Acid-base biochemistry: anion gap: 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 · Acid-base biochemistry: anion gap

Sample item

How is the plasma anion gap commonly calculated?

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

The answer and the reasoning

D. Sodium minus chloride minus bicarbonate

The conventional anion gap is calculated as sodium minus the sum of chloride and bicarbonate. It estimates unmeasured anions and helps classify metabolic acidosis.

Option by option

  • A. Bicarbonate minus sodium

    Bicarbonate minus sodium is not the formula.

  • B. Sodium plus potassium plus chloride

    Adding electrolytes does not estimate unmeasured anions.

  • C. Chloride minus albumin only

    Albumin influences the gap but does not replace the calculation.

  • D. Sodium minus chloride minus bicarbonate (correct)

    Correct. This is the standard simplified calculation.

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, Sodium minus chloride minus bicarbonate. The conventional anion gap is calculated as sodium minus the sum of chloride and bicarbonate.

Why is "Bicarbonate minus sodium" not the answer?

Bicarbonate minus sodium is not the formula.

Why is "Sodium plus potassium plus chloride" not the answer?

Adding electrolytes does not estimate unmeasured anions.

Why is "Chloride minus albumin only" not the answer?

Albumin influences the gap but does not replace the calculation.

What concept does this question test?

It tests Acid-base biochemistry: anion gap in Biochemistry. It estimates unmeasured anions and helps classify metabolic acidosis.

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 Acid-base biochemistry: anion gap?

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.