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Second messengers Transitional Reasoning Practice

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

1 Biology practice questions on Second messengers. Questions that build towards applied reasoning.

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  1. 1.

    A researcher studies how a water-soluble peptide hormone stimulates glycogen breakdown in liver cells. When the hormone is microinjected directly into the cytoplasm, no glycogen breakdown occurs, but extracellular application induces a rapid cytoplasmic surge of cyclic AMP (cAMP) followed by target enzyme activation. Furthermore, introducing cAMP directly into an isolated, cell-free cytoplasmic preparation triggers immediate glycogen breakdown, whereas introducing the peptide hormone alone has no effect. Based on these observations, which conclusion best explains the role of cAMP in this pathway?

    • A) Cyclic AMP diffuses outside the cell to initiate transcription of peptide hormone receptor genes.
    • B) Cyclic AMP acts as an intracellular relay molecule that propagates the signal initiated by the extracellular hormone.
    • C) The peptide hormone directly enters the cytoplasm once cAMP alters the fluidity of the plasma membrane.
    • D) Cyclic AMP functions as the primary ligand that physically opens extracellular membrane transport channels.

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