試題詳解

36. About intracellular signaling, which of the following descriptions is correct?
(A) Guanine nucleotide-exchange factors (GEFs) switch the GTPases to GTP-bound forms and inactivate them, whereas GTPases-activating proteins (GAPs) switch the GTPases to GDP-bound states and activate them.
(B) Calcium serves as an important second messenger, and the intracellular calcium is primarily stored in endoplasmic reticulum (ER) and the Golgi.
(C) Upon activation of G protein-coupled receptors (GPCR), the Ga subunit of G protein dissociates from the receptors and binds to downstream effectors to activate the signaling cascades.
(D) GPCR is one of the largest protein families in the genome of metazoan species.
(E) GPCRs regulate cAMP- or phospholipase C (PLC)-based signaling pathways, but they do not regulate ion channels.