The evolution of signaling molecules has made it possible for cells of multicellular organisms, such as humans, to communicate with one another in simple and complex ways. Signaling molecules may be used to transmit information between cells (extracellular or intercellular signaling), or they may be involved in signaling cascades inside cells (cytoplasmic or intracellular signaling). Test your basic knowledge of signaling molecules by taking this simple quiz.
(1) Many hormones exert their influence on target cells by binding to G protein-coupled receptors (GPCR) that are coupled to cytoplasmic G proteins. G proteins are composed of the following subunits:
(2) When activated, this G protein subunit leads to the elevation of cytoplasmic cAMP levels.
(3) When activated, this G protein subunit leads to a decrease in cytoplasmic cAMP levels.
(4) The enzyme adenylate cyclase (also referred to as adenylyl cyclase) is stimulated by this G protein.
(5) The enzyme adenylate cyclase (also referred to as adenylyl cyclase) is inhibited by this G protein.