Insulin binds to its receptor and activates downstream glucose uptake. The IMMEDIATE biochemical consequence of insulin binding to its receptor tyrosine kinase is:

• A Activation of adenylyl cyclase and cAMP production
• B Direct activation of GLUT4 by receptor-mediated phosphorylation
• C Activation of protein kinase A through cAMP-independent mechanism
• D Receptor autophosphorylation on tyrosine residues in the cytoplasmic domain ✓

Explanation

The insulin receptor is a heterotetrameric tyrosine kinase (alpha2-beta2). Insulin binding to the alpha subunits triggers trans-autophosphorylation of tyrosine residues on the beta subunits' cytoplasmic domains, which then recruit IRS-1/IRS-2 via SH2 domains, initiating PI3K-Akt-mTOR cascade — ultimately causing GLUT4 vesicle translocation. Adenylyl cyclase and PKA are activated by glucagon (Gs pathway), not insulin.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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