BIOL 443 Lecture Notes - Lecture 8: Polyspermy, Lipid Bilayer Fusion, Acrosome Reaction
Document Summary
In sea urchins disrupting the membrane potential can either block fertilization (if made positive) or cause polyspermy (if formed to be kept negative: the fast block to polyspermy is a change in membrane potential: -70mv to. Accomplished in sea urchins by opening of sodium channels, allowing sodium to briefly rush into the cells. Most likely acts by blocking positively-charged fusogenic proteins from promoting membrane fusion. Does not seem to occur in mammals: the slow block to polyspermy is required after membrane potential is normalized (about a minute after fertilization) Must remove sperm bound to the vitelline envelope by this time. Mediated by the fusion of the cortical granules with the egg cell membrane: the contents of the cortical granules bind to the vitelline envelope to form the fertilization envelope. Glycosaminoglycans (mucopolysaccharides) absorb water and move the envelope away from the egg. In mouse, the egg centriole is used instead.
