arteries and capillaries. A basic knowledge of how the system operates was covered in Preliminary Topic 2.
Blood You will have examined blood under a microscope and seen something like this:
RED BLOOD CELLS
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You need to be able to sketch diagrams of blood cells, and have an idea of their relative sizes. Sketch of Blood Cells
Size 7 mm
Red Cells
Blood is made of a liquid (“plasma”) with millions of special blood cells carried in it.
There are about 600 red cells to 1 white cell Most white cells are much larger than red cells
no nucleus
Shaped like a donut with the hole closed over
large, irregular nucleus
There are 2 general categories of these cells: Red Blood Cells contain the red pigment haemoglobin, which carries oxygen. This is covered in more detail later in this topic.
White Blood Cells come in a huge variety of types, but all are involved with defence against disease. This is covered in a later topic.
Blood Vessels As the blood flows around the body it is always carried inside tubes, or vessels:
Arteries
carry blood from the heart out to the body tissues. The walls of an artery are relatively thick and muscular to withstand the high pressure in the blood when the heart pumps.
Veins carry blood back from the
body tissues to the heart. The blood here is under lower pressure and the walls of a vein are relatively thin. With little pressure to push blood forward, it is the contraction of the surrounding muscles which helps push the blood along.
Some veins contain valves to prevent back-flow of the blood. Thick, muscular walls
Artery walls are very elastic, and when a pulse of high pressure blood passes through, they expand outwards and then contract again, helping to push the blood along. This rhythmic expanding and contracting is what you can feel as your “pulse” wherever an artery is close to the skin, such as in your wrist or throat.
VEIN Cross-Section
blood flow Relatively thin walls are often squashed by surrounding muscles.
Side view of VEIN showing a valve. Blood can flow one way, but not back the other.
Capillaries are the tiny blood vessels which form a network throughout the tissues so that every living cell is close to the blood supply. The walls of a capillary are only 1 cell thick, so diffusion of substances from blood to cells (or cells to blood) is easily achieved. The inside of a capillary is so small that red blood cells often travel through it in single file. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Substances Carried in the Blood
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Prac Work: CO2 and Acidity
Oxygen O2 is carried in the red
blood cells by haemoglobin.
You will have carried out an experiment to see the effect of dissolved CO2 on the pH of water.
Carbon Dioxide CO2
is partly carried by the haemoglobin in red blood cells, but most of it is carried in the blood plasma, in the form of bicarbonate ions (HCO3-)
You might have chemically produced some CO2 and bubbled it through water. Using a pH meter, or Universal Indicator, you will have measured any change in the pH of the water.
Water is carried as the liquid solvent of blood plasma. Salts, Sugars & Amino Acids
You would have found that the pH went down... i.e. the water became more acidic.
These are nutrients absorbed from the Digestive System. They are generally water soluble and are carried dissolved in the blood plasma.
Lipids (Fats) absorbed from the digestive system are “packaged” in a protein coat which makes the fat molecule miscible in water. This means that, while not fully dissolved, the molecules can be dispersed in water and carried without joining together into droplets of fat and separating from the water.
Explanation and Chemistry Carbon dioxide reacts with water to form carbonic acid CO2 + H2O
Carbonic acid is a weak acid which partly ionises H+
H2CO3
In this form they are carried dispersed in the blood plasma.
Nitrogenous Wastes such as urea, are water soluble and carried dissolved in the blood plasma.
H2CO3
Hydrogen ion makes water more acidic
+
HCO3-
Bicarbonate ion. This is how CO2 is carried in the blood.
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The Need to Remove Carbon Dioxide Carbon dioxide doesn’t just dissolve in water, it reacts to form a weak acid. CO2 + H2O
H2CO3
H+
carbonic acid
It’s the hydrogen ions that create problems. Hydrogen ions are acids and can lower the pH of a cell or the blood. At the concentrations produced by a typical cell, the hydrogen ions could easily lower the pH of the cytoplasm by 0.5 pH unit or more. This might not sound like much, but it could be life-threatening. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
+
HCO3-
hydrogen bicarbonate ion ion
Remember that enzymes are very sensitive to pH changes and quickly change shape and lose their catalytic activity. This would be disastrous for cell metabolism. To avoid this problem, CO2 is carried away in the blood as rapidly as it is produced in the cells. Page 11
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Changes to the Blood as it Circulates
Nutrients & Nitrogenous Wastes As the blood flows through capillaries in the digestive system it picks up sugars, amino acids, salts, water, vitamins, etc that have been absorbed from the gut. (However, lipids are first absorbed into the lymphatic “drains” and enter the blood much later)
This blood from the gut is collected in a vein which takes it directly to the liver. Here some of the nutrients may be absorbed from the blood for storage or chemical processing (e.g. glucose is extracted from the blood and polymerised to form glycogen for storage in the liver). Also in the liver, large amounts of the waste chemical urea is added to the blood to be carried away for excretion. Later, as blood flows through capillaries in body tissues such as muscle or bone, nutrients are absorbed from the blood into the cells which need energy (glucose) and new chemical building blocks (amino acids, lipids). Sooner or later, every bit of blood flows through the kidneys which extract the urea and excess salts and water for excretion as urine.
Respiratory Gases O2 & CO2 Gas exchange and transport is essential for delivering oxygen to cells and removing CO2. CO2
O2 Oxygen Air
Lungs
Carbon dioxide Blood
Air
Blood
Heart CHANGES IN OXYGEN AND CARBON DIOXIDE AS THE BLOOD CIRCULATES
Arteries
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As the blood circulates around the body its chemical composition undergoes a number of changes...
Veins
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Blood flow in Lungs
Oxygen Blood
Arteries
Heart Some Nutrients into storage Wastes into blood
Veins
CHANGES IN NUTRIENTS, WATER & WASTES AS THE BLOOD CIRCULATES
Body tissues
Liver
Digested Nutrients move into blood
Gut
Kidneys Wastes and excess water & salts leave blood. Excreted in urine.
Blood flow in Body tissues Nutrients move from blood into cells
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Carbon dioxide
Cells
O2
CO2
Cells
Blood
As blood passes through capillaries in body tissues, oxygen is released from the haemoglobin molecules and diffuses along the concentration gradient into the body cells. There is always a concentration gradient favouring this because the cells are constantly using up oxygen for cellular respiration. Meanwhile, the concentration of carbon dioxide is high because of its constant production by cellular respiration, so it diffuses from the cells into the blood. When the blood gets to the lungs the opposite occurs. Inside the alveoli (air sacs of the lungs) the air has a very high concentration of oxygen and is very low in CO2. Therefore, oxygen diffuses into the blood, while carbon dioxide diffuses from the blood into the air. Page 12
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The Importance of Haemoglobin
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keep it simple science The high concentration of dissolved CO2 lowers the pH of the blood slightly. This causes the haemoglobin proteins to change shape slightly and release the oxygen molecules.
Blood is red because of the many red cells, and red cells are red because they are packed with the red-coloured, iron-containing protein haemoglobin. In the lungs, where the oxygen concentration is very high, some oxygen dissolves in the moisture lining the alveoli then diffuses into the blood and dissolves in the plasma..
HbO2
Oxygen is not very soluble in water, however, and if that’s all there was to the story, then our blood could never carry enough oxygen to supply our cells. Haemoglobin molecules have a great attraction for oxygen molecules and quickly “grab” any O2 molecules available. Because of this, our blood can carry thousands of times more oxygen than would be possible by simply dissolving oxygen in the blood plasma.
Hb
+
O2
abbreviation for Haemoglobin
HbO2 “Oxyhaemoglobin”
When the oxygenated blood gets to the body tissues the reverse happens.
Hb
+
O2
The oxygen diffuses into the cells, and the freed haemoglobin molecules can pick up some of the CO2 molecules and carry them back to the lungs.
Adaptive Advantage Haemoglobin increases the oxygencarrying ability of blood enormously. Its use in some ancient creature’s primitive circulation system gave that animal a huge advantage to survive. With more oxygen, it could move faster, grow faster and larger and breed more successfully. Many animal types descended from that ancient success. Haemoglobin is a great adaptation.
