Respiratory physiology: oxygen dissociation curve: practice question

A Physiology 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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Physiology · Respiratory physiology: oxygen dissociation curve

Sample item

Which change shifts the oxyhaemoglobin dissociation curve to the right?

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

The answer and the reasoning

A. Increased 2,3-BPG

Increased 2,3-BPG lowers haemoglobin's oxygen affinity and shifts the curve right, aiding tissue unloading. Acidosis, hypercapnia and increased temperature do likewise.

Option by option

  • A. Increased 2,3-BPG (correct)

    Correct. 2,3-BPG stabilises deoxyhaemoglobin and promotes unloading.

  • B. Decreased temperature

    Lower temperature shifts the curve left.

  • C. Decreased PCO2

    Lower PCO2 causes a left shift through the Bohr effect.

  • D. Decreased hydrogen-ion concentration

    Lower hydrogen-ion concentration means alkalosis and a left shift.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Increased 2,3-BPG. Increased 2,3-BPG lowers haemoglobin's oxygen affinity and shifts the curve right, aiding tissue unloading.

Why is "Decreased temperature" not the answer?

Lower temperature shifts the curve left.

Why is "Decreased PCO2" not the answer?

Lower PCO2 causes a left shift through the Bohr effect.

Why is "Decreased hydrogen-ion concentration" not the answer?

Lower hydrogen-ion concentration means alkalosis and a left shift.

What concept does this question test?

It tests Respiratory physiology: oxygen dissociation curve in Physiology. Acidosis, hypercapnia and increased temperature do likewise.

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 Respiratory physiology: oxygen dissociation curve?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.