Lesson Plan: Teaching Photosynthesis and Cellular Respiration in Tandem Timeline: 2+ class periods MO Content Standards: Strand 3: Characteristics and Interactions of Living Organisms 2. Living organisms carry out life processes in order to survive B. Photosynthesis and cellular respiration are complementary processes necessary to the survival of most organisms on Earth a. Explain the interrelationship between the processes of photosynthesis and cellular respiration (e.g., recycling of oxygen and carbon dioxide), comparing and contrasting photosynthesis and cellular respiration reactions b. Determine what factors affect the processes of photosynthesis and cellular respiration (i.e., light intensity, availability of reactants, temperature) D. Cells carry out chemical transformations that use energy for the synthesis or breakdown of organic compounds a. Summarize how energy transfer occurs during photosynthesis and cellular respiration as energy is stored in and released from the bonds of chemical compounds (i.e. ATP)

Overarching Enduring Understanding: • A direct relationship exists between structure and function in living systems. Enduring Understanding: • Photosynthesis and cellular respiration are complementary processes necessary to the survival of most organisms on Earth. Essential Question: • How do cells transform, store, and use energy to maintain the survival of organisms? Lesson Description: A primary goal of these two lessons is to introduce students to the ideas behind these two processes. In most cases, I would follow up with hands on labs and/or activities to further the development of these two processes. I would also assign textbook readings to complement the lessons we were doing in class.

Day 1: Introduce the concept with the Cell Energy lesson (see below). The point of this exercise is to uncover prior knowledge find out (as the teacher) where student understanding is at this point. This information will not only be helpful for this two-day lesson, but also helpful in deciding what to do after these two days. For instance, if you discover students really have trouble understanding CO2 has mass, a short demo or lab on gas properties may be appropriate. After the class discussion of the first question, students go online to learn about a few basic ideas. For this, find a few good websites you find suitable for your students’ ability levels. Use websites with introductory information and use a website like www.portaportal.com to host the links. This site is easy to set up and easy for students to use. Students should be able to work in pairs and find the answers to many of the questions before the end of the hour. Part three of the first day is handing out the word sort cards marked “A”. Students should work in pairs and try to make some sense of the words and what they mean. As they sort their words into groups, circulate and ask lots of probing questions. Encourage them to sort them any way they see fit. Lastly, have them record the pattern they sorted their words into in the box on their paper. Collect the cards and the student’s Cell Energy handouts. Day 2: Return their papers and “A” cards. Have them reassemble their cards into their original pattern. Next, handout the “Photosynthesis and Respiration: How Cells Make and Use Energy” reading and the second set of cards marked “B”. This time, students should use their reading and try to build a concept map using both sets of cards. They may choose to use their original layout or go with another plan. After this, students can move to a larger piece of paper to build a concept map or use computer software (such as Inspiration or SMART Ideas) to build their final map. On Day 3, students can share their maps and compare differences and similarities as you sort out the events taking place in both processes. Day 3 and Beyond – Follow Up: Based on student understanding of the concepts and time available, students could perform a photosynthesis lab (floating disks or elodea) and/or respiration labs (human respiration). Most labs suitable for high school measure O2 or CO2 production (depending on which process). However, these sorts of labs depend upon or improve upon students being able to understand the concepts of photosynthesis/respiration themselves. Doing labs in absence of a concept development activity (like the lesson described here) or doing the concept development activity without a lab lessens the chance students will actually understand the ideas. In the interest of time and materials, there are several other ways to visualize these processes. Students can build models or use computer software simulations. Logal software company created an excellent series called “Explorer” that offered computer simulations in which students could manipulate and control different variables that affected the rate of photosynthesis. The company sold their product to Riverdeep software who in turn made the software web-based. There are many other animations and/or simulations on the web that can assist students with these concepts.

Personal Reflections on Lesson Design: (1) What I learned as I designed this lesson: In designing this lesson, I attempted to recall my own experiences with learning photosynthesis and respiration. I remembered really struggling with the terminology and details involved in the processes. I remembered being taught the two reactions as reciprocal in nature. While reflecting on the experiences of my students during the last 15 years, I can honestly say some students “learned” both reactions, but still had no recollection of “what goes in” and “what goes out.” In preparing for the development of this activity, I modified many of the text resources my students already had access to. I was very selective in the amount of information I wanted to expose them to. I also reviewed in my own mind the relationships between photosynthesis and respiration. Making concept maps really helped me with this. This translated into taking the word sort idea into a concept mapping exercise. My goal is for the students to focus on the big ideas and not get lost in the details. I’m very excited to try this out! (2) How used to teach this lesson before: While teaching this content before, I remember students struggling with the details. In the past, I usually presented students with the content via notes and video animations. Students memorized the reactions as I taught them separately. I have always taught photosynthesis first because it has only two reactions (light reaction and Calvin cycle). Since photosynthesis is also the metabolic driving force for most producers (something students will already have learned in ecology) it only seems fitting that cellular respiration follows after photosynthesis is presented. Also, cellular respiration actually has three reactions (glycolysis, Kreb’s cycle, and the electron transport chain). I’ve done some lab activities in the past with limited success. Again, it seems most labs mainly focus on assessing the presence or absence of CO2 or O2 (depending on which process we are demonstrating). While I think the labs are great learning experiences, it’s really easy for students to collect data, analyze results and still walk away with a limited understanding of metabolism and the relationships between photosynthesis and cellular respiration. I’m still searching for good framing and synthesizing activities to help students develop and mentally assess their conceptualization of the ideas we are studying. Like a proverbial “mental container” that I provide to students. As they learn material through readings, visuals, lab experiences, and discussions, they “fill” their containers. In the end however, they need to be able to access these containers and build new knowledge and/or self-assess their own understanding. This notion is what inspired me to try this new design and attempt to teach both metabolic processes in tandem. Ultimately, my goal is for deeper understanding of the principles and generalizations surrounding cellular metabolism (photosynthesis, cellular respiration, and fermentation).

