Which molecule is a first messenger but not a second messenger?
A) G protein
B) cyclic AMP
C) acetylcholine
D) protein kinase
E) adenylyl cyclase

Question

Quizplus · Accepted Answer

Acetylcholine is a neurotransmitter that acts as a first messenger by binding to receptors on the cell surface, initiating a signaling cascade. It does not act as a second messenger, which are intracellular signaling molecules.

Which Molecule Is a First Messenger but Not a Second