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

Question

Quizplus · Accepted Answer

The link between a first messenger (the peptide hormone) and a second messenger in a cell that responds to peptide hormones is usually a G protein. G proteins are activated by the binding of the hormone to a receptor on the cell surface, which leads to a series of intracellular events that ultimately result in the activation or inhibition of various cellular processes.

Answer: A
 The second messenger in this pathway is usually cAMP. When a hormone binds to its receptor on the cell surface, it often activates a G protein, which in turn activates an enzyme called adenylate cyclase. Adenylate cyclase then converts ATP to cAMP, which can then activate other enzymes and signaling pathways within the cell.

The Link Between a First Messenger and a Second Messenger