INSPECTION COPY for schools only
Oxygen Saturation & Its Measurement The concentration of O2 and CO2 in the blood is of great interest to doctors monitoring a patient, or an athlete in training, or even to a pilot or mountainclimber at high altitude. The most important measurement is “percentage oxygen saturation” (%SpO2). A reading of 100 would mean that 100% of all haemoglobin in an artery is totally saturated with oxygen. Readings between 95-100% indicate good health, fitness and adequate oxygen supplies. Lower readings (e.g. 80%) could indicate: • respiratory or circulatory problems in a patient. • lack of fitness, or excessive exertion in an athlete. • need for supplementary oxygen for a pilot or climber. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
In years gone by, %SpO2 was measured by taking blood samples and carrying out complex chemical testing. With modern technology, however, the readings are done instantly and non-invasively by a small, portable instrument clipped onto the end of a finger, ear lobe or foot. The “Oximeter” works by sending red light and infra-red beams through the flesh. The amount of each light absorbed by the haemoglobin gives a direct measurement of %SpO2, because haemoglobin with, or without, Foot-clamp Oximeter measures oxygen %SpO2 in a young patient absorbs these light beams differently.
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Products of Blood Donation
keep it simple science The Australian Red Cross Blood Service collects about a million blood donations per year. Most of this blood is used for people who need regular treatment with blood products for conditions such as leukemia. Only a very small amount is kept as whole blood for emergency transfusions. Most donated blood is separated into about 20 different fractions or products, so each donation can treat many different patients. The main blood products are:
Red Cell Concentrate
Plasma
which contains about twice as many red cells as normal, is used to boost the oxygen-carrying capacity of patients with anaemia or after blood loss, such as might happen in a motor accident.
is the liquid part of the blood and is often given in emergency to boost the volume of blood following severe blood loss.
Cryoprecipitate is a fraction collected from plasma and contains blood-clotting factors. It is used to treat severe bleeding.
Platelet Concentrate is given to patients who need extra blood-clotting capability, such as leukemia sufferers, or following severe blood loss.
Factor VIII and Monofix are extracts from plasma used to treat people who have haemophilia... an inherited, incurable disorder in which the blood will not clot properly. These blood products allow patients to lead a relatively normal life.
White Cell Concentrate is given to patients needing a boost to their immune system, perhaps following a severe infection.
Artificial Blood? The Need for Artificial Blood Fresh blood cannot be stored for long, and many parts of the world lack the necessary storage facilities. Many blood products can set off immuneresponses in long-term patients, even after correct blood-typing. (Similar to “rejection” of a transplanted organ) Donated blood can carry diseases, such as hepatitis or HIV. Many of these problems could be solved by the use of an artificial blood which is easy to store and can be made disease-free.
INSPECTION COPY for schools only Haemoglobin-Based Oxygen Carriers is one of the areas of current research. Haemoglobin extracted from animal blood can be purified and treated so that it is disease-free and cannot cause any allergic or “rejection” responses in patients. The products can be stored for years at room temperature, and promise to be highly effective at carrying oxygen and releasing it into the tissues. Currently undergoing clinical trials, but not yet approved for medical use. Recent trials failed.
Perfluorocarbon-Based Substitutes Another area of research aims to develop a truly artificial blood substitute. The most promising base chemicals are the “perfluorocarbon” compounds. These can carry up to 5 times more oxygen than blood and can be stored indefinitely at room temperature. They can be made totally sterile and disease-free. At least 5 different products are being tested and trialled (USA), but none are yet approved for medical use. Trials in 2008 produced very negative results. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Page 14
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keep it simple science
Transport Systems in Plants Hollow, dead cells, joined end to-end forming a tube
Xylem Tubes Carry Water Xylem tubes are dead, hollow cells, joined endto-end forming a continuous tube from root to leaf. The xylem tubes transport water (and dissolved minerals) generally upwards from roots to leaves.
INSPECTION COPY for schools only
Cell walls re-inforced with rings and spirals of lignin
Photo at left: Scanning Electron Microscope (SEM) image of plant stem showing hollow xylem tubes. Creative Commons Attribution-Share Alike 3.0 unported licence. Image by McKDandy at en.wikipedia.
How do xylem tubes lift water upwards against the force of gravity?
“Transpiration” is the evaporation of water from the leaves. When the stomates are open, water can constantly evaporate, creating a tension, or “pull” in the remaining water in the leaves. Water molecules are quite strongly attracted to each other and tend to cling tightly together. This force is called “cohesion” and is the reason that water tends to form droplets... little blobs of water that cling together. So, when water evaporates from leaves and creates a “pull” force, each water molecule pulls on those behind it because of the cohesion. Each molecule pulls others upward and so the entire column of water in a xylem tube moves upwards to replace the water lost by transpiration. So water is pulled upwards by a combination of transpiration and cohesion. This flow is called the “transpiration stream”.
Cohesion & Adhesion Another factor which helps the process is called “capillarity” or the “capillary effect”. This is the way that water can “climb up” the walls of a container forming a meniscus in a test tube, for example. This happens because water molecules are not only attracted to each other (“cohesion”) but also to some other substances such as glass or the inside of a xylem tube. This attraction is called “adhesion”. In very narrow tubes (“capillaries”) the water will climb upwards against gravity because of adhesion, and drag more molecules along by cohesion. This happens in xylem and helps lift water upwards. The “veins” in a leaf contain both the xylem & phloem tubes. Veins also act as “ribs” to help keep leaves in shape.
Active & Passive Transport Note that the flow of water in the xylem costs the plant nothing in energy terms... it is “passive” transport. In contrast, the other transport system in plants is an “active transport” system... the plant must constantly supply energy to make it happen.
Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Phloem Tubes Carry Food Nutrients
While the xylem tubes are formed from dead cells, the phloem are living cells joined end-to-end. The ends of each cell are perforated (“sieve plates”) so each cell is open into the next and they form a continuous tube.
The transportation of nutrients through the Phloem Tubes is called “Translocation”. Sugars are actively transported in the flow of cytoplasm within the cells.
INSPECTION COPY for schools only
Sieve plate between cells.
PHLOEM CELL alive and filled with cytoplasm. Flow of cytoplasm carries sugars through each cell.
Translocation Works 2-Ways While the xylem is a one-way flow system, the phloem system can carry food (especially sugars) in either direction.
“Companion cell” has many mitochondria to provide ATP to the phloem cell
If a lot of photosynthesis is occurring, the phloem will carry sugar to storage sites in roots or stem. If photosynthesis is not possible for an extended time, then the phloem will carry sugars back from the storage sites to feed the leaf cells, or supply a growing flower or fruit.
After this page, complete worksheets 6, 7, 8, 9 & 10.
What Makes the “Sap” Flow? The flow of nutrients through the phloem is caused by pressure differences between the “Source” tissues and the “Destination”.
Sugar is carried into cells by active transport, requiring energy. Water flows in due to osmosis, raising the pressure.
SOURCE Higher Pressure PH
The pressure difference is osmosic pressure, generated by active transport of sugars causing water to flow into, or out of cells.
LO
Translocation... how it works
EM TU ca
S
slo
BE
n Tra
tio
Sugar solution flows due to pressure differential
n
Sugar is removed by active transport, requiring energy. Water flows out of cells due to osmosis, lowering the pressure.
DESTINATION Lower Pressure
The “veins” in a leaf are bundles of tubes with both xylem AND phloem. There are also many strong fibres which add strength and help keep the leaf in shape so it gathers light without “drooping”. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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4. Excretion & Water Balance The Importance of Water
Life cannot exist without water. All living cells are at least 75% water. The functions of water in living things include:
Water is the Solvent of Life All the chemical reactions of metabolism take place in water solution, and the transport of materials in cytoplasm, blood or phloem takes place mainly in water solution.
Water Regulates Temperature Water has a very high specific heat capacity. This means it can absorb (or lose) relatively large quantities of energy with minimal temperature change. This helps stabilise the temperature of all living things. Water also has a very high heat of vaporisation. This means that when it evaporates it absorbs huge amounts of heat. This is why evaporation of perspiration from the skin has such a cooling effect.
Water Supports & Cushions Cells & Organs Many plants and animals rely on water for body support. Non-woody plants pump their cell vacuoles full of water to make cells “tight” and keep stems and leaves upright. Animals such as worms rely on the hydraulic pressure of water in their tissues to support their body and maintain its shape. In vertebrate animals the water solutions in the tissues helps to cushion organs against bumps and impacts. (e.g. cerebrospinal fluid around the brain)
Water is Involved in Life Chemistry Water is a reactant or product of many metabolic reactions. The reactions of photosynthesis and cellular respiration are just two of the many examples.
