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 enzyme of the TCA cycle is directly inhibited by fluoroacetate toxicity through formation of fluorocitrate?

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

The answer and the reasoning

B. Aconitase

Fluoroacetate is converted to fluorocitrate, which inhibits aconitase and disrupts the TCA cycle. Citrate accumulation and impaired energy production result.

Option by option

  • A. Malate dehydrogenase

    Malate dehydrogenase interconverts malate and oxaloacetate.

  • B. Aconitase (correct)

    Correct. Aconitase is the fluorocitrate-sensitive enzyme.

  • C. Citrate synthase

    Citrate synthase forms citrate from acetyl-CoA and oxaloacetate.

  • D. Succinate thiokinase

    Succinate thiokinase generates GTP from succinyl-CoA.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Aconitase. Fluoroacetate is converted to fluorocitrate, which inhibits aconitase and disrupts the TCA cycle.

Why is "Malate dehydrogenase" not the answer?

Malate dehydrogenase interconverts malate and oxaloacetate.

Why is "Citrate synthase" not the answer?

Citrate synthase forms citrate from acetyl-CoA and oxaloacetate.

Why is "Succinate thiokinase" not the answer?

Succinate thiokinase generates GTP from succinyl-CoA.

What concept does this question test?

It tests TCA cycle in Biochemistry. Citrate accumulation and impaired energy production result.

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.