PPT Slide
1. Receptor glycoprotein in sperm Plasma Membrane contacts polysaccharide in jelly coat (SU) or glycoprotein in zona pellucida (mammals). This causes Na+ channels in the PM to open.
2. Na+ ions flow into sperm head and the PM depolarizes, opening voltage-sensitive Ca++ channels. Ca++ ions flow into the sperm head.
3. Ca++ causes the the fusion of the AV with the PM, releasing AV contents into the extracellular space. Digestive enzymes from the AV digest the jelly coat and vitelline membrane (SU) or ZP (mammals). A Na+:H+ ion exchanger in the PM is activated, pumping H+ out of the cell, increasing intracellular pH.
4. This pH change causes the polymerization of actin subunits into microfilament cables that thrust Acrosomal Processes toward egg PM’s. Bindin released from the AV coats the acrosomal process (SU). The increase in intracellular [ion] causes H2O to enter the cell, increasing hydrostatic pressure. This aids in the extension of the AP.