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清华大学本科生考试试题专用纸
考试课程
Biochemistry II
2004 年
10 月 26
日
1. Please finish this exam INDEPENDENTLY.
2. Please make your points clearly and concisely.
3. The score for each question is listed after each question.
4. The total score for this exam is 100.
5. Please hand in the finished exam on Nov. 2, 2004.
1. Pyruvate and ATP are the end products of glycolysis. In active muscle cells,
pyruvate is converted to lactate. Lactate is transported in the blood to the liver where
it is recycled by gluconeogenesis to glucose, which is transported back to muscle for
additional ATP production. Why don’t active muscle cells export pyruvate, which can
also be converted to glucose via gluconeogenesis? (10 points)
2. You and your fellow students find it difficult to believe that the oxidation of a
two-carbon acyl compound requires a pathway as complex as the citric acid cycle. In
order to verify the metabolic pathways you have been learning about, you conduct an
experiment using a sample of glucose radioactively labeled with 14C at C-1. If the
information you have learned is correct, in which glycolytic or citric acid cycle
intermediate, and on which carbon, should you find the label:
(a) if O2 was unavailable? (10 points)
(b) in the presence of malonate? (10 points)
(c) after one round of the citric acid cycle? (10 points)
(d) after three rounds of the citric acid cycle? (10 points)
3. Some amino acids can be converted to ketone bodies.
(a) List those ketogenic amino acids. (5 points)
(b) Why are these amino acids especially important under conditions of starvation or
untreated diabetes? (10 points)
(c) Which reaction pathway converts the carbon skeleton of alanine to a ketone body?
(5 points)
4. Suppose you are stranded on a desert island and have nothing but protein to eat.
Outline briefly how your body will use this source of food for its energy needs.
(10 points)
5. Oxidative phosphorylation and photophosphorylation resemble each other in
certain respects. Describe the ways in which the two processes are similar, and
then list the significant differences. (20 points)