Practice question

Molecular cloning of bindin receptor revealed EBR1 glycoprotein complex not localized on plasma membrane but embedded within vitelline envelope surrounding egg. Receptor evolved as extracellular matrix component providing docking platform for acrosomal process containing bindin after penetrating jelly. Upon bindin-EBR1 adhesion, sperm becomes tethered, allowing subsequent lipid bilayer fusion lateral to bound site rather than directly at receptor cluster. Only after secure binding does sperm plasma membrane merge with egg membrane. Cortical granules, jelly and cortical cytoplasm lack primary bindin receptor; vitelline envelope serves exclusive scaffold for species-specific gamete adhesion.