In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are ________.
A) the acrosomal reaction and the formation of egg white
B) the cortical reaction and the formation of yolk protein
C) the jelly coat of the egg and the vitelline membrane
D) membrane depolarization and the cortical reaction

Question

Quizplus · Accepted Answer

The "fast block" is caused by a membrane depolarization, which is a quick response to the penetration of the sperm. This depolarization makes the egg temporarily unresponsive to additional sperm. The "slow block" is caused by the cortical reaction, in which cortical granules release their contents to form a fertilization envelope around the egg. This process takes longer than the membrane depolarization, but it is more permanent and prevents the entry of additional sperm.

In Sea Urchins, the "Fast Block" and the Longer Lasting