Sperm-Ovum Fertilisation Process — NEET Biology
✅ Asked in NEET 2021Receptors for sperm binding in mammals are present on:
Receptors for sperm binding in mammals are present on:
Answer & NCERT explanation
Correct answer: D — Zona pellucida
Zona pellucida contains sperm binding receptors. It's the glycoprotein layer surrounding ovum where sperm recognition and binding occur during fertilization. Corona radiata is outer cell layer, perivitelline space is between zona pellucida and plasma membrane, vitelline membrane is not the primary binding site. NCERT describes zona pellucida's role in sperm-egg recognition.
Read more NCERT concept on the PYQ
The process of fusion of a sperm with an ovum is called fertilisation. During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms. Thus, it ensures that only one sperm can fertilise an ovum. The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma
NTA tests whether students understand that fertilisation begins when a sperm contacts the zona pellucida (outer glycoprotein layer) of the ovum, which triggers the block to polyspermy—preventing entry of additional sperms. This ensures monogamy of fertilisation. Students often confuse whether the block occurs before or after sperm entry, or mix up which structure triggers the block. Key trap: thinking multiple sperms can fertilise one ovum, or that the block happens at the plasma membrane first. Remember: zona pellucida contact → membrane changes → polyspermy block → only one sperm enters. This concept is fundamental to understanding early embryonic development and is tested to assess reproductive biology clarity.
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