Which part of the sperm help in its entry into the cytoplasm of the ovum ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Acrosome
Option (1) Plasma membrane — Incorrect. The plasma membrane covers the whole sperm; it does not help it enter the ovum.
Option (2) Nucleus — Incorrect. The nucleus carries the haploid chromosomes into the ovum; it does not make the way in.
Option (3) Neck — Incorrect. The neck joins the head to the middle piece.
Option (4) Acrosome — Correct. The acrosome is the cap on the head, filled with enzymes. Its secretions help the sperm pass the zona pellucida and the plasma membrane into the cytoplasm of the ovum.
NCERT Extract:
Fertilisation and Implantation – “… During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum (Figure 2.10) 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 membrane. This induces the completion of the meiotic division of the secondary oocyte.”