Chapter 8: Photosynthesis

Transcription

1 Chapter 8: Photosynthesis Cellular Basis of Life Q: How do plants and other organisms capture energy from the sun? WHAT I KNOW WHAT I LEARNED 8.1 How do organisms store energy? 8.2 What cellular structures and molecules are involved in photosynthesis? 8.3 How do photosynthetic organisms convert the sun s energy into chemical energy? 8.1 Energy and Life Chemical Energy and ATP For Questions 1 6, complete each statement by writing the correct word or words. 1. ENERGY is the ability to do work. 2. The main chemical compound cells use for energy is ADENOSINE TRIPHOSPHATE (ATP). 3. RIBOSE is a 5-carbon sugar molecule that is part of an ATP molecule. 4. The PHOSPHATE GROUPS of ATP are the key to its ability to store and supply energy. 5. ATP releases energy when it BREAKS bonds between its phosphate groups. 6. Most cells only store enough ATP for A FEW SECONDS of activity.

2 7. Label each part of the diagram of an ATP molecule below. For Questions 8 10, refer to the Visual Analogy comparing ATP to a charged battery. 8. In the visual analogy, what chemical is represented by the low battery? ADP 9. What are two ways in which the diagram shows an increase in energy? BRIGHTER FLASHLIGHT BEAM; SUNBURST 10. Describe the concepts shown in the diagram. WHEN A PHOSPHATE GROUP BREAKS OFF, THE REMAINING ADP MOLECULE STORES VERY LITTLE ENERGY. WHEN A PHOSPHATE GROUP IS ADDED TO ADP, THE RESULTING ATP MOLECULE STORES MORE ENERGY

3 11. What are two ways in which cells use the energy temporarily stored in ATP? ACTIVE TRANSPORT, CELL MOVEMENT, BIOLUMINESCENCE, MAKING PROTEINS 12. Energy is needed to add a third phosphate group to ADP to make ATP. What is a cell s source of this energy? FOOD MOLECULES SUCH AS SUGARS AND STARCHES PROVIDE THE ENERGY Heterotrophs and Autotrophs For Questions 13 17, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. T 13. All heterotrophs must eat food to get energy. T 14. Autotrophs do not need to eat food because they make food. F, SUN 15. The energy in food originally came from ATP. F, PUTTING TOGETHER 16. The term photosynthesis means pulling apart with light in Greek. T 17. The energy of sunlight is stored in the chemical bonds of carbohydrates. 18. Complete the table comparing two types of organisms. Autotrophs and Heterotrophs Type Description Examples Autotrophs ORGANISMS WHO MAKE THEIR OWN FOOD Heterotrophs ORGANISMS THAT OBTAIN ENERGY FROM THE FOOD THEY EAT GRASS, ALGAE, (SOME) BACTERIA CHEETAH, HARE, MUSHROOM Apply the Big idea 19. Suppose that you ate a hamburger on a wheat roll with lettuce, tomatoes, and onions for lunch. As you ate, you took in food molecules from plants and animals. Explain why all the energy in the food molecules of this hamburger could be traced back to the sun. The bread, lettuce, tomatoes, and onions in a hamburger all came from plants. The food molecules in those plants were made as a result of the process of photosynthesis, using the energy in sunlight. The hamburger meat came from a cow, which ate grass and other plants to obtain food. The cow made the molecules in the meat by using energy in the food molecules from the plants, which originally came from the sun. 8.2 Photosynthesis: An Overview Chlorophyll and Chloroplasts For Questions 1 6, complete each statement by writing the correct word or words. 1. The WAVELENGTH of light determines its color. 2. Chemicals that absorb light are called PIGMENTS. 3. Chlorophyll makes plants look green because it REFLECTS green light. 4. Chloroplasts contain an abundance of saclike photosynthetic membranes called THYLAKOIDS. 5. The STROMA is the fluid portion of the chloroplast located outside the thylakoids. 6. The visible light absorbed by chlorophyll RAISES the energy level of the chlorophyll s electrons.

4 7. Label the internal parts of the chloroplast below. STROMA THYLAKOID GRANA High-Energy Electrons For Questions 8 9, refer to the Visual Analogy comparing electron carriers to oven mitts. 8. In the visual analogy of carrying electrons, what represents the high- energy electrons? HOT POTATO 9. Write another analogy that describes the process of electron carriers. 10. Where do the high-energy electrons carried by NADPH come from? CHLOROPHYLL MOLECULES THAT HAVE ABSORBED SUNGLIGHT An Overview of Photosynthesis For Questions 11 13, write the letter of the correct answer on the line at the left. B 11. What are the reactants of the photosynthesis reaction? A. chlorophyll and light C. carbohydrates and oxygen B. carbon dioxide and water D. high-energy electrons and air C 12. What are the products of the light-dependent reactions? A. chloroplasts and light C. oxygen and ATP B. proteins and lipids D. water and sugars A 13. Where do the light-independent reactions occur? A. stroma C. chlorophyll

