SA 8-1
1. The sun.
2. ATP stands for adenosine triphosphate, which is one of the principal chemical compounds that living things use to store energy and release it for cell work to be done
3. A typical answer might mention active transport, movements within the cell, synthesis of proteins and nucleic acids, or responses to chemical signals.
4. Autotrophs obtain energy by making their own food. Heterotrophs obtain energy from the foods they consume.
5. Similar: Both store chemical energy for a cell. Different: A single molecule of glucose stores more than 90 times the chemical energy of an ATP molecule.
SA 8-2
1. Van Helmont discovered that water was involved in increasing the mass of a plant. Priestley discovered that a plant produces the substance in air required for burning. Ingenhousz discovered that light is necessary for plants to produce oxygen.
2. Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars.
3. Light provides the energy needed to produce high-energy sugars. Chlorophyll absorbs light, and the energy of that absorbed light makes photosynthesis work.
4. Plants are green because green light is reflected by the chlorophyll in leaves.
5. The plant would not grow well because chlorophyll does not absorb much light in the yellow region of visible light.
SA 8-3
1. The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.
2. The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.
3. Light energy is converted into chemical energy by the pigments in the chloroplast.
4. The main function of NADPH is to carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell.
5. The light-dependent reactions provide the Calvin cycle with ATP and NADPH. The Calvin cycle uses the energy in ATP and NADPH to produce high-energy sugars.
CA 8
1. b 6. a
2. b 7. d
3. b 8. a
4. d 9. b
5. c 10. a
11. Autotrophs are able to obtain energy by making their own food. Heterotrophs obtain their energy by consuming food
12. An ATP molecule consists of a nitrogen-containing compound called adenine, a sugar called ribose, and three phosphate groups.
13. ATP resembles a fully charged battery because it can yield energy when the third phosphate group is removed, also forming ADP. ADP is like a partially charged battery that can be recharged when energy is added to link a third phosphate group, reforming ATP
14. A single molecule of glucose stores more than 90 times the energy stored by ATP. However, ATP, which transfers energy quickly, is used by the cell as an immediate source of energy.
15. Priestley discovered that plants produce a substance needed to burn candles, now known to be oxygen. lngenhousz found that plants produce oxygen only when exposed to light.
16. Carbon dioxide + water —> sugars + oxygen
17. Plant pigments absorb energy from light and transfer it to electrons involved in photosynthesis.
18. A: chloroplast; B: stroma; C: granum; D: thylakoid. The light- dependent reactions take place in the thylakoids. The Calvin cycle takes place in the stroma.
19. NADP+ carries energy by holding two electrons and a hydrogen ion. It carries the stored energy to other reactions that help build sugar molecules.
20. ATP synthase is a protein found in the thylakoid membrane that allows H+ ions to pass through it. As H+ ions pass through this protein, it rotates and binds ADP and a phosphate group together to produce ATP.
21. During the Calvin cycle, plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time. The Calvin cycle uses six molecules of carbon dioxide to produce a single 6-carbon sugar molecule.
22. The Calvin cycle uses the ATP and NADPH produced during the light-dependent reactions to produce high-energy sugars.
23. Factors that affect the rate of photosynthesis include the temperature, the amount of available water, and the intensity of light.
Critical Thinking
24. The chlorophyll may be broken down by the cooling temperatures or the changing light, so the green color disappears. The leaf then shows the color of its remaining pigment(s).
25. Some students may build on the analogy of the battery from the chapter. Others may develop a new analogy. For example, ADP is like a ball at the bottom of the hill, Moving the ball to the top of the hill is like adding a phosphate group and making ATP. The ball now has the energy to roll downhill and move other objects in its path. ATP has energy to help change molecules.
26. No step of the Calvin cycle depends directly on light. Instead, it uses energy stored in the molecules ATP and NADPH.
27. Students’ answers may include: Start with two samples of the same amount and type of pond algae in water. Put one sample in the dark and the other in a location that receives daylight, keeping the temperatures the same. After two weeks, compare the two samples to determine the amount and health of the algae.
28. a. The graph shows a curve that descends from left to right. The farther the light is from the plant, the fewer bubbles are produced.
b. 10 cm.
c. The closer the plant is to the light, the more oxygen is produced. This occurs because more light energy is reaching the algae cells and thus is available for photosynthesis.
29. At first, photosynthesis would take place during daylight, but it would stop when the water was used up. If no more water was added, the plant might die.
30. Because the Indian pipe plant has no chlorophyll or other pigment involved in photosynthesis, it probably cannot make its own food. Therefore, it must obtain food from other sources the way a heterotroph does. Perhaps it absorbs partly decayed food in the soil.