Homeostasis of Water & Salts It’s not just the water that is important, but its concentration, and the concentration of substances dissolved in it, such as salts. If the concentrations are not kept at the correct levels, then osmosis may cause problems. Cells could lose water and dehydrate, or gain too much water and be damaged or even burst open by increasing pressure within.
Major Internal Organs in a Human INSPECTION COPY for schools only
Lungs Heart
THE CONCENTRATION OF WATER & DISSOLVED SALTS MUST BE MAINTAINED
Liver Stomach
Kidney
THIS IS ANOTHER EXAMPLE OF HOMEOSTASIS Ureter
IN MOST ANIMALS WATER BALANCE IS REGULATED BY THE KIDNEYS Bladder
Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Kidneys Also Excrete Metabolic Wastes
®
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INSPECTION COPY for schools only
Metabolic Wastes
The many chemical reactions of metabolism sometimes produce chemicals which are toxic to cells, often because the chemical, when dissolved in water, can change the pH and reduce enzyme activity. Therefore, it is essential that these wastes are removed (“excreted”) as soon as possible. The major wastes are:
Nitrogenous wastes (contain nitrogen) These wastes are produced mainly from the metabolism of proteins. There are 3 main compounds that can be produced:
Ammonia in most aquatic animals. Uric acid in birds, reptiles & insects.
Carbon dioxide is produced by cellular respiration. As covered previously, it will lower the pH (it’s acidic). It is carried in the blood and excreted by the lungs.
Urea in mammals and amphibians.
Excretion & Water Balance in Fish Fish produce the waste ammonia which is very alkaline and toxic. Luckily it is very soluble in water. Since they live surrounded by water, fish simply excrete ammonia from their gills by simple diffusion. Their kidneys are used not so much for excretion, but for maintaining their water balance. Freshwater fish and saltwater fish have opposite problems with water balance.
SALTWATER FISH Constantly drink to replace water (but get salt, too)
FRESHWATER FISH
Water loss from tissues by osmosis (mainly through gills)
Gills excrete Ammonia, Carbon Dioxide and excess salt
Kidneys produce small amounts of urine to save water
Tissues gain water by osmosis (mainly through gills) Do not drink Gills excrete Ammonia & Carbon Dioxide, and actively absorb salts
Kidneys produce a lot of dilute urine to remove water from body
Excretion in Terrestrial Environments The fish can get away with production of highly toxic ammonia. They can rely on constant diffusion of ammonia from the blood in their gills into the water environment which surrounds them.
Consequently, in land-living animals nitrogenous wastes are produced not as ammonia, but the less toxic compounds urea (mammals) or uric acid (birds, reptiles, insects).
In terrestrial environments, waste gases can do exactly the same; that’s how carbon dioxide is excreted... by simple diffusion from the blood to the air in the lungs.
Excretion is via the kidneys. The simple processes of diffusion and osmosis are not adequate to achieve this.
However, nitrogenous wastes are not gaseous and need to be excreted in water solution. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
For simple diffusion to achieve excretion it would require huge amounts of water to be excreted too, and no terrestrial animal can afford to lose so much water, especially in a desert. Page 18
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KISS Resources for the NSW Syllabus.
How the Kidneys Work in Mammals
®
keep it simple science Each kidney contains about 1 million nephrons. Each nephron is a complicated tangle of blood vessels and renal tubules (= small tubes). What happens in a nephron is:
Artery carries blood into kidney.
Vein carries blood out of kidney.
Filtration removes some of the water and many small dissolved molecules (including the waste urea) from the blood into the renal tubules. This occurs because the walls of the glomerulus are “leaky” and the blood is under high pressure.
Reabsorption then occurs to move useful substances back into the blood. This is achieved by: Active Transport of sugar, amino acids & salts from the renal tubules back into the blood. This requires energy to be used to transport these chemicals across the cell membranes, against a concentration gradient. Osmosis then occurs, which causes water to flow from the tubules back into the blood. This is Passive Transport and costs the body no energy.
Bladder stores urine.
Ureter carries urine to bladder.
Urethra drains urine from bladder.
Renal Tubules
Glomerulus a coiled blood vessel
Kidney removes wastes from blood and adjusts water & salt balance.
THE NEPHRON of the KIDNEY (simplified)
Blood in from artery. This blood contains urea
Filtration occurs here
Bowman’s Capsule a “receiving cup” to collect the filtrate liquid from the blood
Reabsorption occurs here
Urine flows to collecting duct
Blood Capillary Network shown in simplified form.
Blood out to vein This blood has had wastes removed, and water balance adjusted for Homeostasis.
Filtration is the process in which some water and many dissolved substances (including sugar, salts & urea, BUT NOT any cells or blood proteins) leave the blood and flow into the renal tubules.
then via Ureter to Bladder, for excretion.
INSPECTION COPY for schools only Reabsorption is the process in which
any useful substances (such as sugars & amino acids) are absorbed back into the blood. Water & salts are also reabsorbed, but in varying quantities... the body is adjusting water balance for Homeostasis
Urea is not reabsorbed back into the blood. Urea and some water continue along the tubule. This liquid is URINE. Urine flows into the Ureter and is carried to the Bladder for storage. When the bladder becomes full, the urine is excreted via the Urethra. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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The Kidneys & Homeostasis
®
keep it simple science The kidneys are not just used for excretion. As well, the kidneys can adjust the “water balance” of the body by allowing more, or less, urine to be produced. In this way the kidneys are a vital part of homeostasis. Once again, the Hypothalamus is involved, but the control mechanism is by hormones... chemicals which are released into the blood and exert a control function on some “target organ”. In this case the hormone is called “Anti-Diuretic Hormone” (ADH) and the target organ is the kidney, specifically the nephron tubules. BODY RETAINS MORE WATER, excretes less urine. Urine is more concentrated
ADH causes more reabsorption of water from kidney tubules Note the typical pattern of a negative feedback system
c lan a b alt u r e d S / s ter e a Wa m
Cerebrum
n ala b t d al r e r/S a s u e t e Wa m
BODY PASSES MORE WATER, excretes more urine. Urine is more dilute.
Ce
re
ll be
WATER LEVEL IN BODY TOO HIGH
um
ce
HYPOTHALAMUS & PITUITARY GLAND
Less ADH causes less reabsorption of water from kidney tubules.
to Pituitary Gland
WATER LEVEL IN BODY TOO LOW
e
Nerve Command
to Pituitary Gland
Nerve Command
Pituitary Gland releases more ADH (Also nerve signals to brain cause “thirsty” feeling so you will want to drink)
Pituitary Gland releases less ADH (Also nerve signals to brain cause feeling that you do NOT want to drink)
Kidney Structure & Nephrons Practical Work You may have dissected a kidney in your laboratory work in class.
DISSECTED KIDNEY
You need to be able to relate the gross structure of the kidney to the structure and functioning of the nephrons.
Renal Cortex Dark red in colour due to the many blood capillaries of the nephrons Medulla Lighter in colour... less blood vessels. Here many collecting ducts carry urine to the ureter.
This diagram may help you understand your kidney dissection a little better.
Artery & Vein
INSPECTION COPY for schools only Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Ureter carries urine to bladder Page 20
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Water & Salt Balance Hormones
®
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The hypothalamus monitors the blood flowing through it for the “osmotic balance” of water and dissolved salt. If the body is even slightly dehydrated, more ADH is released by the pituitary gland and circulates in the blood stream. The effect of ADH is to alter the permeability of the membranes lining the tubules of the kidney nephrons. Increased ADH levels make the membranes more permeable to water, so more water is reabsorbed back into the blood. This means that less urine is produced. If the body is over-hydrated, the production of ADH is reduced. This causes the tubules to become less permeable to water so less is reabsorbed into the blood. The result is more urine being produced. ADH is the hormone controlling the water levels, but this is only part of the “osmotic balance” story... the salt levels can be controlled too... see below.
INSPECTION COPY for schools only
Control of Salt Levels by Aldosterone Sitting on top of the kidneys are the “Adrenal Glands” which produce a variety of hormones. One of the adrenal hormones is Aldosterone which controls reabsorption of salt from the nephron tubules.
