Carbohydrate metabolism: glucagon: 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 · Carbohydrate metabolism: glucagon

Sample item

During a prolonged fast, glucagon acts on the liver mainly by:

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

The answer and the reasoning

C. Raising cyclic AMP and activating protein kinase A, which stimulates glycogenolysis and gluconeogenesis

Glucagon binds a Gs-coupled receptor, raising cAMP and activating protein kinase A. This activates phosphorylase kinase and glycogen phosphorylase, inactivates glycogen synthase, lowers fructose-2,6-bisphosphate (favouring gluconeogenesis) and induces gluconeogenic enzymes.

Option by option

  • A. Activating the insulin receptor tyrosine kinase

    The insulin receptor is a tyrosine kinase activated by insulin only.

  • B. Stimulating glycolysis by raising fructose-2,6-bisphosphate

    Glucagon lowers fructose-2,6-bisphosphate, which reduces glycolysis and favours gluconeogenesis.

  • C. Raising cyclic AMP and activating protein kinase A, which stimulates glycogenolysis and gluconeogenesis (correct)

    Correct. The cAMP-protein kinase A pathway promotes glucose output.

  • D. Raising cyclic GMP to stimulate glycogen synthesis

    Glycogen synthesis is favoured by insulin, not glucagon.

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 C, Raising cyclic AMP and activating protein kinase A, which stimulates glycogenolysis and gluconeogenesis. Glucagon binds a Gs-coupled receptor, raising cAMP and activating protein kinase A.

Why is "Activating the insulin receptor tyrosine kinase" not the answer?

The insulin receptor is a tyrosine kinase activated by insulin only.

Why is "Stimulating glycolysis by raising fructose-2,6-bisphosphate" not the answer?

Glucagon lowers fructose-2,6-bisphosphate, which reduces glycolysis and favours gluconeogenesis.

Why is "Raising cyclic GMP to stimulate glycogen synthesis" not the answer?

Glycogen synthesis is favoured by insulin, not glucagon.

What concept does this question test?

It tests Carbohydrate metabolism: glucagon in Biochemistry. This activates phosphorylase kinase and glycogen phosphorylase, inactivates glycogen synthase, lowers fructose-2,6-bisphosphate (favouring gluconeogenesis) and induces gluconeogenic enzymes.

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 Carbohydrate metabolism: glucagon?

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.