Metabolism: ethanol: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Metabolism: ethanol

Sample item

A chronic alcohol drinker is found after a binge without food, with hypoglycaemia and lactic acidosis. What best explains the hypoglycaemia?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. High NADH/NAD+ ratio diverting pyruvate to lactate and oxaloacetate to malate, impairing gluconeogenesis

Oxidation of ethanol by alcohol and aldehyde dehydrogenase generates large amounts of NADH. The excess NADH converts pyruvate to lactate and oxaloacetate to malate, depleting substrates for gluconeogenesis when glycogen stores are low, and this causes fasting hypoglycaemia and lactic acidosis.

Option by option

  • A. Conversion of acetyl-CoA from fatty acid oxidation into glucose

    Humans cannot convert acetyl-CoA into glucose, because pyruvate dehydrogenase is irreversible.

  • B. Absence of hepatic glucose-6-phosphatase

    Glucose-6-phosphatase is present in the liver, and its absence causes von Gierke disease, a genetic disorder.

  • C. Direct stimulation of insulin release by acetaldehyde

    Hypoglycaemia in alcoholics is due to impaired glucose production, not insulin excess driven by acetaldehyde.

  • D. High NADH/NAD+ ratio diverting pyruvate to lactate and oxaloacetate to malate, impairing gluconeogenesis (correct)

    Correct. A high NADH/NAD+ ratio diverts gluconeogenic precursors and blocks glucose production.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, High NADH/NAD+ ratio diverting pyruvate to lactate and oxaloacetate to malate, impairing gluconeogenesis. Oxidation of ethanol by alcohol and aldehyde dehydrogenase generates large amounts of NADH.

Why is "Conversion of acetyl-CoA from fatty acid oxidation into glucose" not the answer?

Humans cannot convert acetyl-CoA into glucose, because pyruvate dehydrogenase is irreversible.

Why is "Absence of hepatic glucose-6-phosphatase" not the answer?

Glucose-6-phosphatase is present in the liver, and its absence causes von Gierke disease, a genetic disorder.

Why is "Direct stimulation of insulin release by acetaldehyde" not the answer?

Hypoglycaemia in alcoholics is due to impaired glucose production, not insulin excess driven by acetaldehyde.

What concept does this question test?

It tests Metabolism: ethanol in Biochemistry. The excess NADH converts pyruvate to lactate and oxaloacetate to malate, depleting substrates for gluconeogenesis when glycogen stores are low, and this causes fasting hypoglycaemia and lactic acidosis.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Metabolism: ethanol?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.