Question

The release of the contents of cortical granules, ________.

A. Occurs after a single sperm cell enters the egg.

B. In some animal species, causes the jelly layer of the egg to physically change and lift away.

C. Is the cause of a second reaction in which calcium ions sweep across the egg cell from the point of cell entry.

D. Both A and B describe the release of the contents of cortical granules . E. All of the above describe the release of the contents of cortical granules.

Answer 1

Answer

In the oocytes there are membrane-bound secretory organelles called cortical granules. The contents of these granules are released after fertilization, from the oocyte. This release of cortical granule contents is known as cortical reaction. This prevents the polyspermy, that is the fusion of egg with multiple sperms. This prevention is facilitated by the oocytes plasma membrane, as it is depolarized by opening of Na⁺ channels. This makes Na⁺ ions move into the egg along with water absorption. This makes the vitelline layer below the plasma membrane swell and lift from the plasma membrane.

During fertilization, the calcium ions are released from egg cell in response to the interaction of the sperm and the egg plasma membrane. As calcium ions releases, sperm receptors are lysed, and the vitelline layer of the egg is hardened preventing polyspermy.

From the above explanation, the release of cortical granule contents occurs after sperm enters the egg, causes the jelly layer to change physically, causes release of calcium ions release from the egg.

Therefore, option E is correct.