AP BIOLOGY

Detailed explanation-1: -G Protein Coupled Receptors (GPCRs) perceive many extracellular signals and transduce them to heterotrimeric G proteins, which further transduce these signals intracellular to appropriate downstream effectors and thereby play an important role in various signaling pathways.

Detailed explanation-2: -G proteins regulate metabolic enzymes, ion channels, transporter proteins, and other parts of the cell machinery, controlling transcription, motility, contractility, and secretion, which in turn regulate diverse systemic functions such as embryonic development, learning and memory, and homeostasis.

Detailed explanation-3: -Mutant G proteins Indeed, GNAS is mutated in 4.4% of the 9, 486 tumor sequences deposited to date in the COSMIC database, making it one of the most frequently mutated G proteins in human cancer (Table 1).

Detailed explanation-4: -The main physiological functions of G-proteins are to relay the signals from GPCRs which function as GEFs for G-proteins. Binding with exogenous or endogenous agonists induces GPCRs into an active conformational state which, in turn, influences intracellular binding of G-proteins or arrestin proteins [23, 24].