Question

When a ligand binds to a G protein-linked receptor, the G protein ____

(A) is activated
(B) hydrolyzes GDP
(C) binds to a signal molecule
(D) releases a hormone

Answer 1

The correct answer is (A) is activated

Step-by-step explanation:

GPCR is a serpentine receptor found in eukaryotes containing seven trans membrane protein. When any ligand binds to GPCR outside the cell it activates the G protein and cause conformational changes in transmembrane protein receptor.

This conformational change activates a signaling pathway in which GDP bound to G-protein(α subunit) is exchanged by GTP and then dissociate from βΥ subunit to complete the signaling process.

So the correct answer is (A) is activated

Answer 2

The correct answer is option A, that is, is activated.

Step-by-step explanation:

The GPCRs or the G protein-coupled receptors contain a huge family of receptors, which determine molecules outside the cell and stimulate internal signal transduction pathways, and eventually, the cellular responses. The GPCRs are found in eukaryotes like choanoflagellates, yeast, and animals.

The ligands, which combine and stimulate these receptors comprise odors, light-sensitive compounds, hormones, pheromones, and neurotransmitters. With the binding of a ligand to the GPCR, a conformational change occurs in the GPCR that permits it to function as GEF or guanine nucleotide exchange factor. The GPCR can then stimulate an associated G protein by interchanging the GDP bound to the G protein for a GTP.