Final answer:
The sperm head binds to ZP₃ glycoprotein within the zona pellucida, which is essential for sperm to penetrate the oocyte and achieve fertilization.
Step-by-step explanation:
The sperm head binds to ZP₃ glycoprotein within the zona pellucida, a thick, gel-like membrane that coats the oocyte and must be penetrated by sperm for fertilization to occur. When the capacitated sperm encounters the oocyte, an acrosomal reaction is initiated as the sperm bind to specific receptors on the zona pellucida. This reaction involves the release of digestive enzymes from the acrosome of the sperm, facilitating a pathway through the zona pellucida, allowing the sperm to reach the oocyte. Ultimately, a single sperm fuses with the oocyte, with its head and mid-piece entering the oocyte to conclude fertilization.