Adrenal Gland
If salt levels are too low, special cells in the adrenal glands increase the production of aldosterone into the bloodstream. This causes the cells lining the nephron tubules to actively transport more sodium ions back into the blood. Chloride ions follow the sodium, and so more salt is reabsorbed. If salt levels are too high, the adrenal glands produce less aldosterone so less salt is reabsorbed, and the excess salt is excreted in the urine. Between ADH and aldosterone the body maintains a constant “osmotic balance” of water and dissolved salt... Homeostasis. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Addison’s Disease & HRT Addison’s Disease occurs when a person’s adrenal glands do not produce enough aldosterone. Their nephrons constantly fail to reabsorb salt and so the “osmotic balance” of the body is chronically out of order. This leads to a variety of problems and malfunctions throughout the body involving the heart, intestines and liver, and may cause psychological disorders as well. This is a disease that can be sucessfuly treated by “Hormone Replacement Therapy” (HRT). A person with Addison’s Disease can be treated with appropriate doses of steroid hormones (usually cortisone) and although they cannot be totally cured, they can lead a normal, symptom-free life on HRT.
Page 21
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Renal Dialysis
If a person’s kidneys cease functioning properly he/she can no longer remove toxic wastes such as urea from the blood, nor maintain homeostasis of “water balance”. In the case of complete kidney failure, this condition can be fatal within about 3 days without treatment. Dialyser cartridge Over the past 40 years or so, many people have been successfully treated by receiving a kidney transplant. However, they may have to wait months or years to find a suitable organ donor. Meanwhile, they need to be treated by Renal Dialysis... the use of medical technology to remove wastes from the blood artificially. In effect, a renal dialysis machine is an “artificial kidney”.
Dialyser Cartridge
Blood in
The key component of a modern dialysis machine is a disposable dialyser cartridge. The patient’s blood flows through the cartridge from one end to the other inside thin “dialysis tubes”. These tubes are made from a plastic which is semi-permeable. Dialyser cartridge
INSPECTION COPY for schools only
The tubes are surrounded by a “dialysing fluid” which flows through the cartridge in the opposite direction.
Dialysing fluid out Blood flows through dialysis tubes Dialysing fluid in
The dialysing fluid Blood out contains water, salts, sugars, minerals etc exactly as in healthy blood plasma. Since there is no concentration gradient for these chemicals they do not diffuse in or out of the blood. However, the wastes such as urea are in higher concentration in the blood, and so they diffuse from the blood into the dialysis liquid, which is later disposed of.
Comparison of Renal Dialysis with Natural Kidney Function Differences Similarities •Both processes remove urea and other wastes from the blood.
• Kidney function involves the 2 steps of filtration and reabsorption; dialysis involves only 1 step of diffusion of wastes from blood.
•Both rely on movement of dissolved substances through semi-permeable membranes.
• In a kidney, movement across membranes is achieved by both active transport and by passive osmosis and diffusion; dialysis involves only passive diffusion.
Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Water Balance in Australian Animals
keep it simple science The different conditions of each environment dictate what an animal must do to to achieve homeostasis of its “water balance”. In each environment there are different problems to be overcome, and the animal’s body organs must respond appropriately. Exactly how homeostasis is achieved will be reflected in the urine the animal produces.
Urine Production in Different Environments Comparison: Marine Fish
problem: constant loss of water by osmosis. urine: small amount, to conserve water. Urine does not contain wastes, since ammonia is excreted from the gills.
Freshwater Fish problem: constant gain of water by osmosis. urine: large volume, to remove water. Urine does not contain wastes, since ammonia is excreted from the gills.
Water Conservation & Excretion in Insects
All insects are small, and most are adapted for flight. This means they cannot afford to carry large amounts of water in their bodies just for the purpose of excreting urine. Their excretory system must be able to remove nitrogenous wastes, while losing only a minimum of water. Firstly, their nitrogenous wastes are processed chemically into the form of uric acid, which has a low solubility in water. This means that, when their urine is separated from the blood (filtration) and then concentrated by reabsorption of water, the uric acid precipitates as a solid. After further reabsorption of water, the insect’s urine is a semi-solid paste, which is passed into the rectum and excreted with their solid digestive wastes. The Malpighian Tubes are the insect equivalent of kidneys
Intestine
Terrestrial Mammal problem: must excrete wastes in urine, but cannot afford to lose too much water, especially in dry Australian ecosystems. urine: generally small volume, to conserve water. Urine is relatively highly concentrated in wastes such as urea.
ANUS MOUTH MALPIGHIAN TUBES extend through insect’s body, collecting and concentrating urine. Urine is emptied into the gut for excretion.
INSPECTION COPY for schools only
Water Conservation & Excretion in Australian Mammals They achieve this by:
Many Australian environments are desert or semi-arid and water conservation is vital for survival. Some adaptations for temperature control, while conserving water, were covered earlier in this topic. Many Australian mammals have excretory systems that also contribute to water conservation, while managing to efficiently remove their nitrogenous waste, urea. The desert-living Red Kangaroo, the Spinifex Hopping Mouse, and even the Koala (which rarely drinks) all have the ability to produce very small amounts of highly concentrated urine. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
• having longer tubules in their kidney nephrons, which allows for more reabsorption of water back into the blood, thus less urine is produced. • the cells lining the tubules are able to actively transport urea from blood into the urine. So, not only is urea not reabsorbed from the “filtrate” liquid, but is actively “pumped” from the blood. The result is less water and more urea in their urine. Page 23
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Enantiostasis
Enantiostasis is a special case of homeostasis. It refers to the maintenence of metabolic and physiological functions, (i.e. homeostasis) despite significant variations in the surrounding environment.
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An important example is an estuary, where river meets sea. Organisms are able to maintain their water and salt balance, despite wild fluctuations in the water and salt concentrations around them, every time the tides change.
Examples of how they do this are: Crabs & yabbies burrow into the mud, where the salt concentrations are more stable. Oysters close their shell, to avoid extreme conditions they cannot cope with. Estuary fish, like bream, switch their excretory systems from water conservers when it’s salty, to water excreters when it’s fresh.
Water Conservation in Australian Plants The characteristics of Australia’s sclerophyll plants were dealt with in the Preliminary Course topic “Evolution of Australian Biota”. In summary, the sclerophyll plants include the gum trees, banksias and acacias (wattles) and all show numerous adaptations to conserve water in our arid climate, such as: • Small, narrow, drooping leaves with thick, waxy cuticles. • In dry times, gum trees shed many of their leaves so that there are less surfaces for evaporation. • Species such as Spinifex grass limit evaporation by having fine hairs all over their leaves. This traps a layer of air near the leaf so that wind cannot increase evaporation rates. • Generally, all Australian sclerophylls have fewer stomates on their leaves to limit the water loss from transpiration.
GUM LEAVES
Small & narrow to reduce Surface Area for less evaporation
How Plants Cope With Salt Many of the Australian coastal estuaries are home to Mangrove trees which have a number of adaptations to cope with the salt water that covers their roots with every high tide. To maintain their “osmotic balance” they must both conserve water and deal with high levels of salt.
Mangroves in coastal NSW
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One of the most common species is the “Grey Mangrove”, Avicennia marina, which has all the following adaptations: • Leaves with a thick, waxy cuticle and fine hairs on the undersurface, all to minimise water loss. • Salt glands in the leaves which excrete a concentrated salt brine onto the leaf surface. The salt gets washed away when it rains.
Thick, waxy cuticle minimises evaporation Droop downwards to avoid the heat of midday for less evaporation Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
• Salt is deposited in older leaves, so when they drop off they carry a load of excess salt away. • Special tissues within their roots which allows water to pass through, but reduces the passage of salt. This helps to reduce the salt intake. Page 24
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Complete Worksheets 11,12,13 & 14.
KISS Resources for the NSW Syllabus. ®
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Worksheet 1 Enzymes & Homeostasis
Fill in the blank spaces. The total of all the chemical reactions in an organism’s body is called a)........................................ Each reaction requires a catalyst, which is a chemical which b).................................... the reaction, without being c)............................................... itself. Biological catalysts are called d)................................. These have the following properties: They are molecules of e)................................., which are polymers of f)...................... ......................... Each one has its own unique g)................................., which perfectly fits the molecule(s) of the reaction. These molecules are referred to as the h)..................................... Because each enzyme only fits its own particular h)..............................., they are said to be i).................................................... Enzymes will only work effectively in a narrow range of j).................................. and k).................... This is because their l).................................. changes so that they no longer fit their substrate. The pH scale is a numerical measurement of m)........................ and n)........................................ Things that are neutral have a pH= o)............. Acids have pH values p).................... 7, while alkalis (bases) have pH q)..........................
Worksheet 2
Name....................................