5 B. thylakoids D. mitochondria 14. Complete the illustration by writing the reactants and products of the light-dependent and light-independent reactions. Also, fill in the energy source that excites the electrons. WATER CARBON DIOXIDE LIGHT OXYGEN GLUCOSE 15. Solar power uses cells or panels to absorb the sun s energy. That energy is then used to create electricity. How does this compare to the light dependent reactions of photosynthesis? BOTH USE ENERGY FROM THE SUN TO CREATE ENERGY. CHLOROPLASTS ACT LIKE SOLAR CELLS, ABSORBING THE SUN S ENERGY AND TRANSFERRING IT TO THE ELECTRONS IN CHLOROPHYLL, WHICH RAISES THE ENERGY LEVEL OF THE ELECTRONS. THE HIGH-ENERGY ELECTRONS ARE PICKED UP BY CARRIERS AND USE TO POWER CHEMICAL REACTIONS. 8.3 The Process of Photosynthesis The Light-Dependent Reactions: Generating ATP and NADPH For Questions 1 5, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. T 1. Photosystems are clusters of chlorophyll and proteins. F, PSII 2. The light-dependent reactions begin when photosystem I absorbs light. T 3. Electrons from water molecules replace the ones lost by photosystem II. NADPH 4. ATP is the product of photosystem I. ENERGY 5. ATP and NADPH are two types of protein carriers.

6 6. How does ATP synthase produce ATP? ATP SYNTHASE ALLOWS H IONS TO PASS THROUGH THE THYLAKOID MEMBRANE. AS THE IONS PASS THROUGH THEY CAUSE THE ATP SYNTHASE TO SPIN/ROTATE WHICH CAUSES THE ENERGY NECESSARY TO ADD A PHASOPHATE GROUP TO ADP, MAKING ATP 7. When sunlight excites electrons in chlorophyll, how do the electrons change? ELECTRONS GET EXCITED THEY TAKE ON A GREAT DEAL OF ENERGY WHICH CAUSES THEM TO MOVE TO A HIGHER ENERGY LEVEL 8. Where do the light-dependent reactions take place? THYLAKOID MEMBRANE 9. Complete the table by summarizing what happens in each phase of the light-dependent reactions of photosynthesis. Light-Dependent Reactions Photosystem II Summary P II absorbs light and increases the electrons E level. Electrons are passed to ETC. Enzymes in thylakoid break water into 2 electrons, 2 H ions, and 1 O atom. The 2 electrons replace the high energy electron that have been lost to ETC Electron Transport Chain E from electrons is used by the protein in the chain to pump H ions from the stroma into the thylakoid membrane space (generating a H ion gradient) At the end of the ETC the electrons are passed to PI Photosystem I Electrons do not have as much energy as they used to and are re-energized by light energy in pi. At the end of another short ETC, NADP in the stroma picks up the high energy electrons (along with H ions) to become NADPH Hydrogen Ion Movement and ATP Formation H ions began to accumulate within the thylakoid membrane. The build of H ions makes the stroma negatively charged relative to the space within the thylakoid. This gradient provides the energy to make ATP The Light-Independent Reactions: Producing Sugars 10. What does the Calvin cycle use to produce high-energy sugars?

7 CARBON DIOXIDE AND THE PRODUCTS OF THE LIGHT REACTIONS (ATP, NADPH) 11. Why are the reactions of the Calvin cycle called light-independent reactions? THEY DO NOT REQUIRE DIRECT SUNLIGHT (BUT THEY DO REQUIRE THE PRODUCTS OF THE LIGHT REACTIONS) 12. What makes the Calvin cycle a cycle? RUBP IS REGENERATED AT THE END OF THE CYCLE 13. Complete the diagram of the Calvin cycle by filling in the missing labels. 12 C-C-C 6 C-C-C-C-C (RUBP) 12 ADP 6 ADP 12 NADP+ 12 C-C-C (PGAL/G3P) 10 C-C-C Factors Affecting Photosynthesis 14. What are three factors that affect the rate at which photosynthesis occurs? TEMPERATURE, LIGHT INTENSITY, WATER AVAILABILITY 15. Would a plant placed in an atmosphere of pure oxygen be able to conduct photosynthesis? Explain your answer. NO; PLANTS REQUIRE CO Complete the table about variations of photosynthesis. Type Description Examples

8 C4 CAM Occurs in plants that have a specialized chemical pathway that allows them to capture even very low levels of carbon dioxide and pass it to the Calvin cycle. CAM PLANTS ONLY ALLOW AIR INTO THEIR LEAVES AT NIGHT WHICH MINIMIZES WATER LOSS; CO 2 IS TRAPPED IN THE LEAVES AND IS RELEASED DURING THE DAY, ENABLING CARBOHYDRATE PRODUCTION CORN, SUGAR CANE pineapple trees, many desert cacti, and ice plants 17. Photosynthesis plays an important role in supplying energy to living things. Considering what the products of photosynthesis are, what is another way in which photosynthesis is vital to life? PHOTOSYNTHESIS IS THE WAY IN WHICH NEW ORGANIC MOLECULES ARE ADDED TO THE LIVING PORTION OF THE BIOSPHERE; ALL LIVING THINGS RELY ON THE PHOTOSYNTHESIS AS A SOURCE OF THE ORGANIC BUILDING BLOCKS NEEDED FOR GROWTH