When a sperm cell enters an egg, no other sperm cell can enter because the egg produces a?
The cortical reaction, also known as the zona reaction, occurs when a sperm cell unites with the egg’s plasma membrane, altering the zona pellucida which prevents other sperm from binding to and entering the egg. The cortical reaction is exocytosis of the egg’s cortical granules. Cortical granules are secretory vesicles that reside just below the egg’s plasma membrane. When the fertilizing sperm contacts the egg plasma membrane, it causes calcium to be released from storage sites in the egg, raising the intracellular free calcium concentration. This triggers fusion of the cortical granule membranes with the egg plasma membrane, liberating the contents of the granules to the extracellular space.