The pH inside living cells, and in most parts of an organism’s body is about r).............., but an exception is the s)............................... which is quite strongly t)..................................... Homeostasis is the process of keeping an organism’s internal environment u)........................... The factors that need to be maintained include v).................................. and w)................ as well as x)............................. and salt balance, y).......................................... levels and oxygen and carbon dioxide levels. Homeostasis involves z)........................ feedback. The 3 parts of any feedback system are the aa)..........................., which measures or monitors conditions, the ab)........................................ which decides how to respond and issues commands, and the ac).................................... which carry out the commands. In animals generally it is the ad).......................................... system which is largely responsible for monitoring and control. In mammals, homeostasis of body temperature is controlled by the ae)........................................... at the base of the af).................................
Enzyme Activity Graphs Name....................................
1. Sketch the shape of a graph of Enzyme Activity against Temperature.
3. Sketch a graph of Enzyme activity against pH. 4. Explain why the graph shows a “peak” of optimum activity at a certain pH.
5. Why does activity decline at pH values higher or lower than the optimum? 6. Sketch a graph of enzyme activity against substrate concentration.
2. Explain the shape of the graph; 7. Explain a) at temperatures below the “optimum a) why the graph rises
b) at temperatures above the optimum.
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b) why the graph levels off
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Worksheet 3 Test Questions
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Multiple Choice 1. Which of the following is NOT true about enzymes? Enzymes:A. are catalysts which speed up chemical reactions. B. are carbohydrate molecules of a special shape. C. only work within a narrow range of temperature. D. only works for one substrate... “specific”.
3. At point D on this graph, you could describe the enzyme as: A. saturated with substrate. B. optimum shape. C. decomposed. D. denatured.
Name....................................
6. The effect on enzyme activity of increasing the substrate concentration is best described as: A. Activity rises to an “optimum”, then declines. B. Activity always continues to rise. C. Activity declines as concentration increases. D. Activity rises, then levels off.
Longer Response Questions Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. Answer on reverse if insufficient space.
7. (4 marks) Discuss the importance of shape to the characteristics of an enzyme, with specific reference to: a) why each enzyme will usually only catalyse only one reaction.
D Temperature
Enzyme Q Enzyme P Enzyme Activity
4. This graph compares the performance of 2 enzymes at different pH levels.
Rate of reaction
The graph shows the rate of an enzyme-catalysed reaction. Questions 2 and 3 refer to it. B 2. Which part of this graph (A,B,C or D) corresponds to C the enzyme having the best 3-dimentional shape to fit its substrate? A
section 1
b) why enzymes only work within fairly narrow ranges of temperature and pH.
8. (8 marks) The following data was collected in an experiment in which the time taken for a chemical reaction catalyzed by an enzyme, was measured at different temperatures. o Temp ( C) Time taken for reaction (min.) 5 4.0 10 2.0 15 1.0 20 0.2 25 2.5 30 10 a) Tabulate this data appropriately, adding a third column for “Reaction Rate” and calculating values for this.
1 2 3 4 5 6 7 8 9 10 pH
b) Construct a graph of Temperature v Rate.
It would be reasonable to conclude that: A. “P” is a stomach enzyme, “Q” is intra-cellular. B. “P” is from a plant cell, “Q” is from a mammal cell. C. “Q” performs better than “P” under all conditions. o D. Both would have optimum activity at about 40 C.
c) Is it likely that this is a human enzyme? Explain.
5. Which of the following is least likely to be controlled by a negative feedback system? A. Body temperature B. Blood sugar levels C. Rate of digestion D. Water & salt INSPECTION COPY levels.
b) What is the link between the necessity for homeostasis and enzymes?
9. (5 marks) a) What is meant by “Homeostasis”
c) Using a simple example, explain the concept of “negative feedback” as a way to maintain stability of any system.
for schools only
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Worksheet 4 Temperature Regulation
Fill in the blank spaces. Temperature regulation in mammals is controlled by the a)..................................... at the base of the brain. If body temperature is too high it sends commands to the b)..................................... organs to cool the body. Cooling mechanisms include c)............................ of blood vessels to allow d)................... (more/less) blood to flow near skin. Also, the e)............................ glands may be activated, allowing f)......................... to flow. As it g).............................. from the skin, it carries heat away. Metabolic rate may be reduced, to reduce heat production. This is achieved by h).......................... which are control chemicals. An example is Thyroxine, produced by the i)....................................... gland. If the body is too cool, then the hypothalamus commands various warming mechanisms. Blood vessels can be j).................................... to reduce blood flow to k)...................... Body hairs are l).............................. to trap a layer of still air, which acts to m).................................. better. Nerve commands to muscles can cause them to n)............................. which produces extra heat. The metabolic rate can be raised by hormones as well. Animals which rely on the environment to supply their body heat are called o)........................................ Examples are p)............................, amphibians, fish etc. In terrestrial environments they often seek or avoid the heat of the q)................ in order to regulate temperature. An Australian example is the r)............................, which often s)......................... in the morning to warm up, and t)..................................... when too hot. In cold winters, ectotherms cannot get any heat from the environment and many, such as the u)..................................... survive by v)................................. for the winter. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Name....................................
Animals which can regulate their body temperature are called w).............................. Examples are the x)......................... and y).................. They use all the homeostasis techniques, plus rely on body insulation with fur, z).................... or aa)..................... In extreme environments endotherms may have extra adaptations. In Australian deserts many animals have large ab).................... to radiate heat away. They don’t have sweat glands because they can’t afford to ac).......................................... but may lick their ad)............................... or pant to achieve some evaporative cooling. In cold environments, thick fur or blubber gives ae)...................................... to retain body heat. The penguins have a special adaptation in the blood vessels to their legs. In cold water, the blood flow to the feet is af).................. ...................................... so that less heat is lost through the uninsulated feet. Plants also have many adaptations to cope with temperature extremes. In cold climates many plants are ag).............................. which means they ah)............................................ in winter. In hot climates with plenty of water, plants open their ai)............................ allowing evaporation to cool them. In dry climates, plants cannot afford the water loss, so they stay cool without losing water. For example, cacti have aj).......................shaped leaves to reduce the surface area absorbing heat from direct sunlight. They are often ak)...........................-coloured to reflect heat radiation. The Australian al)................................... plants mostly have am).................................. (shape) leaves to reduce surface area, and often allow the leaves to an)......................... (orientation) to avoid the Sun’s heat at midday.
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Worksheet 5 Test Questions
Multiple Choice 1. The “control centre” for homeostasis involving the nerve system is the: A. Hypothalamus B. Cerebrum C. Cerebellum D. Pituitary gland 2. Which of the following is a response by an effector organ which would be appropriate when the body is too warm? A. Muscles begin shivering. B. Blood vessels dilated. C. Body hairs erected, forming “goose bumps”. D. Metabolic rate increased by a hormone. 3. Which statement is correct? A. Ectotherms such as fish, generate their own body heat. B. Endotherms such as birds, rely on their surroundings to supply their body heat. C. Ectotherms such as mammals, generate their own body heat. D. Ectotherms such as reptiles, rely on the surroundings to supply body heat. 4. A typical response of an ectotherm to over-heating is: A. sweating B. sun-baking C. seeking shade D. shivering
section 2
Longer Response Questions 6. (8 marks) a) Discribe the role of the hypothalamus in the regulation of body temperature in a mammal.
b) Give an outline of how the blood vessels function as “effectors” in the regulation of body temperature.
c) List 3 other effectors (apart from blood vessels) involved in temperature regulation.
7. (6 marks) a) Explain the difference between an ectotherm and an endotherm.
b) Using a named Australian example, outline how an ectotherm regulates its body temperature.
c) Using a named Australian example, outline 2 adaptations of desert-living endotherm to keep their bodies cool.
5. An important adaptation in Australian mammals to help keep cool in a desert environment is: A. a lot of sweat glands in the skin. B. a “stocky”, thick-set shape to minimise heat absorption. C. large ears to acts as heat radiators. D. thick fat layers to prevent heat getting into their body.
Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Name....................................
INSPECTION COPY for schools only 8. (3 marks) Describe some adaptations of sclerophyll plants which help them minimise absorption of heat from the Sun.
