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Signal transduction pathways Transitional Reasoning Practice

Biology · Cell Communication & the Cell Cycle · Biology · Cell Communication

1 Biology practice questions on Signal transduction pathways. Questions that build towards applied reasoning.

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  1. 1.

    In liver cells, glucagon binds to a G protein-coupled receptor to activate adenylyl cyclase, which converts ATP into cyclic AMP (cAMP) and subsequently activates protein kinase A to stimulate glycogen breakdown. Phosphodiesterase normally hydrolyzes cAMP into AMP to terminate this intracellular signal. If liver cells are pretreated with a chemical inhibitor that selectively blocks phosphodiesterase before receiving a brief pulse of glucagon, which outcome will most directly occur?

    • A) Prolonged activation of protein kinase A and sustained glucose release compared to untreated cells
    • B) Immediate failure of the G protein to exchange GDP for GTP upon receptor activation
    • C) Complete inhibition of adenylyl cyclase due to rapid depletion of intracellular ATP
    • D) Permanent binding of glucagon to the extracellular domain of the transmembrane receptor

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