Question

In Class Activity- 10 photosynthesis Ch. Lab section Tue PM 8 pts. 1. C ompare the complete oxidation of glucose with the process of photosynthesis. Be sure to include free energy in your discussion along with reactants/products 2. Generally, oxidation reactions are exergonic and reduction is endergonic. Explain this in the context of respiration and photosynthesis. 3. Use the data in the graph below to explain why plants utilize both cyclic and non-cyclic electron transport ATP production stimulated by ent wavelengths of light Y4. You overhear Calvin and Benson arguing over the molecular building blocks of carbon fixation. Benson argues that for an organism to form carbohydrates, it needs to join a water molecule to a carbon molecule. He proposes the following experiment: feed photosynthetic algae radioactive water (H:0) as a tracer molecule, and then follow the fate of the oxygen. If you "traced" the water as it was utilized in photosynthesis, on what molecule would you find O'l at the end of the experiment? Explain your answer

Answer 1

Non cyclic electron flow is usually mostly coupled to reduction of NADP to NADPH which is used to fix CO2. But a little of this flow can be diverted to reduce O2 and nitrate. A big advantage of this "alternative" electron flow is that little or no ATP is consumed by the downstream processes but large amounts can be synthesized during this electron flow. Hence, temporary deficits in ATP availability for CO2 fixation and other biosynthetic processes can be corrected. Cyclic electron flow is another potential way of using light energy to make "extra" ATP. But, there is real controversy as to whether cyclic flow is actually coupled to synthesis of ATP.