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Worksheet 6 Transport in Animals
Fill in the blank spaces. Blood is made up mainly of a liquid called a).......................... and many blood cells. The most numerous blood cells are the b)........................... which contain the protein c)............................. responsible for carrying d).............................. gas. Most of the carbon dioxide in blood is carried in the form of e).................................... ions. These are made when carbon dioxide reacts with f)................. forming g)........................ acid. Most other substances carried in blood are dissolved in the h)................................. This includes nutrients such as i)......................... and j)................................., water and salts, and the nitrogenous waste k)......................... Lipids (fats) are first wrapped in a coating of l)............................ so they can be dispersed without separating. There are 3 types of blood vessels: the m)................................... have thick muscular walls to withstand the high n)...................... of the blood being pumped from the o)..................................
Worksheet 7
Name....................................
p)................................ have thinner walls, and have q)................... along their length to prevent blood r)..................... ............................ Capillaries have walls which are s).................................. thick and form a network throughout the body’s t)......................... As the blood flows around the intestines it picks up u)..................................... It then flows straight to the v)................................, where some nutrients are removed for w)....................... & ............................, and wastes such as x)..........................are added. These wastes are later removed from the blood by the y).................................. and excreted with any excess z)........................ & ...................... as urine. Meanwhile, when blood flows through the capillaries of the lungs, aa)........................... gas is absorbed into the blood and ab).............................. gas is released from blood into air. When blood flows through the body tissues, nutrients move from ac)........................ to ad)................................. as does ae)............................... gas, while af)..................................... gas moves the other way.
Blood Chemistry
Name....................................
Answer the following questions.
1. Write 2 chemical equations to summarise how carbon dioxide reacts with water.
3. With reference to one of the equations in Q1, explain why it is essential to quickly remove CO2 from body tissues.
INSPECTION COPY for schools only 4. With reference to one of the equations in Q1, explain how the oxygen release from blood cells to body tissues is facilitated. 2. Name the chemical form in which most CO2 is carried in the blood.
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Name.................................... Worksheet 8 Haemoglobin & Blood Products
Fill in the blank spaces. Oxygen is carried by the a)...............coloured, b).....................-containing protein called c)....................................... It has a great affinity for oxygen molecules, and each molecule can absorb d)............. (number) oxygen molecules, in which form it is called e)..............- ....................................
Most blood donated to the “Blood Bank” is separated into different fractions for different uses. Some of the main blood products are: n)..................... Cell Concentrate, to boost O2-carrying capacity. White Cell Concentrate, to boost o)..............................
In the body tissues, the presence of f).................................... gas lowers the pH slightly, which causes haemoglobin to change shape slightly and g)......................... the oxygen, which then h)............................. into the cells.
p).......................... Concentrate, to help blood clotting.
The “%SpO2” is a measure of the i)........................................... in a person’s blood. Good health, fitness and adequate oxygen supply are indicated by readings above j)..............% This can be easily measured by a k)......................................... which sends beams of l)..................... & ...................... through a finger or ear-lobe. Oxygen saturation is measured according to how much of each type of light is m)....................................... by the blood.
Research is going on into developing artificial blood. This is needed because fresh blood cannot be s)......................... for long, and can cause t)................................. in some patients, There is also a danger that donated blood might carry u)...............................
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Worksheet 9
q)....................., which is the liquid part of the blood, used in emergency to increase r).........................................
Two of the areas of research for artificial blood are: v).......................... -Based w)..................... Carriers, made from animal blood, and completely artificial substitutes based on the chemicals called x)......................................................
Transport in Plants
Fill in the blank spaces. Transport in plants is carried out by 2 separate systems. The a)........................... tubes carry water and dissolved minerals from the b)..................... to c)........................ These tubes are d).............................. (dead or living) cells. The transport is e)................................. (active or passive) and the movement of water is called f)................................................. Basically the process works because, as water g)..................................... from the leaves, this “pulls” water up from above Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Name....................................
because water molecules are h)............................. and cling together. Meanwhile, the i)..................................... vessels carry out j)....................................... (name of process) which moves k)................................................ around the plant to wherever it is needed. The cells are l)..................................... (dead or living) and the transport is m).........................................(active/passive) requiring the plant to n)......................................................... in order to make the process happen. Page 30
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Worksheet 10 keep it simple science Test Questions Multiple Choice ®
1. A blood vessel with relatively thin muscle layer and equipped with one-way valves is most likely a: A. Vein B. Arteriole C. Artery D. Capillary 2. As blood flows through a capillary in an active muscle, you would expect changes in the substances carried in the blood, as follows: A. B. C. D.
Increase in CO2, decrease in O2 and sugars. Decrease in CO2 and sugars, increase in O2 Inrease in CO2 and sugars, decrease in O2 Decrease in CO2 and O2, decrease in sugars
3. Which line correctly identifies the way in which most of the oxygen and carbon dioxide gases are carried in the blood? Oxygen A. dissolved in plasma, B. in haemoglobin, C. in white cells, D. in haemoglobin,
Carbon Dioxide in haemoglobin dissolved bicarbonate ion in haemoglobin dissolved carbonic acid
4. The “Oximeter” is able to measure percentage oxygen saturation of the blood because, depending on the amount of oxygen present: A. B. C. D.
the blood pH changes the ratio of red and white cells changes the blood flows at a different rate haemoglobin absorbs light differently
5. Which statement about plant transport systems is correct?
section 3
Name....................................
Longer Response Questions 6. (5 marks) Describe the structural difference(s) of veins and arteries, and relate these differences to the functions of these blood vessels.
INSPECTION COPY for schools only 7. (9 marks) a) Contrast the way(s) that the gases oxygen and carbon dioxide are carried in the blood.
b) These gases are described as the “respiratory gases” because of their involvement in cellular respiration. Summarise this process with a chemical equation.
c) How is the release of oxygen from the bloodstream facilitated by the high concentration of carbon dioxide in the body tissues?
8. (4 marks) Identify 2 of the “blood products” extracted from donate blood, and describe the uses of these products.
9. (6 marks) Construct a table to contrast the processes of Transpiration and Translocation in plants. Your answer should cover: • the name and nature of the vessels involved. • the substance(s) transported. • the basic nature of the processes.
A. Xylem use active transport for Transpiration. B. Xylem cells are alive and do Translocation. C. Phloem uses active transport to move nutrients. D. Phloem tubes carry out Transpiration by passive means.
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Worksheet 11 Excretion & Water Balance
Fill in the blanks. Water is vital to all living things because: 1. It is the a)......................... of life, and most substances in a cell are b).................. in water. 2. Water is involved in many c)........................ reactions, such as photosynthesis or d)................................ 3. Water has very high “heat e)......................................” and “heat of f)....................................” so it is vital to temperature control. 4. Water g)............................ and cushions cells and organs. For example, plants rely on water in cell h)........................... to keep leaves and stems upright.
Name....................................
Maintaining the correct balance of both water and dissolved i).......................... is another aspect of j)................................... In vertebrate animals, the control of water balance is done by the k)..........................., which also are responsible for excretion of l)............................. wastes. Different animals produce different wastes: the fish produce mainly m)........................... while birds and insects produce n)........................... and mammals produce o)......................... In fish, the kidneys are used mainly for p)........................ because excretion of the ammonia takes place from their q)................................
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Worksheet 12 Water Balance in Plants & Animals
Name....................................
Fill in the blanks Insects process their nitrogenous wastes into the chemical a)......................................... which has very low solubility. This allows them to excrete “urine” which is almost entirely b)...........................
A good example is the way that estuarine animals can maintain j)...................................... balance despite the fluctuations in salt concentrations as the k)......................... change.
Many Australian mammals excrete very c)........................ (small/large) amounts of d)....................... (dilute/concentrated) urine. They achieve this by having increased ability to reabsorb e)............................... from the nephron tubules, and can f)................................. (actively/passively) pump urea from g)............................. into the h)...................................
Mangrove plants deal with salt by special root tissue to l).............................. its entry, or by m).................................. salt onto their leaves, or by n).......................... salt in older leaves which are later shed.
When an organism can maintain homeostasis despite significant variations in the environment, this is called i).......................................... Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Many Australian plants are well-adapted to conserve water by such features as leaves which are o)...................................... (shape & size) and are covered with a thick, waxy p)........................... They often have fewer q)......................... on their leaves, or may be covered with r)..................... to trap a layer of air. Page 32
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Worksheet 13 Kidney Function
Fill in the blanks. Each kidney contains about 1 million units called a)............................ There is a coiled blood vessel, the b)....................................... which is inside the c).............................. capsule. Here the process of d)............................ takes place, where water and many dissolved substances leave the blood and flow throught the e).......................................... The second process is f).............................. in which any useful substances (most of the water, plus g)....................... and ...........................) are absorbed back into the h)........................... by a combination of active transport and i)................................. Some water plus the j).................... are not reabsorbed but pass into a k)................................. duct, and down the l).......................... to the bladder to await excretion. The kidneys also have a role in m)...................................... by adjusting the amounts of water and n).............................. that are reabsorbed into the blood. This function is controlled by the o)..................................... which monitors “water balance” and controls the release of the hormone p).......................... from the q)................................... gland. This hormone increases the permeability of membranes in the r)............................... so that s)............... (more/less) water will be absorbed, and t)............................. (more/less) urine formed. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Name....................................
