I. How do biological organisms use energy?1

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1 Name: Per: Photosynthesis, Cellular Respiration and Energy Concept Practice Packet Date: I. How do biological organisms use energy?1 IA. The Importance of ATP Living organisms use a two- step process to provide the energy needed for most biological processes. I. First, cellular respiration makes ATP from ADP plus a phosphate (P). The energy for this chemical reaction is provided by the cellular respiration of sugars or other organic molecules. II. Then, the hydrolysis of ATP provides the energy for most biological processes. When ATP and water react to form ADP plus a phosphate, this reaction provides the energy for many different cellular processes. Notice that the role of ATP in biological organisms is somewhat similar to the role of money in our society. Most people use a two- step process to get food, clothing, etc. I Cellular respiration of sugars or other organic molecules provides the energy to make ATP. Most people work to earn money. II Then, the hydrolysis of ATP provides the energy for most biological processes. Then people spend their money to buy the things they need or want. By Dr. Ingrid Waldron, University of Pennsylvania, Teachers are encouraged to copy this Student Handout for classroom use. A Word file (which can be used to prepare a modified version if desired), Teacher Notes with instructional suggestions, background information and alignment with Next Generation Science Standards are available at 1 1

2 1. Give one reason why the reaction, ADP + P à ATP + H 2O, requires energy input. (Hint: Notice the charges of the molecules in the top figure.) 2a. Inside each cell, there is a constant cycle of synthesis and breakdown of ATP. Add to this diagram to show: how cellular respiration contributes to the production of ATP how the hydrolysis of ATP to form ADP + P is useful. 2b. Explain why a cell needs to constantly break down and synthesize ATP. IB. Cellular Respiration The chemical equations shown below summarize the cellular respiration of glucose (a simple sugar). Glucose and oxygen are the inputs for a series of chemical reactions which provide the energy to make ATP from ADP + P. The actual process of cellular respiration in cells requires many steps which are not shown here. 3. Write the names of each of the molecules in these chemical equations. 4. How do our bodies get glucose and other organic molecules for cellular respiration? 5. Why do we need to breathe all day and all night? 6a. If you search for "cellular respiration equation" on the web, some of the most popular sites give the following chemical equation for cellular respiration of glucose. C 6H 12O O 2 6 CO H 2O + ATP What is wrong with this chemical equation? (Hint: Think about where the atoms in an ATP molecule come from.) 2

3 6b. Write a corrected version of this chemical equation that gives a more accurate summary of cellular respiration. (Hint: This corrected chemical equation should combine the two coupled reactions shown in the middle of this page.) IC. Using ATP to Provide Energy for Biological Processes The hydrolysis of ATP provides the energy for many biological processes, including mechanical work, pumping ions into or out of a cell, and synthesizing molecules (see second figure on page 1). 7a. The coupled reactions shown below summarize how hydrolysis of ATP provides the energy for muscle cells to contract. Fill in the blanks to complete the top line. many + many H 2O muscle cell relaxed many + many P muscle cell contracted 7b. The bottom line represents the reactions of muscle proteins that result in muscle contraction. What does represent? 8a. The reaction, ATP + H 2O ADP + P occurs: a. only in muscle cells b. in muscle cells and nerve cells c. in all the cells in your body. 8b. What reasoning supports the answer you chose? Two important general principles about energy are: Energy can be transformed from one type to another (e.g. chemical energy can be transformed to the kinetic energy of muscle contraction). However, energy can not be created or destroyed by biological processes. All types of energy transformation are inefficient. For example, the energy for muscle contraction is provided by the hydrolysis of ATP, but only about 20-25% of the energy from this chemical reaction is captured in the kinetic energy of muscle contraction. The rest of the energy is converted to heat. 9. Cellular respiration takes place primarily in organelles called mitochondria. Some textbooks claim that "Mitochondria make the energy needed for biological processes." Explain what is wrong with this sentence and give a more accurate sentence. 10. Explain why your body gets warmer when you are physically active. 3

