Biochemistry Sample Questions

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Part 1: (30 questions; 2 points each; 60 points) Answer the first group of questions on your Scantron form. Be sure to align the question number with the Scantron answer bubble! No part credit will be given in this part. Part II (65 points) Answer these questions in your blue book. Indicate clearly which question your work supports. Partial credit may be given when work is clearly shown and when answers are explained. 1. (10 points) Carbohydrates a) Draw a Haworth projection of the disaccharide lactose. Deficiency of the enzyme lactase (common in adult mammals) prevents cleavage of the glycosidic link in lactose during digestion. Instead, anaerobic bacteria in the large intestine ferment this sugar, producing gas, abdominal discomfort and bloating. What gas is formed and what metabolic byproduct(s) also are released into the large intestine? b) Briefly describe the differences between the polysaccharides….. i) amylopectin and glycogen ii) amylose and chitin 2. (10 points) The catabolic cycle called glycolysis is the most universal energy-producing metabolic pathway for organisms that live on or near the earth’s surface. a) Stage I glycolysis actually consumes ATP. In which steps is ATP converted to ADP and how is the phosphate group used? b) Stage II glycolysis produces some ATP directly and also reduced NADH. How are these electron carriers reoxidized in anaerobic bacteria? How are these electron carriers reoxidized in aerobic bacteria? 3. (24 points) Aerobic eukaryotic organisms use the unique abilities of mitochondria to extract further energy from glucose (and other nutrients). a) The citric acid cycle completes the degradation of glucose. Give specific structural formulas for the reactants and products of each step and name the associated enzymes. Are these processes oxidative or reductive overall for the carbon

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