COURSE READINESS ASSESSMENT FOR
PHYSIOLOGY
MACROMOLECULES
What are Macromolecules? Macromolecules are very large molecules important to living organisms. Most macromolecules are built by joining smaller molecule subunits, often called “monomers”.
Types of Macromolecules There are 4 classes of macromolecules: Carbohydrates Lipids Proteins Nucleic Acids Let’s look at each of these individually.
Carbohydrates Carbohydrates may be used for energy storage or for structure. Carbohydrates come in different sizes. Large carbohydrates (polysaccharides) are long chains of smaller carbohydrates (monosaccharides).
Carbohydrates Made mostly of carbon, hydrogen and oxygen Small carbohydrates are called monosaccharides,
single or simple sugars.
Most common monosaccharide is glucose: C6H12O6 In cells, glucose looks like:
C6 C5
C4
C1 C3
C2
Other common monosaccharides:
Ribose, deoxyribose, fructose, galactose
The Condensation or Dehydration Reaction Monosaccharides are joined to form polysaccharides by
removing water, creating a covalent bond between them.
+ + H2O This is a common link between C1 of a glucose molecule and C4 of a second glucose.
Disaccharides Consist
of two monosaccharides joined by a dehydration reaction, creating a covalent bond between them.
sucrose (glucose + fructose)
lactose (galactose +
© Don A. Carlson/ Wikimedia Commons / CC-BY-SA-3.0 / GFDL
glucose)
Storage Polysaccharides: Starch 1.
Many glucose molecules connected C1 to C4 with C6 always sticking up (“α” orientation) will make the plant starch amylose:
1.
Sometimes there will be a branch point made by attaching glucoses C1 to C6, like amylopectin (another plant starch):
Plants use the carbohydrate starch for long-term energy storage, often in seeds such as wheat, corn or rice, or in tubers such as potatoes.
Storage Polysaccharides: Glycogen Animals will make long chains of glucose similar to
plant starch, but with more branching
The resulting polysaccharide is called glycogen
Animals use glycogen as short-term energy storage, stockpiling it in the liver and muscles.
Structural Polysaccharides: Cellulose Plants cells can make chains of “β” glucose molecules to form
cellulose
The glucose molecules in the chain are arranged so that they
alternate their orientation, as shown above. This gives cellulose a very straight structure.
Plant cell walls are composed of cellulose. Animals cannot break down cellulose (we call it fiber) and depend upon microbes to do this.
Structural Polysaccharides: Chitin Glucose may be modified by adding a nitrogen-containing group
to C2
Chitin is the polysaccharide made by joining many of these
modified glucose molecules
Chitin is in the exoskeletons of insects, spiders, crabs and other animals. Chitin is also found in fungi, such as mushrooms. Surgical thread made of chitin dissolves over time.
Summary of Carbohydrates Smallest carbohydrates are called monosaccharides.
Glucose is a common monosaccharide. Polysaccharides are made by joining many monosaccharides, forming covalent bonds between them by condensation or dehydration reactions Storage Polysaccharides Starch in plants Glycogen in animals
Structural Polysaccharides Cellulose in plants Chitin in animals & fungi
Lipids Lipids are a diverse group of macromolecules. Most lipids are hydrophobic (“water hating”).
Types of Lipids There are many types of lipids We will focus on 3 important lipids: Fats (also known as triacylglycerols or triglycerides) Phospholipids Steroids
Fats Consist of: Glycerol, a 3-carbon molecule H H-C-OH H-C-OH H-C-OH H
3 fatty acids, each 8 – 22 carbons long CH3CH2CH2CH2CH2CH2…COO- A SATURATED FATTY ACID CH3CH2CH=CHCH2CH2…COO- AN UNSATURATED FATTY ACID
Saturated Fatty Acids Saturated fatty acids Contain only single covalent bonds between carbons Simplified structure can be shown as: Fats with saturated fatty acids are solid at room
temperature. Examples: Butter, lard, margarine, animal fat Saturated fats can collect in the blood vessels and cause heart disease.
Unsaturated Fatty Acids Contain at least 1 double covalent bond Cis unsaturated fatty acids Double covalent bonds make kinks in fatty acid: Liquid at room temperature (Example: Cooking oil) Cause fewer heart problems Trans unsaturated fatty acids Double covalent bonds present, but arranged without kinks: Solid at room temperature, like saturated fats Cause heart problems like saturated fats
Fat structure The 3 fatty acids are attached to glycerol using
condensation reactions. An example of a fat with two unsaturated fatty acids: -C-O-C-C-O-C-C-O-C-
Fats are used for long-term energy storage in plants and animals.
Phospholipids Consist of: Glycerol A phosphate group Water-loving “head” A nitrogen-containing group 2 fatty acids Water-hating “tails” Hydrophobic or water-hating tails Hydrophilic or water-loving head
Phospholipids Make Membranes Membranes of all cells consist of a double layer of
phospholipids, called a phospholipid “bilayer”
Hydrophilic heads are pointed away from each other Tails form hydrophobic core
Phospholipids make strong, flexible membranes like those around the yolk of an egg.
