Question

The glycoprotein, fertilizin is secreted by
A. Ovum
B. Ovary
C. Sperm
D. Testis

Answer 1

The fertilizin is a glycoprotein that binds the sperm to the egg’s surface. A glycoprotein is made up of monosaccharides and amino acids. The main purpose of fertilizin is to react with the antifertilizin.

Complete answer:
An acidic protein named antifertilizin is secreted from the plasma membrane of the sperm which helps in checking the compatibility between the egg and the sperm. Basically, its work is to check if the sperm fertilizing the egg is of the same species or not.
Fertilizin is secreted by the ovum. When sperm meets the ovum in the fallopian tube, the ovum releases fertilizin. The fertilizin-antifertilizin reaction is species-specific, thus if the sperm is from any other species, the ovum will not get fertilized from it. If the species of the ovum and sperm are the same, fertilizin-antifertilizin interaction paves the way for the sperm to fertilize the ovum. Due to the presence of fertilizin on the surface of the egg cytoplasm, sperm gets adhered to it.

Hence, the correct answer is option (A).

Additional information:
After the sperm gets attached to the ovum due to fertilizin-antifertilizin interaction, the sperm needs to fertilize the egg. For this purpose, the acrosome of the sperm secretes a chemical substance called lysine which helps in the penetration of the egg. Once a sperm enters the ovum, the membrane of the ovum blocks the entry of other sperms.

Note: The major functions of the fertilizin are to make the surface of the ovum sticky to let the sperm attach to it, help sperm to penetrate the egg, initiate fertilization, and to prevent polyspermy of the egg.