Practice question

Following fertilization calcium transient, sea urchin eggs increase oxygen consumption several-fold within minutes, termed respiratory burst. Calcium activates NADPH-dependent oxidase complex in cortex producing superoxide converted to hydrogen peroxide. Hydrogen peroxide serves as substrate for ovoperoxidase released from cortical granules to catalyze di-tyrosine cross-links hardening fertilization envelope. Burst is calcium dependent, inhibited by calcium chelators BAPTA, and occurs concurrently with envelope elevation and cortical reaction. It parallels NADPH oxidase activity in phagocytes but here functions developmentally for extracellular matrix stabilization rather than pathogen killing, not for immediate ATP synthesis or meiotic regulation.