1. Suppose botanists grow two groups of plant cells. Feel free to write on the m

Question

1. Suppose botanists grow two groups of plant cells. Feel free to write on the molecules to label them. • Group I: Cells grown in water containing a radioactively labeled oxygen atom (H2 18O) • Group II: Cells grown with carbon dioxide containing two radioactively labeled oxygen atoms (C 18O2)

a. Where should the botanists look to find the radioactive oxygen atoms (18O) in Group I? Explain.

b. Where should the botanists look to find the radioactive oxygen atoms (18O) in Group II? Explain.

2. A very ingenious Bi211 student thinks she has figured out a way to increase the production of carbohydrates from the photosynthesis reactions. She has figured out a way to pump extra H+ into the thylakoids of chloroplasts without disrupting any of the reactions that normally occur in photosynthesis.

a. How, specifically, would this affect the photosynthesis processes?

b. Why is this unlikely to increase the amount of carbohydrates produced?

Explanation / Answer

Q1. a) The radioactive oxygen atoms will be released as oxygen gas. The water is split up during the light reaction with the release of oxygen.

b) The radioactive oxygen in the carbon dioxide will be obtained from a compund called phosphoglyceric acid (PGA). This would happen because the atmospheric carbon dioxide is fixed as an organic compound.

Q2. a) This would not affect the process as the number of carbon dioxide molecule which is condensed to 3-PGA is critical. ATP is just providing energy and is not the limiting factor.

b) Number of carbohydrates depends on the number of carbon dioxide molecules initially used for the starting up reaction. Since that is not increasing, the increase in the amount of carbohydrates produced would be unlikely.

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