TCA cycle: 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 · TCA cycle

Sample item

Which molecule enters TCA cycle by combining with oxaloacetate?

ALactateBGlucoseCPyruvate onlyDAcetyl-CoA

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

The answer and the reasoning

D. Acetyl-CoA

This item reviews TCA cycle; Acetyl-CoA is the best answer because it directly matches the biochemical or pathological mechanism described.

Option by option

A. Lactate
Lactate is plausible but not the best answer.
B. Glucose
Glucose is unsupported by the key feature.
C. Pyruvate only
Pyruvate only does not fit the stated pattern.
D. Acetyl-CoA (correct)
Correct. Acetyl-CoA fits the defining mechanism.

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.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Acetyl-CoA. This item reviews TCA cycle; Acetyl-CoA is the best answer because it directly matches the biochemical or pathological mechanism described.

Why is "Lactate" not the answer?

Lactate is plausible but not the best answer.

Why is "Glucose" not the answer?

Glucose is unsupported by the key feature.

Why is "Pyruvate only" not the answer?

Pyruvate only does not fit the stated pattern.

What concept does this question test?

It tests TCA cycle in Biochemistry. The correct option holds because: Correct. Acetyl-CoA fits the defining mechanism.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 TCA cycle?

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.