Glycolysis: pyruvate kinase deficiency: 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 · Glycolysis: pyruvate kinase deficiency

Sample item

A child has chronic non-spherocytic haemolytic anaemia, splenomegaly and a negative Coombs test. Red cell pyruvate kinase activity is low. Which finding is expected in these red cells?

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

The answer and the reasoning

D. Raised 2,3-bisphosphoglycerate with a rightward shift of the oxygen dissociation curve

Mature red cells depend on glycolysis for ATP. When pyruvate kinase is deficient, ATP falls, cells become rigid and are cleared by the spleen, while upstream intermediates including 2,3-bisphosphoglycerate accumulate. The raised 2,3-BPG shifts the curve to the right, so patients tolerate anaemia better than expected.

Option by option

  • A. Reduced NADPH with Heinz bodies as the main defect

    Low NADPH with Heinz bodies characterises G6PD deficiency, a pentose phosphate pathway defect.

  • B. Leftward shift of the oxygen dissociation curve

    A left shift would impair unloading, and the accumulating 2,3-BPG causes the opposite.

  • C. Raised ATP content with increased membrane deformability

    ATP is low in pyruvate kinase deficiency, so cells are rigid and not deformable.

  • D. Raised 2,3-bisphosphoglycerate with a rightward shift of the oxygen dissociation curve (correct)

    Proximal accumulation of 2,3-BPG shifts the curve right and improves oxygen unloading.

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, Raised 2,3-bisphosphoglycerate with a rightward shift of the oxygen dissociation curve. Mature red cells depend on glycolysis for ATP.

Why is "Reduced NADPH with Heinz bodies as the main defect" not the answer?

Low NADPH with Heinz bodies characterises G6PD deficiency, a pentose phosphate pathway defect.

Why is "Leftward shift of the oxygen dissociation curve" not the answer?

A left shift would impair unloading, and the accumulating 2,3-BPG causes the opposite.

Why is "Raised ATP content with increased membrane deformability" not the answer?

ATP is low in pyruvate kinase deficiency, so cells are rigid and not deformable.

What concept does this question test?

It tests Glycolysis: pyruvate kinase deficiency in Biochemistry. When pyruvate kinase is deficient, ATP falls, cells become rigid and are cleared by the spleen, while upstream intermediates including 2,3-bisphosphoglycerate accumulate. The raised 2,3-BPG shifts the curve to the right, so patients tolerate anaemia better than expected.

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 Glycolysis: pyruvate kinase deficiency?

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.