The acrosome reaction is an interaction between the acrosome of a spermatozoon and an egg that allows entry of the spermatozoon (see animation, right). The process is initiated when the receptors (red dots) on the spermatozoon come into contact with the jelly coat (orange) of the egg. This induces the acrosome reaction, which causes the acrosome to fuse with the plasma membrane of the spermatozoon. The actin (lavender) goes from a globular state to a filamentous state, pushing the front of the spermatozoon outward to form an elongated "acrosomal process." At the same time, the binding receptors (blue dots) are exposed and bind with the egg.
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