4 II. Where does a plant's mass come from? 2 (from "Hard- to- Teach Biology Concepts" by Susan Koba with Anne Tweed, NSTA Press) 1. Which of the four hypotheses in the cartoon do you agree with? In this activity, you will analyze information to evaluate these four hypotheses. Almost all of a plant s mass consists of water and organic molecules (e.g. cellulose and proteins). The weight of all the organic molecules is called the biomass. 2. This pie chart for a plant s mass shows that more than half of a plant s mass is. (organic molecules/water) In plants, organic molecules are made largely from sugars which are produced by photosynthesis. 3a. Which chemical equation correctly summarizes how photosynthesis in plants produces the sugar, glucose? Explain how the other chemical equation violates a basic principle that applies to all chemical equations. sunlight a. 6 CO H 2O C 6H 12O O 2 sunlight b. 6 CO H 2O 6 C 6H 12O 6 + O 2 3b. Which of the input molecules for photosynthesis comes from the air? 3c. Which of the input molecules for photosynthesis comes from the soil? 2 By Dr. Ingrid Waldron, Department of Biology, University of Pennsylvania, 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 4

5 3d. Can the energy in sunlight be converted to the C, H or O atoms in glucose? yes no This figure shows how photosynthesis in chloroplasts inside plant cells produces sugars and these sugars are transformed into the different types of organic molecules that become part of growing plant cells. 4. The CO 2 needed for photosynthesis enters the plant through the. (leaves/roots) The water in the plant cells vacuoles and cytoplasm (including the water used for photosynthesis) enters the plant through the. (leaves/roots) 5. Explain how a carbon atom from a CO 2 molecule in the air can end up as a carbon atom in a protein in a plant cell. 6a. In , Helmont carried out a classic experiment to evaluate where a plant s mass came from. He grew a willow tree in a pot and added only water during the five- year experiment. He recorded the weight of the tree and the weight of the dried soil in the pot at the beginning and end of his experiment. Complete this table to show the changes in weight for the tree and for the dried soil. Weight of Tree Weight of Dried Soil pounds 200 pounds pounds, 3 ounces 199 pounds, 14 ounces Change in Weight 6b. Helmont concluded that almost none of the weight of the tree came from the dry soil, so almost all of the weight of plants comes from water. Is his conclusion justified by the findings from his experiment? yes no Explain why or why not. 5

6 6c. If Helmont's conclusion is not justified by the results of his experiment, state a more valid conclusion. 7. Complete the table below to summarize your evaluation of four hypotheses about where a plant s mass comes from. Use the information already presented and these research findings: Most of the mass of the sugar molecules produced by photosynthesis comes from CO 2. Most of the mass of plant organic molecules comes from these sugar molecules. Therefore, most of the mass of plant organic molecules comes from CO 2. Many plants can be grown with their roots in water instead of soil. However, growth and survival are limited unless a small amount of soil or fertilizer is added to the water. How much of a plant's mass comes from each of the following? The sun's energy a substantial amount a very small amount none Explain the evidence and reasoning that supports your conclusion. Molecules in the air that come into the plant s leaves a substantial amount a very small amount none Water taken up by the plant s roots a substantial amount a very small amount none Nutrients in the soil that are taken up by the plant s roots a substantial amount a very small amount none 6

7 III. Using Models to Understand Photosynthesis 3 A scientific model is a simplified representation of reality that highlights certain key features of a process, structure or system. A good model helps us to understand a process such as photosynthesis. During photosynthesis, plant cells use carbon dioxide, water, and the energy in sunlight to produce sugar molecules and oxygen. Some of the light energy is transformed to chemical energy in the sugar molecules. One model of photosynthesis is a chemical equation that summarizes the inputs and outputs of photosynthesis. Two different versions of this chemical equation are shown in this box. 1a. Write the names of the molecules in the first version of this chemical equation. 1b. For each type of molecule, draw a line that links the chemical formula in the first version of the equation with the corresponding diagram in the second version of the equation. 2. The chart below shows another type of model of photosynthesis. This chart emphasizes that: One type of energy can be transformed to another type of energy. One type of matter can be converted to another type of matter; i.e. the atoms in the input molecules are reorganized as the atoms in the output molecules. Energy is not converted to matter and matter is not converted to energy. Complete this chart to show the changes during photosynthesis. 3 By Dr. Ingrid Waldron, Dept. Biology, University of Pennsylvania, Teachers are encouraged to copy this Student Handout for classroom use. This Student Handout and Teacher Notes with instructional suggestions and background biology are available at 7