So, an increase in ADH secretion leads to greater u)........................................... (excretion/retention) of water, while a decrease in ADH results in v)................................ (more/less) urine production. Another hormone called w).......................................... is produced by the x).......................................... glands controls the reabsorption of y).................................. Some people do not produce enough of this hormone and so have a chronic salt-balance problem called z)................................. Disease. This disease is treated by aa)......................................... Therapy (HRT). If a person’s kidneys fail, they can have their blood “cleaned” of wastes by the process of “Renal ab)................................... This is similar to kidney function in that both involve movement of dissolved chemicals through ac)................................. membranes. It is different from kidney function in that it involves only ad)............ (number) process, which involves ae)...................................... (active/passive) diffusion. Kidney function has af)............................ (number) steps, and involves both ag)....................................... (active/passive) transport and osmosis.
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Worksheet 14 Test Questions
Multiple Choice 1. A freshwater fish: A. B. C. D.
produces a large volume of dilute urine. produces a small volume of concentrated urine. excretes urea in large amounts via the kidneys. excretes water from its gills and must drink to replace it.
2. In the mammalian kidney nephrons the formation of urine occurs in 2 stages. Which line describes correctly the location of each process? A. B. C. D.
Filtration Glomerulus Renal tubules Glomerulus Bowman’s capsule
Reabsorption Bowman’s capsule Ureter Renal tubules Collecting duct
Name....................................
section 4 6. (4 marks) Outline the processes of Filtration and Reabsorption in the nephron of a mammalian kidney. Identify where each process occurs and the main events occurring.
7. (6 marks) Compare and contrast the role of the hormones “ADH” and “Aldosterone” in the maintenence of mammal homeostasis. Your answer should include • source of each hormone • precise effect on the target organ • how this contributes to Homeostasis
3. An increase in the level of the hormone “ADH” would cause the kidney nephrons to: A. B. C. D.
reabsorb reabsorb reabsorb reabsorb
less salt. more water. more salt. less water.
8. (5 marks) a) Outline the process of excretion of nitrogenous wastes in insects, explaining how it contributes to conservation of water in their bodies.
4. Insects conserve water by excreting their nitrogenous wastes in the form of: A. a semi-solid paste of uric acid. B. a small volume of urine, highly concentrated in urea. C. a large amount of ammonia-containing urine. D. pellets of solid urea.
b) Using a named example of an Australian mammal, explain how the excretion of nitrogenous wastes is achieved with minimum water loss.
Longer Response Questions Use reverse if insufficient space. 5. (4 marks) Discuss briefly the importance of water in living organisms, identifying 4 functions of water.
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9. (8 marks) a) What is “Enantiostasis”? Give an example of an environment where this process is vital and outline some of the strategies for achieving enantiostasis in the named environment. b) Identify strategies for conservating water in 2 named Australian plants.
c) Describe 2 strategies used by mangrove trees to maintain water balance in a saline environment.
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Answer Section
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Worksheet 3
2.a) reaction rate (=activity) increases as temp. goes up because molecules are more likely to collide and react with each other.
Temp
2. B
3. D
4. A
5. C
6. D
7. a) Enzymes are protein molecules and each has a a particular 3-dimensional shape which fits its substrate like a key fits a lock. Usually each enzyme will only “fit” one particular substrate, so it will only catalyse one reaction. b) Any change in temperature or pH can change the shape of an enzyme, by causing the protein chain to alter the way it is folded and twisted. As its shape changes, its ability to “fit” the substrate will change too. Thus each enzyme only works fully within relatively narrow ranges of temperature and pH. 8. a) Table should be ruled and have clear headings. The values in the 3rd column should be: -1 Reaction Rate (min ) Reaction Rate v Temp. Graph 0.25 0.5 1.0 5.0 0.4 0.1 5
1. graph
Activity
Worksheet 2
1. B
4
a) metabolism b) speeds up c) used up / consumed d)enzymes e) protein f) amino acids g) 3-dimensional shape h) substrate(s) i) specific j) & k) temperature & pH l) shape m) & n) acidity & alkalinity o) 7 p) below q) above 7 r) 7 / neutral s) stomach t) acidic u) stable / at the same level v) temperature w) pH x) water y) blood sugar z) negative aa) receptor ab) control centre ac) effectors ad) nervous ae) hypothalamus af) brain
Reaction Rate (1/min)
Worksheet 1
3. graph
c) No. 0 5 10 15 20 25 30 The graph shows o that at human Temperature ( C) body temp. (37C) the enzyme’s activity is almost zero. This enzyme would NOT function in a human body.
4. At the optimum pH the shape of the enzyme is a perfect “lock & key” shape to fit the substrate, so activity is at a maximum.
pH
5. At pH’s either side of optimum the shape of the enzyme changes so that the “fit” with the substrate is no longer perfect, so activity declines.
Activity
6. graph 7. a) As the concentration of substrate molecules increases, it becomes more likely that they will Substrate concentration collide with an enzyme and undergo the reaction. So reaction rate increases. b) However, once all the available enzyme molecules are being used, (they are “saturated” with substrate) increasing the concentration cannot increase reaction rate any further, so the graph levels off.
Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
2 1
b) graph
3
(These values are calulated as 1/time taken)
Activity
b) Above the optimum the shape of the enzyme protein begins to change and be distorted. The substrate(s) no longer fit the enzyme perfectly, and activity declines rapidly.
9. a) Homeostasis is the process of maintaining a stable, internal environment, for such things as temperature, pH, water balance, etc. b) Homeostasis is vital so that the optimum conditions (of temp., pH etc) for enzymes to function efficiently are maintained. Efficient enzyme activity is essential so that the reactions of metabolism occur at a rate appropriate for life functions. c) example: thermostat control of an oven A temperature sensor constantly monitors the temp. If oven is too cool, the control mechanism sends an electrical signal to turn the heating element on. (effector) If the oven is too hot, a signal is sent to turn the heating element off, so the oven will cool down. By always taking action in the opposite direction (negative feedback) a relatively stable temperature is maintained. Page 35
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Worksheet 4
®
keep it simple science a) hypothalamus b) effector c) dilation d) more e) sweat f) perspiration g) evaporates h) hormones i) thyroid j) constricted k) the skin l) raised / erected m) insulate n) shiver o) ectotherms p) reptiles q) Sun r) Blue-tongue lizard s) sunbakes t) seeks shade u) copperhead snake / corroboree frog v) becoming dormant w) endotherms x) & y) mammals & birds z) feathers aa) blubber (fat) ab) ears ac) lose water ad) fore arms ae) insulation af) shunted back into the body ag) deciduous ah) shed their leaves ai) stomates aj) needle / spine ak) light al) sclerophyll am) narrow an) droop downwards
Worksheet 5 1. A
2. B
3. D
4. C
5. C
6. a) The hypothalamus is both the receptor and control centre for regulation of temperature. Blood flowing through the hypothalamus is constantly monitored by heat-sensitive cells. If body temperature is even slightly high or low, the hypothalamus sends nerve messages to various effector organs to either warm or cool the body back to its correct temperature.
7. c) Desert-living endotherms, such as the Bilby, cannot afford the water loss involved with sweating to cool off. Instead, they have large ears to radiate heat away. They seek shade in the heat of the day and are active only in the evenings and early morning. Instead of sweating, they “pant” so that evaporation from the mouth and throat has a cooling effect. 8. Sclerophyll plants have • small, narrow leaves to reduce surface area exposed to Sun. • shiny leaf cuticle to reflect some radiant heat • leaves which “droop” downwards. This allows for absorption of light for photosynthesis in the cool of the morning, but avoids heat absorption in the heat of midday.
