MCB 450 SU11_Exam III_KEY

MCB 450 SU11_Exam III_KEY - Name:_NetID:_ Please print your...

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Name:________________________________________ NetID:______________________________ 1 Please print your Name and NetID at the top of ALL pages of this exam. Only non-graphing calculators are permitted for use on this exam. MCB 450 Summer 2011 Exam III KEY August 4, 2011 Part I: Multiple choice (2 points each; total 60 points) 1. Which of the following reactions is/are NOT part of photosynthetic light reactions? A. CO 2 fixation B. Oxidation – Reduction C. Phosphorylation D. N 2 fixation E. Both A and D 2. The enzyme Rubisco catalyzes the reaction of ribulose-1,5-bisphosphate with CO 2 (Calvin cycle) or alternatively with O 2 (photorespiration). Photorespiration limits CO 2 fixation. C4 plants are more efficient users of light energy for carbohydrate synthesis because: A. C4 plants do not undergo the Calvin cycle B. C4 plants contain a mutated rubisco enzyme that cannot react with O 2 C. C4 plants circumvent photorespiration by sheltering the Calvin cycle in an interior cellular compartment where [O 2 ] is low D. C4 plants make the pH in the stroma highly acidic such that the enzyme rubisco cannot efficiently react with O 2 E. Both C and D
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Name:________________________________________ NetID:______________________________ 2 3. Which of the following can be substrates for gluconeogenesis in animals? A. Acetyl-CoA B. Fatty acids C. Lactate D. Pyruvate E. Both C and D 4. Glycolysis and gluconeogenesis cannot be merely the reverse of each other because: A. Glycolysis occurs in the cytosol and gluconeogenesis in the mitochondria B. Glycolysis is exergonic and hence gluconeogenesis would be highly endergonic if it were merely the reverse of glycolysis C. Glycolysis and gluconeogenesis must be coordinately regulated in a reciprocal fashion D. Glycolysis requires water-soluble enzymes, while gluconeogenesis requires membrane-bound enzymes E. Both B and C 5. Pyruvate carboxylase is one of the unique enzymes of gluconeogenesis which converts pyruvate to oxaloacetate. What happens to the activity of the enzyme when acetyl-CoA levels are high? A. Inhibited B. Activated C. No change in activity D. Depends on the abundance of pyruvate carboxylase E. Depends on whether pyruvate carboxylase is exclusively present in the mitochondrial matrix or the cytosol
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Name:________________________________________ NetID:______________________________ 3 6. The first step in glycogen catabolism (catalyzed by the enzyme glycogen phosphorylase) is a phosphorolysis reaction (analogous to hydrolysis) where cellular P i attacks the nonreducing end of the glycogen molecule. The advantage(s) of a phosphorolysis reaction (as compared to a hydrolysis) to the cell is / are: A. The phosphorolysis reaction produces glucose-1-phosphate, which saves the cell one ATP molecule, whereas a hydrolysis reaction would have produced glucose. B.
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MCB 450 SU11_Exam III_KEY - Name:_NetID:_ Please print your...

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