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Biochemistry

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Carbohydrates

Question
69 out of 78
 

After alcohol ingestion, which of the following intermediates accumulates in liver that is not typical of glycolysis or the citric acid cycle ?



A Acetyls-CoA
B Lactate

C Acetaldehyde
D Citrate

Ans. C Acetaldehyde

a. During alcohol ingestion by humans, liver alcohol dehydrogenase converts ethanol to acetaldehyde. The acetaldehyde can be metabolized to acetate by acetaldehyde dehydrogenase and then to acetyl-CoA.

b. The alcohol and acetaldehyde dehydrogenases both generate NADH, increasing the NADH / NAD ratio and stimulating lipid synthesis.

c. The increased lipid synthesis with chronic ethanol ingestion contributes to the fatty liver of alcoholism. In normal glycolysis, three- carbon metabolites such as glyceraldehyde are metabolized to pyruvate.

d. In the liver and in resting muscle, almost all pyruvate produced is converted to acetyl-CoA for oxidation in the citric acid cycle. In actively contracting muscle, when oxygen is limited, lactate accumulates.

e. No acetate is converted to acetaldehyde since the acetaldehyde dehydrogenase is irreversible. This reverse pathway is utilized by yeast to produce ethanol during fermentation of grapes or other plant products. Yeast converts pyruvate to acetaldehyde and then acetaldehyde to ethanol.

Carbohydrates Flashcard List

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