The link between a first messenger and a second messenger in a cell that responds to peptide hormones is usually
A)cAMP.
B)cGMP.
C)ATP.
D)a G protein.
E)calcium ion levels.

Question

Quizplus · Accepted Answer

The link between a first messenger and a second messenger in a cell that responds to peptide hormones is usually a G protein. Peptide hormones cannot diffuse through the plasma membrane of target cells and must bind to cell surface receptors. These receptors activate G proteins inside the cell, which in turn activate or inhibit effector molecules such as adenylyl cyclase, ultimately leading to the production of the secondary messenger cAMP.

The Link Between a First Messenger and a Second Messenger