Question

The function of cortical granules of an oocyte is to help in

• A. The formation of vitelline membrane
• B. Completing its maturation division
• C. The synthesis of fertilization membrane
• D. The synthesis of yolk

Answer 1

Answer: (C)

The synthesis of fertilization membrane

The increased level of intracellular calcium produces thousands of cortical granules in the egg cortex (region close to the plasma membrane). It releases enzymes, various proteins, and other substances by exocytosis into the space between the plasma membrane and the vitelline envelope. Some of the enzymes dissolve the protein linking the two membranes thus, space enlarges as additional substances released by the cortical granules raise the osmotic pressure, which causes an influx of water from the surroundings. Thus, the vitelline envelope becomes elevated away from the plasma membrane and forms the fertilization envelope, a hardened covering that prevents entry of additional sperm. Therefore, the correct answer is option C.