Final answer:
Sperm are guided by chemical attractants released by the cells of the corona radiata. They must penetrate protective layers and use digestive enzymes to reach the oocyte. Fusion with the oocyte's plasma membrane allows the genetic material to enter.
Step-by-step explanation:
Sperm are guided toward an egg cell (ovum) by changes in the chemical attractants released by the cells of the corona radiata. These attractants cause the sperm to stream toward the oocyte. Once the sperm reach the oocyte, they must penetrate the protective layers, including the zona pellucida.
The sperm bind to receptors in the zona pellucida, triggering the release of digestive enzymes from the acrosome. These enzymes clear a path through the zona pellucida, allowing the sperm to reach the oocyte.
Finally, a single sperm makes contact with sperm-binding receptors on the oocyte's plasma membrane and fuses with it, allowing the genetic material to enter the oocyte.