HOMEWORK WORKSHEET Chapter 4.1-4.3 4.1 – Chemical Energy and ATP 1. How are ATP and ADP related? High-energy ATP molecules are converted into lower-energy ADP molecules when a phosphate is removed and energy is released. ADP is converted back into ATP by the addition of a phosphate. 2. What types of molecules are broken down to make ATP? Which are most often broken down to make ATP? Carbohydrates, lipids (fats/triglycerides), and proteins; lipids and carbohydrates are the main sources of ATP. 3. How are some organisms able to survive without sunlight and photosynthesis? Chemosynthetic organisms use chemicals from their environment to make high energy carbon-based molecules. 4. How are the energy needs of plant cells to those of animal cells? How are they different? Both plants and animals use ATP to power cell functions. Plants make their own food to be broken down to make ATP; animals must consume other organisms for the food that is broken down to make ATP. Molecule Type Energy (Cal/mg) Details 5. Carbohydrate 4cal/mg Glucose: molecule most commonly broken down; glucose yields about 36 ATP. 6. Lipid 9cal/mg Fats (Triglycerides): Usually stored in the body for later use; yields 146 ATP. 7. Protein 4cal/mg Amino Acids: Least broken down, only broken down in emergencies 36 ATP. 4.2 – Overview of Photosynthesis Label the picture 10. Why are photosynthetic organisms called producers? They produce the source of chemical energy for themselves and for other organisms. 11. What is chlorophyll? A molecule in chloroplasts that absorbs some of the energy in visible light. 12. In which two parts of a chloroplast does photosynthesis take place? The stroma and grana. 13. What are thylakoids? They are coin-shaped, membrane-enclosed compartments inside the grana of the chloroplast. 14. What are the differences between the light-dependent reactions and the light-independent reactions? The lightdependent reactions require light, and they absorb and transfer energy. The light-independent reactions do not directly need light, and they build sugars. 15. Describe the stages of photosynthesis. Use the terms thylakoid, light-dependent reactions, and light-independent reactions in your answer. The first stage of photosynthesis is the light-dependent reactions that take place in the thylakoids. Energy is absorbed from sunlight and transferred through the thylakoid membrane. The energy is used in the light-independent reactions to produce sugars 16. Suppose you wanted to develop a light to help increase plant growth what characteristics should the light have? Why? The light should emit the optimal wavelengths, such as blue and red, to be absorbed by the pigments in plants 17. Overall, do you think photosynthesis endothermic or exothermic? Explain your answer. Endothermic; it absorbs energy to produce sugars. 18. What roles do electrons and hydrogen (H+) ions play in the light-dependent reactions of photosynthesis? Electrons transfer energy, and hydrogen ions flow through ATP synthase to produce ATP. 19. Describe how the light-independent reactions are the synthesis part of photosynthesis. The light-independent reactions build or put together sugars from carbon dioxide 4.3 – Photosynthesis in Detail 1. Fill in the cycle diagram to place the major steps of the Calvin cycle in the right order. Calvin Cycle steps: • The high yielding three 6-carbon molecules are reduced by the removal and formation of a three-carbon molecule that exits the cycle to await another round in the formation of glucose. • Three carbon dioxide molecules are added to a set 3-5 carbon molecules (RuBP) already in the Calvin cycle to make three 6-carbon molecules. • The formation of a high yielding 6-carbon molecule need for biological processes The 6-carbon molecules are rearranged by the addition of NADPH and ATP to make three high energy 6-carbon molecules • The three 6-carbon molecules are rearranged by the addition of NADPH and ATP to make three high energy 6-carbon molecules • The 3- 5-carbon molecule (RuBP) in the Calvin cycle is regenerated to pick up three more carbon dioxide molecules. 2. Use the table below and place the following in the right step order for the light-independent reaction: • Energy absorbed from sunlight and transferred to electrons that have entered the electron transport chain. • High-energy electrons are used to produce an energy-carrying molecule called NADPH. • The H+ ions diffuse back through the thylakoid membrane by passing through the ATP synthase channel to produce ATP. • Water molecules are broken down; electrons enter electron transport chain. • Energy from electrons in transport chain is used to pump H+ ions across the thylakoid membrane. Step 1 2 3 4 5 Description Water molecules are broken down; electrons enter electron transport chain. Energy absorbed from sunlight and transferred to electrons that have entered the electron transport chain. Energy from electrons in transport chain is used to pump H+ ions across the thylakoid membrane. High-energy electrons are used to produce an energy-carrying molecule called NADPH. The H+ ions diffuse back through the thylakoid membrane by passing through the ATP synthase channel to produce ATP. 3. Which molecules carry energy to the light-independent reactions? NADPH and ATP 4. What happens during the Calvin cycle? A series of chemical reactions use ATP and NADPH from the lightdependent reactions to make high yielding energy 6-carbon sugar molecules from low-energy carbon dioxide. 5. What is the electron transport chain? A series of proteins in the thylakoid membrane along which energized electrons travel. 6. What are the three parts of the light-dependent reactions? Photosystem II, photosystem I, and ATP synthase 7. What are photosystems? Molecules that are able to capture the energy from the sun and transfer along the electron transport chain. 8. What are the functions of photosystem II? Absorb energy and transfer energy to electrons that go into the electron transport chain; break down water; pump hydrogen ions across the thylakoid membrane 9. What are the functions of photosystem I? Absorb energy and transfer energy to electrons in the electron transport chain; produce NADPH to carry energy 10. What is the function of ATP synthase? To produce ATP as hydrogen ions flow through the enzyme 11. Explain the relationship between the light-dependent and the light-independent reactions. The light-dependent reactions absorb energy from sunlight and transfer the energy to the light-independent reactions that produce sugars. 12. Write the chemical equation for photosynthesis. 6CO2 + 6H2O → C6H12O6 + 6O2 13. Explain why the chemical equation for photosynthesis (above) is a highly simplified representation of the process. How is the equation accurate? How is it inaccurate? The equation shows the general reactants and products of the process. However, it does not show intermediate steps. For example, carbon dioxide and water do not actually react with each other.
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