After the sperm have been ejaculated into the female reproductive tract, they must undergo two processes in order to be capable of fertilizing the egg.
The first process that the sperm must undergo is sperm capacitation. Capacitation is the process that requires the removal or modification of molecules associated with the sperm head (Jones and Lopez, 2006). The molecules that are on the head of the sperm are glycoproteins. The function of these glycoproteins is to help stabilize the plasma membrane of the sperm and suppress the ability of the sperm to fertilize the egg (Jones and Lopez, 2006). Once these glycoproteins have been removed, the sperm are able to respond to various signals in the female reproductive tract. A result of capacitation is an increase in the movement of their tails which allows quicker movement to the ovulated egg. This capacitation also allows the sperm to undergo the acrosomal reaction.
The second process that the sperm must undergo is sperm activation. Activation occurs during the acrosomal reaction. During this reaction the plasma membrane of the oocyte fuses with the outer acrosomal membrane of the sperm (Jones and Lopez, 2006). The areas where these two membranes fuse will form a composite membrane. This composite membrane helps form breaks which allows the enzymes in the acrosomal membrane of the sperm head to be released.