Biology · Human Reproduction · NEET
The acrosome stores enzymes. When the sperm reaches the ovum, these enzymes are released and dissolve the outer coverings of the egg — first the corona radiata, then the zona pellucida. This makes a path so the sperm head can reach and fuse with the plasma membrane of the ovum. Without a working acrosome, the sperm cannot enter the egg, so fertilisation fails. NEET tests this as: acrosome = enzymes that help fertilisation.
The acrosome is in the HEAD, not the middle piece. It is a cap-like structure covering the anterior (front) part of the sperm head, which contains the haploid nucleus. Students often confuse it with the middle piece, but the middle piece has mitochondria that make energy for the tail. NEET 2025 asked exactly this: Head = genetic material, Middle piece = energy, Acrosome = enzymes, Tail = motility.
NCERT only says the acrosome is 'filled with enzymes that help fertilisation' and does not name a specific enzyme for the Class 12 Human Reproduction chapter. So for NEET, the safe answer is 'hydrolytic/digestive enzymes that help the sperm penetrate the ovum'. Do not write a specific enzyme name in a fill-in answer unless the option gives one, because NCERT keeps it general.
The acrosomal enzymes help the sperm cross the corona radiata (the outer layer of follicle cells) and then the zona pellucida (a thick transparent layer with sperm-binding receptors). After crossing these, the sperm reaches the plasma membrane of the ovum. Remember the order from outside to inside: corona radiata → zona pellucida → plasma membrane.
No. The acrosome does NOT move the sperm. Movement (motility) comes from the tail, and the energy for that movement comes from the mitochondria in the middle piece. The acrosome only carries enzymes for penetrating the egg. Mixing these up is a common NEET trap.
Match List-I and List-II. List-I (A. Head; B. Middle piece; C. Acrosome; D. Tail) List-II (I. Enzymes; II. Sperm motility; III. Energy; IV. Genetic material) Choose the correct answer from the options given below:
Receptors for sperm binding in mammals are present on
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A cap-like structure on the front of the sperm head, filled with enzymes that help the sperm penetrate the ovum during fertilisation.
On the anterior (front) part of the sperm head, covering the haploid nucleus like a cap.
Acrosome = enzymes to penetrate the egg (in the head). Middle piece = mitochondria that make energy for the tail's movement.
No. The Class 12 Human Reproduction chapter just says the acrosome is filled with 'enzymes that help fertilisation', without naming one, so keep your answer general.
If the acrosome or its enzymes do not work, the sperm cannot dissolve the ovum's outer layers or enter the egg, so fertilisation cannot occur.
