Question

How does the sperm break through the egg membrane? Choose the option you think is right.
A. Tears a hole in the membrane
B. Dissolves the membrane with chemicals
C. Bites through the membrane with teeth
D. Squeezes through the gaps in the membrane

Answer 1

Fertilization is the fusion of a paternal sperm nucleus with a maternal egg nucleus to generate the main nucleus of an embryo. The essence of fertilisation in all organisms is the union of the genetic material of two separate sex cells, or gametes, each of which contains half of the species' chromosomes. This occurs in the female reproductive tract in case of internal fertilization where the sperm breaks into the egg membrane.

Complete solution:
Option A: Sperm penetrates the egg through enzymatic reactions thus it does not tear a hole in the egg membrane.
Thus, option A is not correct.
Option B: This option is the nearest to the answer as the sperm penetrates the egg through enzymatic reactions of which the acrosomal reaction is of prominence. In an acrosomal reaction the acrosome of the sperm releases certain chemicals which dissolves the egg membrane allowing for the sperm nucleus to enter the egg membrane.
Thus, option B is the correct answer.
Option C: Sperm do not have any teeth like structure. Thus, this option is incorrect.
Option D: The cells of the egg membrane are cemented by hyaluronic acid – a polysaccharide and their egg membrane do not have any gaps through which sperms could squeeze.
Thus, option D is not correct.

Therefore, Option B. dissolves the membrane with chemicals is the correct answer

Note:
Egg cell is bound by a double membrane formed by zona pellucida and corona radiata. The oocyte comes into contact with the surviving capacitated sperm, which are drawn to it by chemical attractants generated by the corona radiata cells. The sperm must pass through two layers of protection before reaching the egg. The sperm initially tunnel through the corona radiata cells. The sperm then attach to receptors in the zona pellucida when they come into touch with it. This triggers the acrosomal reaction, in which the sperm's enzyme-filled "cap," or acrosome, releases its digesting enzymes that have been stored. These enzymes clear a passage for sperm to reach the egg via the zona pellucida. Finally, a single sperm contacts sperm-binding receptors on the plasma membrane of the oocyte.