Respiratory: 2,3-BPG and stored blood: 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: 2,3-BPG and stored blood

Sample item

A patient receives massive transfusion of red cells stored for 3 weeks in a blood bank. How is oxygen delivery to tissues initially affected through the haemoglobin dissociation curve?

AThe curve is unchanged because stored cells contain normal 2,3-BPGBRaised carbon dioxide shifts the curve to the right, increasing deliveryCDepleted 2,3-BPG shifts the curve to the left, so haemoglobin holds oxygen more tightly and delivers less to tissuesDRaised 2,3-BPG shifts the curve to the right, increasing delivery

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

The answer and the reasoning

C. Depleted 2,3-BPG shifts the curve to the left, so haemoglobin holds oxygen more tightly and delivers less to tissues

2,3-BPG binds deoxyhaemoglobin and lowers its oxygen affinity, shifting the curve to the right. Red cells in stored blood lose 2,3-BPG over days, so P50 falls, the curve shifts left and release of oxygen to tissues is reduced until 2,3-BPG is regenerated within about 24 hours in the recipient.

Option by option

A. The curve is unchanged because stored cells contain normal 2,3-BPG
Stored red cells are depleted of 2,3-BPG, so it is not normal.
B. Raised carbon dioxide shifts the curve to the right, increasing delivery
Carbon dioxide does not accumulate in a way that is relevant, and the stored cell problem is 2,3-BPG depletion.
C. Depleted 2,3-BPG shifts the curve to the left, so haemoglobin holds oxygen more tightly and delivers less to tissues (correct)
Correct. Loss of 2,3-BPG raises oxygen affinity.
D. Raised 2,3-BPG shifts the curve to the right, increasing delivery
Stored cells lose 2,3-BPG rather than gain it.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Depleted 2,3-BPG shifts the curve to the left, so haemoglobin holds oxygen more tightly and delivers less to tissues. 2,3-BPG binds deoxyhaemoglobin and lowers its oxygen affinity, shifting the curve to the right.

Why is "The curve is unchanged because stored cells contain normal 2,3-BPG" not the answer?

Stored red cells are depleted of 2,3-BPG, so it is not normal.

Why is "Raised carbon dioxide shifts the curve to the right, increasing deliv…" not the answer?

Carbon dioxide does not accumulate in a way that is relevant, and the stored cell problem is 2,3-BPG depletion.

Why is "Raised 2,3-BPG shifts the curve to the right, increasing delivery" not the answer?

Stored cells lose 2,3-BPG rather than gain it.

What concept does this question test?

It tests Respiratory: 2,3-BPG and stored blood in Physiology. Red cells in stored blood lose 2,3-BPG over days, so P50 falls, the curve shifts left and release of oxygen to tissues is reduced until 2,3-BPG is regenerated within about 24 hours in the recipient.

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: 2,3-BPG and stored blood?

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.