AP BIOLOGY

Detailed explanation-1: -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].

Detailed explanation-2: -Some examples of GPCRs include beta-adrenergic receptors, which bind epinephrine; prostaglandin E2 receptors, which bind inflammatory substances called prostaglandins; and rhodopsin, which contains a photoreactive chemical called retinal that responds to light signals received by rod cells in the eye.

Detailed explanation-3: -The G protein transports hormones across the plasma membrane.

Detailed explanation-4: -G protein activation leads to activation of various second messenger systems and intracellular responses, leading to physiological responses of tissues and organisms. In the inactive heterotrimeric state, GDP is bound to the G subunit.