BIOL 204 002.Plant.Physiology.Review.Questions

BIOL 204 002.Plant.Physiology.Review.Questions -...

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Photosynthesis 1. What are the differences in C3 and C4 photosynthesis? In C 3 photosynthesis, the more common type learned in class, CO 2 is incorporated into a three carbon compound, stomata are open during the day, rubisco is involved in the uptake of photosynthesis, photosynthesis takes place throughout the leaf, and it is more efficient than C 4 plants under cool and moist conditions because it requires less machinery. C 4 photosynthesis involves CO 2 being incorporated into a four-carbon compound from the outset. Stomata are open during the day. Uses PEP carboxylase for the enzyme involved in the uptake of CO 2 , which then “delivers” the CO 2 to rubisco. Photosynthesis takes place in inner cells near to the vascular bundle sheath and requires a special anatomy called the Krantz anatomy. 2. What is the function of Krantz anatomy in C4 leaves? Krantz anatomy sets a cellular barrier between the cells where rubisco fixes carbon and the open air where CO 2 is diffused. These cells work to slow down the diffusion of O 2 so as to prevent photorespiration. 3. What are the benefits of C4 photosynthesis? The benefits of C 4 photosynthesis are a reduction of photorespiration resulting from a decrease in O 2 concentration where rubisco is found. This allows the stomata of plants to remain open during the day in hot climates. 4. What are the costs of C4 photosynthesis? C 4 photosynthesis requires a greater amount of energy to maintain the system, and a lesser efficiency in photosynthetic production. 5. Where would you expect to find C4 plants? Hot climates that are somewhat dry but not necessarily in deserts (where we would find CAM plants) 6. Content Review Questions 1-4 and 6. 7. Conceptual Review Questions 3-6. a. Sketch the Z-scheme. Explain how photosystem I and photosystem II interact by tracing the path of an electron through the Z-scheme. What molecule connects the two photosystems? b. In what sense does photorespiration undo photosynthesis? Photorespiration consumes ATP as well as releases CO 2 , much like cellular respiration. Photosynthesis requires ATP to fix CO 2 into carbohydrates. c. Make a sketch showing how C 4 photosynthesis and CAM separate CO 2 acquisition from the Calvin cycle in space and time, respectively.
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d. Why do plants need both chloroplasts and mitochondria? Because while photosynthesis does a great job of converting light energy to the energy of bonds in hydrocarbons, the plant cells still require the work of mitochondria to convert the energy in carbohydrates into the energy found in ATP. 8. In measuring photosynthesis in a crop species you find that two species respond differently to a decrease in the concentration of O 2 in the gas surrounding the leaf. One species, (A) maintains a constant rate of photosynthesis in both high and low O 2 concentration, while another exhibits a significant increase in photosynthesis in the low O 2 environment. a.
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This note was uploaded on 02/02/2011 for the course BIOL 204 taught by Professor Toolson,e. during the Spring '08 term at New Mexico.

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BIOL 204 002.Plant.Physiology.Review.Questions -...

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