Cells that respond to peptide hormones usually do so through a sequence of biochemical reactions involving receptor and kinase activation. In order for cells to respond, it is necessary for first and second messengers to communicate. This is possible because ________.
A) peptide hormones are converted by cell membranes enzymes into second messengers
B) hormones alter cellular operations through direct stimulation of a gene
C) G protein acts as the link between first and second messengers
D) the hormone receptor complex moves into the cytoplasm as a unit

Question

Quizplus · Accepted Answer

G proteins act as the link between first and second messengers by transmitting signals from the receptor to an effector molecule such as an enzyme or ion channel, leading to the conversion of the first messenger (the hormone) into a second messenger that initiates the cellular response. Choice A is incorrect because peptide hormones themselves act as first messengers, not second messengers. Choice B is incorrect because although hormones can stimulate gene expression, this does not occur through direct stimulation of a gene. Choice D is incorrect because while some hormone-receptor complexes can move into the cytoplasm, this is not necessary for the cell to respond to peptide hormones.

Cells That Respond to Peptide Hormones Usually Do So Through