Cell Energy!

Due Date:

Enduring Understanding: Cells use distinct and separate structures to perform chemical processes essential towards maintaining homeostasis.

Essential Question: How do cells transform, store, and use energy to maintain the survival of organisms?

Assessing Prior Knowledge:

From Seed to Tree ?

Answer the questions in your own words individually. Afterwards, discuss your answers with members at your tables. 1. Estimate how much you think a seed weighs.

2. Estimate how much you think a full-sized tree weighs.

3. Estimate the difference in mass between a seed and a tree.

4. Where do you think the mass of the tree comes from?

Procedure: Using your computer, visit some websites to learn more about how cells make and use energy. Be sure to answer the following questions as you explore these concepts. Use the following site to find the recommended list of URLs for this activity:

www.portaportal.com sign in as guest with: ______________________ A. How do plants and animals obtain energy?

B. In what organelle does the process of Photosynthesis occur?

C. In what organelle does the process of Respiration occur?

D. In what type of cells do Photosynthesis and Respiration take place? For each process describe if it is: Plant, Animal, Both, Neither

E. Why are animal cells not capable of carrying out Photosynthesis?

F. Photosynthesis and Respiration can be summarized into equations. Write the equations and how do they relate to one another.

G. Analyze why leaves change color in autumn.

H. Identify the parts of the plant involved in Photosynthesis.

I. Describe how glucose is broken down during Respiration.

J. Name 3 interesting facts you learned from the websites:

Concept Assessment: 1. 2. 3. 4. 5.

Your teacher will give you a stack of words. Lay all the words out on your table and sort them out. Talk with a partner at your table and try to look for patterns. Look for general and specific words. Finally, once you think you have the words arranged in a way that sums up what you understand so far about cell energy, record the way you arranged the words on the next page. 6. Give the word cards back to your teacher at the end of the class.

Results from Cell Energy Word Sort:

Photosynthesis and Respiration: How cells make and use energy In order for cells to do any work, they need energy! Where does this energy come from? How do they store it? How do they use it? The answers to these questions and more are found in the complementary processes of photosynthesis and respiration. In photosynthesis, energy is stored in chemical bonds, while in respiration, those same chemical bonds are broken and energy is released for use by the cell. Before going into the details of photosynthesis and respiration, let’s review a little bit about energy and light and how they are used by cells. Energy Energy can be stored in the form of covalent bonds between atoms. Remember that covalent bonds are bonds created when two atoms share a pair of electrons between them. When these bonds are broken by enzymes, the energy is released for the cell to use. In photosynthesis, plants take energy from the sun and store it in the chemical bonds of glucose, a simple sugar. In respiration, the energy in the glucose bonds is released. The energy released from glucose through respiration is transferred to a molecule called ATP. Think of ATP as a kind of money used by the cell. ATP is used to power some cellular processes, like active transport or enzyme activity, that cost energy. Only plants can photosynthesize, but all organisms carry out some form of cellular respiration because all organisms need to get energy for their cells to use. Key point: All organisms, including plants, use cellular respiration to get energy from the chemical bonds in food. Light Light travels from the sun across 93 million miles of space to get to use here on earth. That’s pretty far, but it only takes 8 minutes for light to travel that distance! A single unit of light is called a photon, and it carries energy. It is the energy of light photons that is harnessed by the plant through photosynthesis.