8 Photosynthesis takes place in chloroplasts inside leaf cells. This diagram of a chloroplast provides another model of photosynthesis. This model shows: some of the multiple steps involved in synthesizing a single sugar molecule a few of the many molecules needed for photosynthesis. Another important molecule is chlorophyll, a green pigment which absorbs light and begins the process of converting light energy to chemical energy. 3a. In this diagram, write the names of each type of input and output molecule for photosynthesis. 3b. Circle the part of the chloroplast where you would expect chlorophyll to be located. 4. A typical leaf is flat and thin, so each leaf cell is relatively near the surface of the leaf. How does this leaf shape help to maximize the rate of photosynthesis in leaves? 5. All three models of photosynthesis (the diagram above and the chemical equations and chart on page 1) show some of the same basic characteristics of photosynthesis. What are some basic characteristics of photosynthesis that are shown in all three of these models of photosynthesis? 6. For each type of model, describe one advantage that helps you to better understand photosynthesis. Advantage of the Chemical Equations (p. 7) Advantage of the Energy- Matter Chart (p. 7) Advantage of the Chloroplast Diagram (this page) 8

9 IV. How do muscles get the energy they need for athletic activity? 4 All athletic activity depends on muscle contractions that require energy. Inside muscle cells, the hydrolysis of ATP provides the energy for the molecular reactions that result in muscle contraction. A typical muscle cell at rest has only enough ATP for ~1 or 2 seconds of contraction. To continue contraction for more than 1 or 2 seconds, a muscle cell needs to restore the ATP molecules. Two processes can use glucose to produce ATP: aerobic respiration (Aerobic means that a process requires air or, specifically, oxygen = O 2. Aerobic respiration is also called cellular respiration.) anaerobic fermentation (Anaerobic means that the process does not require O 2.) 1a. In the diagram above, label the arrow that shows the hydrolysis of ATP. 1b. Label the arrow that shows energy input from anaerobic fermentation or aerobic respiration. Anaerobic fermentation and aerobic respiration are summarized in the coupled chemical reactions shown in the boxes below. In both processes, glucose is broken down to smaller molecules in chemical reactions that release energy which is used in the production of ATP. 2. Write in the names of the molecules in the first chemical equation in each box. (Anaerobic fermentation in muscles produces lactic acid.) Fill in the blanks in the last chemical equation shown. Anaerobic Fermentation Aerobic Respiration C6H12O6 2 C3H6O3 2 ADP + 2 P 2 ATP represents chemical reactions; C6H12O6 + 6 O2 6 CO2 +6 H2O ~29 + ~29 P ~29 represents energy transfer between coupled reactions 3. During vigorous physical activity a person breathes faster and deeper. This increases the supply of O 2 for the muscles. How does this contribute to better athletic performance? 4 By Dr. Ingrid Waldron, Biology Dept, Univ Pennsylvania, This Student Handout and Teacher Notes with instructional suggestions and background information are available at 9

10 Anaerobic fermentation and aerobic respiration produce most of the ATP for muscle contraction, but muscle cells can make a rapid, brief burst of ATP using creatine phosphate (also called phosphocreatine.) 4. Fill in the blanks in the first reaction below to show how hydrolysis of ATP provides the energy for muscle cells to contract. (Hint: See the top of page 1.) many + many H 2O muscle cell relaxed many + many P muscle cell contracted 5. During physical activity muscle cells have increased rates of anaerobic fermentation, aerobic respiration and/or the hydrolysis of creatine phosphate. Explain why it is useful for these rates to increase in muscle cells during physical activity. General Principles Energy can be transformed from one type to another (e.g. chemical energy can be transformed to the kinetic energy of muscle motion). Energy is not created or destroyed by biological processes. All types of energy transformation are inefficient and result in the production of heat. For example, when hydrolysis of ATP provides the energy for muscle contraction, only about 20-25% of the chemical energy released is captured in the kinetic energy of muscle contraction. The rest of the energy from the hydrolysis of ATP is converted to heat. The atoms in molecules can be rearranged into other molecules, but matter (atoms in molecules) is not created or destroyed. 6. Aerobic respiration occurs mainly inside the mitochondria in cells. A website claims that "The mitochondria in muscle cells make the energy needed for athletic activity." Explain what is wrong with this sentence, and give a more accurate sentence. 7. Explain why your body gets warmer when you are physically active. 10

