Photosynthesis and Cellular Respiration Understanding the Basics of Bioenergetics and Biosynthesis 1 This figure shows the processes that plant cells use to provide the energy needed for many of the activities of life. First, photosynthesis uses the energy in sunlight to make glucose from carbon dioxide and water. Then, cellular respiration uses glucose and oxygen as inputs for reactions that release energy, which cellular respiration uses to make ATP from ADP and P. Finally, hydrolysis of ATP provides energy in the form needed for many biological processes. 1. In the figure, underline the names of each of the four inputs for cellular respiration. 2a. Photosynthesis produces glucose and oxygen. These molecules are inputs for. 2b. Cellular respiration produces carbon dioxide and water. These molecules are inputs for 2c. Notice that photosynthesis and cellular respiration make a cycle where the products of each process are inputs molecules for the other process. Draw an oval around the part of the figure that shows this cycle. 3a. Cellular respiration produces ATP and H 2O. These molecules are the inputs for 3b. The hydrolysis of ATP produces ADP and P. ADP and P are inputs for 3c. Cellular respiration and hydrolysis of ATP make a cycle where the products of each process are inputs for the other process. Draw a triangle around the part of the figure that shows this cycle. 4a. Why do plants need to carry out both photosynthesis and cellular respiration? 4b. Why do animals need to carry out cellular respiration, but not photosynthesis? 1 By Dr. Ingrid Waldron, Department of Biology, University of Pennsylvania, 2016. Teachers are encouraged to copy this Student Handout for classroom use. This Student Handout and Teacher Notes with background information and instructional suggestions are available at http://serendip.brynmawr.edu/exchange/bioactivities/photocellrespir. 1
To represent the overall chemical equations for photosynthesis and cellular respiration, you will use 16 rectangles. Divide a sheet of paper into 16 rectangles. For photosynthesis, prepare: four rectangles, each with one of the following: C 6H 12O 6, 6 CO 2, 6 H 2O, 6 O 2; write the name of the molecule represented by each chemical formula one rectangle with to represent a chemical reaction two rectangles with + one rectangle with sunlight For cellular respiration, you will need all of the photosynthesis rectangles except the last, plus: four rectangles, each with one of the following: ~29 ATP, ~29 ADP, ~29 P, ~29 H 2O one additional rectangle with two additional rectangles with + one rectangle with \/ to represent energy transfer between coupled reactions \/ 5. Arrange the eight rectangles for photosynthesis to show the overall chemical equation for photosynthesis. Copy this chemical equation into the top box in this chart. Photosynthesis Cellular Respiration 6. Rearrange the photosynthesis rectangles (except for sunlight) to show the first chemical equation for cellular respiration. Arrange the rest of the rectangles to show the rest of the process of cellular respiration. Copy these chemical equations for cellular respiration into the bottom box in the above chart. 7. Draw two arrows to show how the products of photosynthesis can be used as the inputs for cellular respiration. Next, draw two arrows to show how the products of cellular respiration can be used as the inputs for photosynthesis. 8. What happens to the ATP produced by cellular respiration? Show the chemical reaction. Explain how this reaction is useful. 2
Not all of the sugar molecules produced by photosynthesis are used for cellular respiration. Some of the sugar molecules are used to synthesize other organic molecules. For example, multiple glucose molecules are joined together to make starch or cellulose. 9a. Circle one glucose monomer in each polymer in the figure. 9b. Why do plants need to make cellulose? 9c. Why is it useful for plants to make starch molecules? Give a specific example of how starch molecules are useful for a plant. The sugars produced by photosynthesis are also used to make other plant molecules, such as the amino acids which are the building blocks for proteins. 10. The sugars produced by photosynthesis are used for two different purposes: Some of the sugar molecules are used for cellular respiration to produce which provides energy for the processes of life. Some of the sugar molecules are used to synthesize. 11. A plant is made up primarily of: organic molecules like cellulose and proteins water molecules. To grow, plants add more organic molecules and water. Draw a flow chart or diagram to show: how plants make the organic molecules needed to grow how plants get the carbon dioxide and water needed for photosynthesis and growth. Plant Growth Puzzle Biomass is the weight of the organic molecules in an organism, after the water has been removed. Thus, biomass = an organism s weight - the weight of the water in the organism. 12. Which process can result in decreased biomass for a plant? cellular respiration How does this process result in decreased biomass? Where does the mass go? photosynthesis 3
13. Which process can contribute to increased biomass for a plant? cellular respiration photosynthesis Where does the increased biomass come from? What molecules are taken in by the plant and used to create organic molecules that become part of the plant's biomass? 14. A typical seed contains many starch and/or fat molecules. When a seed germinates and a plant first begins to grow, these starch and fat molecules are broken down to provide glucose and fatty acids, which can be used as input for cellular respiration to produce ATP. When a seed begins growing underground in the dark, the plant cannot carry out because (cellular respiration/photosynthesis) there is no light. A plant growing in the dark will only carry out (cellular respiration/photosynthesis) and the plant will biomass. (gain/lose) An experimenter evaluated the change in biomass for seeds kept in petri dishes under three different conditions (shown in the top row of the table below). At the beginning of the experiment each batch of seeds weighed 1.5 grams. The seeds had very little water, so each batch of seeds had 1.46 grams of biomass. After ten days, the seeds that were exposed to water had sprouted to produce plants. To determine the biomass of each batch of seeds/plants, they were dried in an oven overnight (to remove all the water) and then weighed. 15. For each condition in the table below, predict the biomass after 10 days. Explain why you predict a decrease, increase or no change from the initial 1.46 grams of biomass. Condition for each batch of seeds Predicted biomass at 10 days (grams) 1. Light, no water (seeds did not sprout) 2. Light, water 3. Water, no light <1.46 ~1.46 > 1.46 <1.46 ~1.46 > 1.46 <1.46 ~1.46 > 1.46 Reason for predicting decrease, increase or no change in biomass 4
16. Your teacher will tell you the results of the experiment. Enter the observed results in this table. If any of the observed results differ from your predictions in question 15, explain the biological reasons for the observed results. Condition for each batch of seeds Observed biomass at 10 days (grams) Did this result match your prediction? If any result did not match your prediction, explain a possible reason for the observed result. 1. Light, no water (seeds did not sprout) 2. Light, water 3. Water, no light yes no yes no yes no A paradox is observed when you compare the results observed for the seeds in light, but no water vs. the plants that developed with water, but no light. Comparison of Results for: Seeds in light, no water vs. Plants in no light, water More biomass More volume and more total weight 17. What explanation can account for this paradox? In other words, explain why: the seeds in light, with no water had more biomass than the plants that developed with water, but no light, but the plants had more volume and more total weight than the seeds. 5