Worksheet 6 a) plasma b) red c) haemoglobin d) oxygen e) bicarbonate f) water g) carbonic h) plasma i) sugars j) amino acids k) urea l) protein m) arteries n) pressure o) heart p) Veins q) valves r) flowing backwards s) one cell t) tissues u) digested nutrients v) liver w) processing & storage x) urea y) kidneys z) water & salts aa) oxygen ab) carbon dioxide ac) blood ad) cells ae) oxygen af) carbon dioxide
b) Veins and arteries can be constricted (narrowed) to reduce the blood flow to the skin. This reduces the amount of heat lost through the skin, thereby helping to warm the body. The opposite process of dilating (widening) the blood vessels allows more blood flow to the skin. This allows more heat to be lost from the skin, thereby cooling the body.
Worksheet 7
c) Three other effector organs: Sweat glands (perspiration), skeletal muscles (shivering), thyroid gland (hormone thyroxine), body hair muscles (goose bumps).
2. CO2 is mostly carried as bicarbonate ion.
7. a) Endotherms are animals which generate their own body heat. Ectotherms rely on their environment to supply their body heat; they do not generate internal body heat. b) Ectotherms such are the Blue-Tongue Lizard often use instinctive behaviours to regulate temperature. When too cold, it will sunbake, flattening its body to increase the surface area exposed to the Sun. When too hot, it will seek shade and avoid the heat of the Sun. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
1. CO2 reacts with water to form carbonic acid CO2 + H2O H2CO3 Carbonic is a weak acid which partly ionises H2CO3 H+ + HCO3-
3. The equations show that carbon dioxide reacts with water forming an acid. If allowed to accumulate, this would lower the pH, which could seriously affect the activity of enzymes and disrupt metabolism. 4. As shown in the equations above, the presence of carbon dioxide lowers the pH. In tissue capillaries, the slightly lowered pH alters the shape of the haemoglobin molecules slightly. This causes them to release the oxygen molecules they are carrying, which then diffuse into the cells.
INSPECTION COPY for schools only Page 36
Inspection Copy for Schools only.
KISS Resources for the NSW Syllabus.
Worksheet 8
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9.
keep it simple science a) red b) iron c) haemoglobin d) 4 e) oxyhaemoglobin f) carbon dioxide g) release h) diffuse i) percent oxygen saturation j) 95% k) Oximeter l) red light & infra-red light m) absorbed n) Red o) immunity p) Platelet q) Plasma r) blood volume s) stored t) immune-responses u) diseases v) Haemoglobin w) Oxygen x) Perfluorocarbons
Worksheet 9 a) xylem c) leaves e) passive g) evaporates i) phloem k) nutrients / sugars m) active
b) roots d) dead f) transpiration h) cohesive j) translocation l) alive n) use energy
Transpiration Vessels involved
Xylem (dead cells)
Substances transported
Water & minerals
Processes involved
Passive transport
2. A
3. B
4. D
5. C
6. Arteries have thick, muscular walls. This allows them to withstand the high pressure blood they carry as the heart pumps. Being elastic, the walls can expand outwards under pressure, then contract and help squeeze the blood on its way. Veins have thinner walls since the blood they carry back to the heart is at low pressure. Veins are equipped with valves to prevent back-flow. The thin walls of a vein allow them to be compressed by neighbouring muscles, which helps squeeze the blood forward. 7. a) Oxygen is carried attached to the haemoglobin molecules in the red blood cells. Most carbon dioxide is carried in solution in the blood plasma as bicarbonate ion, HCO3-. b) C6H12O6 + 6O2
6CO2 + 6H2O + ATP
c) The high concentration of dissolved CO2 causes the pH to be slightly lower (because CO2 reacts with water forming carbonic acid). This change in pH causes a change in the shape of the haemoglobin molecule, which causes it to release oxygen, which can then diffuse into the surrounding body cells. 8. Red Cell Concentrate contains about 2x as many red cells as normal blood. It is used to treat people with severe anaemia, or following severe blood loss. Platelet Concentrate is given to patients who need extra blood-clotting capability, such as leukemia sufferers. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
Phloem (living cells) Nutrients, especially sugars Active transport
Worksheet 11 a) solvent c) chemical e) capacity g) supports i) salts k) kidneys m) ammonia o) urea q) gills
b) dissolved d) metabolic / chemical f) vaporisation h) vacuoles j) homeostasis l) nitrogenous n) uric acid p) water balance
Worksheet 10 1. A
Translocation
Worksheet 12
INSPECTION COPY for schools only
a) uric acid b) solid / dry c) small d) concentrated e) water f) actively g) blood h) tubules / urine i) enantiostasis j) water & salt k) tides l) limit m) secreting / excreting n) storing / accumulating o) small & narrow p) cuticle q) stomates r) hairs
Worksheet 13 a) nephrons b) glomerulus c) Bowman’s d) filtration e) renal tubules f) reabsorption g) sugars / salts / amino acids h) bloodstream i) osmosis j) urea k) collecting l) ureter m) homeostasis n) salt o) hypothalamus p) ADH q) pituitary r) renal tubules s) more t) less u) retention v) more w) aldosterone x) adrenal y) salt z) Addison’s aa) Hormone Replacement ab) Dialysis ac) semi-permeable ad) one ae) passive af) two ag) active
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Inspection Copy for Schools only.
KISS Resources for the NSW Syllabus.
Worksheet 14
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keep it simple science 1. A
2. C
3. B
4. A
5. Water is the solvent of life All the chemical reactions of metabolism take place in water solution, and the transport of materials takes place in water solution. Water is involved in life chemistry Water is a reactant or product of many metabolic reactions. Water is vital in temperature regulation Water has a very high specific heat capacity. This helps stabilize the temperature of all living things. Evaporation of sweat is an important cooling mechanism in mammals. Water supports and cushions cells and organs Water solutions in the tissues helps to cushion organs against bumps and impacts. (eg cerebrospinal fluid around the brain) 6. Filtration occurs in the glomerulus. Some of the water of the blood plasma and its dissolved sugars, minerals, urea etc seep out of the blood vessel, like water through a filter paper. Blood cells and proteins cannot leak out. This “filtrate” flows along the renal tubules where reabsorption occurs. Useful nutients (sugars, amino acids) are actively transported back into the bloodstream. Most of the water in the filtrate flows back to the blood by osmosis. A portion of the water with dissolved urea flows on to be excreted as urine. 7. ADH is secreted by the pituitary gland (under control of the hypothalamus) It alters the permeability of the renal tubules to water. Increased ADH allows greater water reabsorption, and less urine production. Aldosterone is secreted by the adrenal glands. It stimulates the cells lining the renal tubules to actively transport more sodium ions back into the blood from the renal fitrate. This retains more salt in the body to adjust “osmotic balance”.
8. b) The Spinifex Hopping Mouse is a desert-dweller which produces very small amounts of very concentrated urine. This is achieved because: • the nephron tubules are very long, allowing for more reabsorption of water, and less volume of urine. • the cells lining the tubules are able to actively transport urea from the blood into the urine. This allows the urine to be even more highly concentrated than in other mammals. 9. a) Enantiostasis is a special case of homeostasis, in which an organism maintains a stable internal environment despite significant changes in the environment around it. An example of a habitat where this is important is a tidal estuary, where the tides cause the salinity of the environment to fluctuate. To maintain their “osmotic balance” while their evironment changes from virtual fresh water, to salty and back again, requires estuarine organisms to cope by strategies such as: • burrowing into the mud where the salinity is more constant. (eg crabs & yabbies) • adjusting the functioning of their kidneys from water excreters to water conservers as the tides change. (eg fish) b) Spinifex Grass has fine hairs all over its leaves. This traps a layer of still air near the leaf, reducing the evaporative effect of the wind. Gum trees, such as the River Red Gum, has leaves with very few stomates, and a thick, waxy cuticle to minimize water losses. c) Mangroves: • secrete salty brine onto the leaf surface. This washes away when it rains. • accumulate salt in older leaves which are then shed, carrying away a load of excess salt.
INSPECTION COPY for schools only
8. a) The insect equivalent of kidneys are the “malphigian tubes” which run all though the body and collect and concentrate nitrogenous wastes in the form of uric acid. Since this is basically insoluble, the “urine” can be concentrated to a semi-solid paste by reabsorbing virtually all the water, before passing the wastes into the rectum for excretion with the digestive wastes. This means there is virually no loss of water during excretion. Biology 9.2 “Maintaining a Balance” PhotoMaster copyright © 2014 KEEP IT SIMPLE SCIENCE www.keepitsimplescience.com.au
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Inspection Copy for Schools only.
