Binding of sperm to egg,”1. Contact:The sperm cell contacts the egg’s jelly coat, Triggering ocytosis from the sperm’s acrosome.2. The acrosomal reaction: Hydrolytic enzymes released from the acrosome make a hole in the jelly coat, while growing actin filaments form the acrosomal process. This structure protrudes from the sperm head and penetrates the jelly coat, binding to receptors in the egg cell membrane that extend through the vitelline layer.3. depolarization (fast block to polyspermy):Contact and fusion of sperm and egg membranes. A hole is made in the vitelline layer, allowing contact and fusion of the gamete plasma membranes. The membrane becomes depolarized, resulting in the fast block to polyspermy.4. Entry of sperm nucleus5. Increased intracellular calcium level:Cortical reaction. Fusion of the gamete membranes triggers an increase of Ca2+ in the egg’s cytosol, causing cortical granules in the egg to fuse with the plasma membrane and discharge their contents. This leads to swelling of the perivitelline space, hardening of thevitelline layer, and clipping of sperm-binding receptors. The resulting fertilization envelope is the slow block to polyspermy.6. Formation of fertilization envelope:vitelline layer

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