Map hninger Principles of Biochemistry lson | Cox SEVENTH EDITION MHE/Freeman by
ID: 196333 • Letter: M
Question
Map hninger Principles of Biochemistry lson | Cox SEVENTH EDITION MHE/Freeman by Sapling Leaning The consumption of alcohol (ethanol), especially after periods of strenuous activity or after not eating for several hours, results in a deficiency of glucose in the blood, a condition known as hypoglycemia. The first step in the metabolism of ethanol by the liver is oxidation to acetaldehyde, catalyzed by liver alcohol dehydrogenase CH3CH2OH + NAD+ CH3CHO + NADH + H+ How does this reaction inhibit the transformation of lactate to pyruvate and lead to hypoglycemia? The conversion of lactate to glucose in the liver is inhibited. The metabolism of both ethanol and lactate requires the same oxidizing agent. The conversion of lactate to glucose in the muscle is inhibited. NADH slows the conversion of pyruvate to lactate by lactate dehydrogenase. The NADH produced in the liver is depleted during ethanol fermentation. Incorrect. At least one of your choices is incorrect. Both ethanol and lactate are oxidized in the liver. Think about the identity of the oxidizing agent. Also think about how blood glucose is produced during starvation or periods of strenuous activityExplanation / Answer
The first step in the synthesis of glucose from lactate in the liver is oxidation of the lactate to pyruvate; like the oxidation of ethanol to acetaldehyde, this requires NAD+. With-consumption of alcohol forces a competition for NAD+ between ethanol metabolism and gluconeogenesis, reducing the conversion of lactate to glucose and resulting in hypoglycemia. The problem is compounded by strenuous exercise and lack of food because at these times the level of blood glucose is already low.