Question

Sperm receptors are inactivated by

• A. acrosin
• B. hyaluronidase
• C. fertilisin
• D. cortical enzymes

Answer 1

The correct option is D cortical enzymes

The sperm receptors are present on the oocyte and can be inactivated by the cortical granule enzymes. The cortical granules enzymes are present in secretory vesicles just beneath the oolemma. When these secretory vesicles are exocytosed outside the oolemma, they interact with the zona pellucida layer and harden it.

The anterior most region of the sperm has acrosome. The acrosome houses hydrolytic enzymes that help the sperm to penetrate through different layers of the secondary oocyte. The hydrolytic enzymes include acrosin (helps penetrate through the zona pellucida) and hyaluronidase (helps dissolve the hyaluronic acid in the corona radiata).

The surface of the oocyte is coated with a chemical substance called fertilisin. Fertilisin plays an important role in the recognition of gametes of the same species. It interacts with antifertilisin found on the surface of the sperms and initiates fertilisation.