Practice question

After initial elevation triggered by mucopolysaccharide swelling, vitelline envelope transformed into fertilization envelope requires chemical hardening to provide durable mechanical barrier against supersperm and environmental stress. Two cortical granule enzymes accomplish covalent stabilization: egg-specific ovoperoxidase catalyzes oxidative crosslinking forming dityrosine bridges between adjacent envelope glycoproteins using hydrogen peroxide, while transglutaminase catalyzes formation of ε-(γ-glutamyl)lysine isopeptide bonds. Together these enzymatic crosslinks convert soluble vitelline envelope into insoluble, tough, impermeable protective coat encasing embryo. Glycosaminoglycans drive swelling but not stabilization, hyalin builds hyaline layer for cell adhesion, Na+ mediates fast electrical block. Thus stabilization depends on peroxidase-transglutaminase system.