Photosynthesis The production of glucose in photosynthesis can be summarized by the following equation:

6 CO2

+

12 H2O + light  C6H12O6 + 6 O2 + 6 H2O

carbon dioxide + water + light energy  glucose + oxygen gas + water Let’s break this equation down a little bit. On the left side of the equation, where does the carbon dioxide come from? It is present in the air, and is brought into the plant through tiny pores in the leaf called stomata. How about water, where does it come from? It comes from the soil, and is drawn in by the roots. And, as mentioned above, the light comes from the sun, and provides the energy for the chemical reaction between carbon dioxide and water. On the right side of the equation, notice that photosynthesis gives off oxygen, the very substance we need to breathe. As we will see later, oxygen is a necessary component of cellular respiration. This is why the word ‘respiration’ is used for both breathing and for the release of energy from glucose molecules. Photosynthesis takes place in the chloroplasts of plant cells. In most plant chloroplasts are most abundant in the leaves and give them their green color. Therefore the leaves are the major site of photosynthesis in most plants. Inside the chloroplasts, there are a number of flattened structures that look like stacks of green pancakes. A single “pancake” is called a thylakoid, and the whole stack is called a granum. The chlorophyll pigment, which is very important in photosynthesis, is located in the thylakoid membranes. The rest of the space inside the chloroplast is called the stroma. The process of photosynthesis can be divided into two main parts: the light-dependent reaction and the Calvin cycle. The light-dependent reaction is the energycapture part of photosynthesis, while the Calvin cycle uses that energy to build sugar molecules. In the light-dependent reaction, which takes place in the thylakoid membrane, electrons in a chlorophyll molecule directly absorb the energy in a photon from the sun. These high-energy electrons are carried from the thylakoid to the stroma on special carrier molecules. It is in the

stroma where the glucose-building step of photosynthesis, the Calvin cycle, occurs. In the Calvin cycle, the solar energy in those electrons is used combine carbon dioxide and hydrogen into glucose. The energy that was absorbed from solar photons has now been stored in the stable chemical bonds of a glucose molecule.

to

After glucose is synthesized, it is often processed into sucrose disaccharide) or starch (a polysaccharide) for long-term storage or transport to other parts of the plant.

(a

Respiration How do plants and animals use the energy stored in glucose? Cellular respiration! While only plants can photosynthesize, all organisms perform some kind of respiration. Respiration in eukaryotes is the breakdown of glucose in the presence of oxygen and can be summarized by the following equation:

C6H12O6 + O2

 6 CO2 + 6 H2O + energy

glucose + oxygen  carbon dioxide + water + energy

Notice that oxygen is required for cellular respiration, which is why we breathe it in, and that carbon dioxide is one of the waste products. Notice also that this is the reverse of photosynthesis, where carbon dioxide is taken in and oxygen is a product. In other words, we exist in a beautiful mutualism with plants – they provide us with exactly what we need and vice versa! Respiration consists of three main steps: glycolysis, the Krebs cycle (a.k.a. the citric acid cycle), and oxidative phosphorylation. The end product of these three steps in 36 molecules of ATP, the cell’s energy “money”, per molecule of glucose. Respiration mostly takes place in the mitochondria, but the first step in the breakdown of glucose, glycolysis, actually occurs out in the cytoplasm. In glycolysis, enzymes split a molecule of glucose, which has 6 carbon atoms, into two 3-carbon molecules called pyruvate. A small amount of energy is released in glycolysis, and two molecules of ATP are created. After glucose is split into pyruvate, the pyruvate is transferred to the inside of a mitochondrion, where the Krebs cycle is carried out. In the Krebs cycle, pyruvate is

further broken down by enzymes into carbon dioxide and water and 2 more molecules of ATP are generated. The final step of respiration, oxidative phosphorylation, is where the big payoff in ATP happens. As glucose is broken down in glycolysis and the Krebs cycle, high-energy electrons are transferred to special electron carriers very similar to the ones found photosynthesis. These electrons are passed to electron transport proteins embedded in the internal membrane of the mitochondrion. These proteins are able to use the energy of these protons to make ATP molecules. In this final stage of respiration, 32 molecules of ATP are generated for each molecule of glucose that we started with. The cell now has a big supply of energy money to spend on whatever activities it wants!

Summary: Photosynthesis: light-dependent reaction – energy from sunlight is harvested, water is split into H and O2, occurs in thylakoid membrane Calvin cycle – glucose is created from CO2 and H, energy is stored chemically, occurs in stroma

Respiration: glycolysis – glucose is split into 2 molecules of pyruvate, 2 ATP generated, occurs in cytoplasm Krebs cycle – pyruvate is broken down into CO2, 2 ATP generated, occurs in mitochondria electron transport – electrons transferred to membrane proteins in mitochondria, 32 ATP generated, O2 required

“A” Group Word List • • • • • • • • • •

photosynthesis glucose broken down light energy energy released respiration chloroplast glucose created mitochondrion energy stored carbon dioxide

“B” Group Word List • • • • • • • • • •

stroma oxidative phosphorylation water cytoplasm Krebs cycle glycolysis thylakoids oxygen Calvin cycle light-dependent reaction

glucose broken photosynthesis down

light energy

energy released

respiration

chloroplast

glucose created

mitochondrion

energy stored

carbon dioxide

A

A

A

A

A

A

A

A

A

A

stroma

oxidative phosphorylation

water

cytoplasm

Krebs cycle

glycolysis

thylakoids

oxygen

Calvin cycle

lightdependent reaction

B

B

B

B

B

B

B

B

B

B

An example of Concept Map using both the “A” and “B” cards: