Practice question

Cortical reaction represents slow block to polyspermy activated by fertilization calcium wave propagating across egg. Calcium binds synaptotagmin on cortical granules docked beneath plasma membrane triggering SNARE-mediated fusion and exocytosis. Contents including proteases, sulfated glycosaminoglycans, hyalin, ovoperoxidase, and transglutaminase are released into perivitelline space. Enzymes cleave vitelline envelope attachments, separate it from plasma membrane, osmotically expand space, and modify it into hardened fertilization envelope. This elevation completes in about minute after fast electrical block based on depolarization, providing permanent mechanical barrier preventing additional sperm entry and protecting embryo from environmental damage.