Practice question

Cortical granules discharge heterogeneous mixture; glycosaminoglycans such as chondroitin sulfate proteoglycans are major osmotically active component. Upon release into narrow perivitelline space they rapidly hydrate and swell, generating high colloid osmotic pressure drawing water between vitelline envelope and plasma membrane. Resulting influx expands space beneath envelope lifting it outward to create perivitelline space and nascent fertilization envelope. Hardening occurs later via ovoperoxidase-mediated dityrosine crosslinking, while receptor removal depends on protease cleavage. Glycosaminoglycans do not harden envelope, digest receptors, or induce acrosomal exocytosis; their physical swelling provides elevating force essential for block.