Practice question

Freshly ejaculated sperm are coated with cholesterol, glycoproteins and seminal plasma decapacitation factors stabilizing membrane preventing premature acrosome reaction. During capacitation within female tract, albumin and high-density lipoproteins act as sinks extracting cholesterol from plasma membrane, increasing fluidity and permeability, displacing SPINK proteins. Cholesterol removal alters lipid rafts, triggers adenylate cyclase activation, calcium permeability increase and tyrosine phosphorylation cascades. Membrane becomes fusogenic, receptors unmasked for zona binding. Cholesterol efflux therefore represents initiating step unlocking fertilizing potential, capacitation-associated signaling competence, acrosome responsiveness and fertilization readiness for conception.