Steroids Steroids are a class of lipids that include Cholesterol Sex hormones, such as testosterone and estrogen They have a common structure of 4 interconnected
rings, as seen in cholesterol:
cholesterol
Functions of Steroids Cholesterol maintains the flexibility of a cell membrane We make cholesterol in our livers and eat it in our food. Steroid hormones direct our cells to do specialized tasks. Sex hormones affect the growth and function of reproductive organs Cortisone is active in carbohydrate metabolism and is used to treat allergic reactions.
Summary of Lipids Fats, made of glycerol and 3 fatty acids, are used for
long-term energy storage. Saturated and trans fats are unhealthy.
Phospholipids have a hydrophilic head and 2
hydrophobic tails. Cell membranes consist of a bilayer of phospholipids.
Steroids consist of 4 interconnected rings. Cholesterol
and the sex hormones are examples of steroids.
Proteins Proteins are macromolecules consisting of long chains of subunits called amino acids. They do a number of jobs in organisms, including acting as enzymes, hormones, membrane channels, and receptors.
Amino Acids There are 20 possible amino acids Have amino (-NH2) and carboxyl (-COOH) group
connected to a central (“α”) carbon Different amino acids have different “R” groups (also called side groups or side chains) attached to the α carbon R groups may be nonpolar, polar, acidic or basic Amino Group
H H
H N C C R
R group
O OH
Carboxyl Group
Making Polypeptides Amino acids are joined by condensation (dehydration)
reactions
Joins the amino group of an amino acid to carboxyl group of
another amino acid The covalent bond that is formed is called a peptide bond As with all condensation reactions, water is removed H H
H N C C R
O OH
H
+
H
H N C C R
O OH
H H
H N C C R
O H
H N C C
peptide bond
R
O OH
Levels of Protein Structure I Primary (1o) structure Sequence of amino acids Determined by gene DNA Held together by covalent (peptide) bonds Secondary (2o) structure Folding of regions of polypeptide May be α helix or β pleated sheet Held together by hydrogen bonds
Levels of Protein Structure II Tertiary (3o) structure Folding of the entire protein into a characteristic shape May be globular (enzymes) or fibrous (hair proteins) May be held together by covalent, ionic, hydrogen bonds (and sometimes other possible ones) Quaternary (4o) structure Association of 2 or more proteins Example: Hemoglobin, the oxygen-carrying protein in blood, consists of a complex of four globin proteins
Denaturing a protein A protein is denatured when the bonds holding its shape are
broken
When a protein is fully denatured, only its primary structure remains Since shape is critical for proteins, denaturing has a negative effect
on protein function
Many environmental factors can denature a protein. Examples: High
temperatures, very acidic or basic pH, high salt concentrations.
Summary of Proteins Subunits are amino acids Amino acids are joined by condensation reactions that form peptide
bonds
The amino acid sequence is a protein’s primary structure. The primary
structure can also be called a polypeptide.
Local folding of a polypeptide is a protein’s secondary structure Tertiary structure is the additional folding of the protein into its
characteristic shape
The quartenary structure is the association of two or more proteins
Nucleic Acids Nucleic acids are macromolecules that store and transmit inherited information. DNA and RNA are two types of nucleic acids. DNA and RNA are long chains of subunits called nucleotides.
Nucleotides A nucleotide consists of: A monosaccharide
DNA nucleotides: Deoxyribose RNA nucleotides: Ribose
At least one phosphate group A nitrogenous base, a ring structure that contains nitrogen
The pyrimidines are have only 1 ring Cytosine and Thymine are pyrimidines In RNA, Uracil is in place of Thymine The purines have 2 rings Adenine and Guanine are purines
A forms 2 hydrogen bonds with T
G forms 3 hydrogen bonds with C
A = T (In RNA, A bonds with U) G=C
Backbone of DNA and RNA Nucleotides are joined so that the backbone consists of alternating
phosphate groups
and monosaccharides
Nucleotide strands have ends: 5’ and 3’ (’ = “prime”) DNA is double stranded, RNA is single stranded 5’ end
3’ end
DNA is a Double Stranded Helix 5’ end
3’ end
T
G
3’ end
Note that the 2 nucleotide strands in DNA are oriented in opposite directions.
A
C
This is called an antiparallel arrangement.
C
G
• A forms 2 hydrogen bonds with T
G forms 3 hydrogen bonds with C
5’ end
A=T G=C
DNA Locations and Functions DNA is located In the cytosol of bacteria In the nucleus of the cells of eukaryotes, such as humans Some DNA functions Act as genes: Stored information to make proteins Is passed from one generation to the next
RNA Structure RNA nucleotides contain Ribose instead of deoxyribose Uracil instead of Thymine
5’ end
RNA is Single stranded instead of double stranded Smaller than DNA 3’ end
Summary of Nucleic Acids Nucleic acids are macromolecules used as
information storage and can be passed from one generation to the next. DNA and RNA are the two major types of nucleic acids.
Nucleotides are the subunits of DNA and RNA DNA is a double stranded molecule RNA is a single stranded molecule