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Pasteur Effect, Glucose, Photosystem, and Other Short Answer Questions

1) Louis Pasteur (a French biochemist) investigated the metabolism of yeast which can survive under aerobic or anaerobic conditions. He observed that the yeast consumed sugar at a much faster rate under anaerobic conditions than it did under aerobic conditions. Explain this Pasteur effect.

2) If a plant is kept for many days in the dark, glucose is not produced, even though the sugar producing reactions are called light-independent. Why is glucose not produced in this case?

3) Explain how the leaf is adapted for capturing energy from the Sun and acquiring carbon dioxide and water.

4) The insecticide rotenone inhibits one of the steps of the electron transport system in mitochondria. What is the immediate result?

5) Describe the two major components of a photosystem. What is the function of each?

6) The dinosaurs likely died off from a lack of sunlight. What does this statement imply about the extinction of the dinosaurs?

7) Describe the properties of a biological catalyst.

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1) Louis Pasteur investigated the metabolism of yeast, which can survive under aerobic or anaerobic conditions. He observed that the yeast consumed sugar at a much faster rate under anaerobic conditions than it did under aerobic conditions. Explain this Pasteur effect.

Response: Fermentation (anaerobic respiration) in yeast essentially amounts to glycolysis with a side-reaction of converting pyruvate into ethanol and carbon dioxide. However, glycolysis only produces 2 net ATP molecules while full aerobic respiration (Krebs cycle and oxidative phosphorylation) produces 36 ATP. Therefore, in order for the yeast cells to continue growing at the same rate, they've got to increase the rate of glycolysis tremendously in order to keep producing the same amount of ATP to meet its cellular requirements.

2) If a plant is kept for many days in the dark, glucose is not produced, even though the sugar producing reactions are called light independent. Why is glucose not produced in this case?

Response: The "dark reaction" should really be called the "light-independent reaction." The light independent reaction is not DIRECTLY dependent on light, but it is indirectly dependent on light, because the light reaction produces NADPH as one of its outcomes. Right? This NADPH is used in the dark reaction to reduce CO2 into glucose. However, if the light reaction comes to a stop then eventually all of the stored NADPH will be used up and therefore, even the dark ...

Solution Summary

The solution gives short answers to each question (approx. 100 words per question) for a total of 939 words.

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