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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.

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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.

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General physiology MCQ (B11-PHYS3-3)

Q: What is the answer to this Physiology question?

The best answer is C, Autophosphorylation of tyrosine residues of the receptor beta subunits, which recruits insulin receptor substrate proteins. The insulin receptor is a receptor tyrosine kinase; ligand binding causes autophosphorylation of the intracellular beta subunits.

Q: What concept does this question test?

It tests General physiology: insulin receptor signalling in Physiology. The phosphotyrosines recruit insulin receptor substrates, which activate PI3 kinase and Akt and finally drive GLUT4 translocation. Growth factor receptors use the same type of receptor tyrosine kinase signalling.

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Physiology · General physiology: insulin receptor signalling

Sample item

In a skeletal muscle cell, insulin increases glucose uptake by promoting GLUT4 insertion into the plasma membrane. Which initial signalling step follows insulin binding to its receptor?

ADirect conversion of GTP to cyclic GMP by the receptor's guanylyl cyclase domainBRecruitment of JAK2 associated with the receptor, which phosphorylates STAT proteinsCAutophosphorylation of tyrosine residues of the receptor beta subunits, which recruits insulin receptor substrate proteinsDActivation of a stimulatory G protein that raises cyclic AMP

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

The answer and the reasoning

C. Autophosphorylation of tyrosine residues of the receptor beta subunits, which recruits insulin receptor substrate proteins

The insulin receptor is a receptor tyrosine kinase; ligand binding causes autophosphorylation of the intracellular beta subunits. The phosphotyrosines recruit insulin receptor substrates, which activate PI3 kinase and Akt and finally drive GLUT4 translocation. Growth factor receptors use the same type of receptor tyrosine kinase signalling.

Option by option

A. Direct conversion of GTP to cyclic GMP by the receptor's guanylyl cyclase domain
Intrinsic guanylyl cyclase is the mechanism of atrial natriuretic peptide receptors, not insulin.
B. Recruitment of JAK2 associated with the receptor, which phosphorylates STAT proteins
JAK-STAT signalling is used by growth hormone and prolactin receptors, which lack intrinsic kinase activity.
C. Autophosphorylation of tyrosine residues of the receptor beta subunits, which recruits insulin receptor substrate proteins (correct)
Correct. Intrinsic tyrosine kinase activity starts the cascade.
D. Activation of a stimulatory G protein that raises cyclic AMP
The insulin receptor is not G protein coupled, and cAMP is the messenger for glucagon and catecholamines.

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.

General physiology: insulin receptor signalling: practice question

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The answer and the reasoning

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