11 You have seen that anaerobic fermentation and aerobic respiration of glucose provide the energy to produce ATP, and hydrolysis of ATP provides the energy for muscle contraction. The obvious next question is "How does glucose get to the muscles?" As shown in this chart, glucose can be derived from: carbohydrates in food (e.g. starch or sugars such as sucrose) glycogen (a polymer of glucose used to store glucose in muscles and in the liver). Then, glucose is carried by the blood from the digestive system to the muscles. Digestive System Mouth, stomach and small intestine - carbohydrates in food glucose Liver - glycogen many glucose blood Respiratory System - air in lungs O 2 blood Muscles - anaerobic fermentation and aerobic respiration of glucose provides the energy to produce ATP - glycogen many glucose Notice that the energy supply for muscle contraction depends on the cooperation of: the digestive system (to provide glucose) the respiratory system (to provide O 2) the circulatory system (since the blood pumped by the heart carries glucose and O 2 to the muscles). 8. The chart shows that at some times glycogen is broken down to release glucose, and at other times many glucose molecules are combined to form glycogen. Use an X to mark the arrows for the reaction that occur at a higher rate during vigorous exercise. Use an M to mark the arrows for the reaction that occurs at a higher rate during rest after a meal. During exercise, fat molecules stored in muscles and in adipose tissue are broken down to fatty acids which muscle cells can use as another input for aerobic respiration. 9. Regular aerobic exercise such as walking, running or swimming results in changes in the body called training effects. Complete the following table to explain how each listed training effect contributes to an increased capacity for aerobic respiration in muscle cells. Training Effect Produced by Regular Aerobic Exercise The heart can pump more blood per second and the muscles have more capillaries (small blood vessels where O 2, glucose, and fatty acids move from the blood to the muscle cells). Muscle cells have more and larger mitochondria and more enzymes for aerobic respiration. Explain how this training effect can contribute to an increase in the rate of aerobic respiration in muscle cells. Muscle cells have more stored glycogen and more of the molecules that facilitate uptake of glucose and fatty acids into cells. 11

12 In active muscle, both anaerobic fermentation and aerobic respiration produce ATP. In addition, creatine phosphate can be used to produce ATP. The relative importance of these three energy sources varies depending on the intensity and duration of the physical activity. To learn how the primary source of muscle ATP differs for races of different lengths, read the following information and answer questions Creatine phosphate can be used to produce ATP more rapidly than anaerobic fermentation or aerobic respiration. Muscle cells typically have enough creatine phosphate to supply ATP for ~10 seconds of intense activity. Anaerobic fermentation is faster than aerobic respiration and does not require O 2, so anaerobic fermentation can provide a lot of ATP for brief intense athletic events. However, anaerobic fermentation can only be a major source of energy for a minute or two, in part because anaerobic fermentation produces lactic acid and too much lactic acid has harmful effects. Aerobic respiration is the slowest of these processes, but aerobic respiration produces more ATP per glucose molecule than anaerobic fermentation and aerobic respiration can continue for hours. Running Distance Running Time (world record; US high school record) Speed 100 m 9.6 seconds; 10.0 seconds 10.4; 10.0 m/sec. 400 m 43.2 seconds; 44.7 seconds 9.3; 8.9 m/sec. Marathon (42.2 km) 2 hours 3 min. 23 sec.; 2 hours 23 min. 47 sec. 5.7; 4.9 m/sec. 10. What do you think is the primary source of ATP for muscles during a marathon? aerobic respiration anaerobic fermentation creatine phosphate Explain your reasoning. 11. Explain why creatine phosphate is the most important contributor to ATP production during a 100 m race and less important for longer races. 12. Explain why, for a 400 m race, anaerobic fermentation supplies more of the ATP than aerobic respiration. 13. Complete this table concerning two of the recovery processes that occur after an athletic event. Recovery Process In muscle cells and liver cells, glycogen is synthesized from glucose derived from food molecules. Explain why this recovery process is useful after a marathon which ended with an intense sprint. In liver cells, lactic acid is converted back to glucose. 12

13 V. Photosynthesis and Cellular Respiration VA. Understanding the Basics of Bioenergetics and Biosynthesis 5 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? 5 By Dr. Ingrid Waldron, Department of Biology, University of Pennsylvania, 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 13

14 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. 14

15 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. VB. 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? How does this process result in decreased biomass? Where does the mass go? cellular respiration photosynthesis 15

16 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 (seeds sprouted to produce plants) 3. Water, no light (seeds sprouted to produce plants) <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 16

17 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 (seeds sprouted to produce plants) 3. Water, no light (seeds sprouted to produce plants) 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. 17