Question

What is capacitation with reference to mammalian sperm?

Answer 1

Sperm capacitation is the physiological change and the sperms get the ability to penetrate into the female reproductive tract and fertilize a mammalian egg. In simple words the process of getting the ability to fertilize the egg in females is called a capacitation. Main terms involved in capacitation are fertilization, motility patterns, acrosome reaction, bio chemical modification and physiological modification. During mammalian capacitation the sperm which is capacitated penetrates into the ovum and make contact with zona pellucida

Complete answer:
Sperm goes into the female reproductive tract to fertilize the secondary oocyte. This process or mechanism is called a biochemical event. During this process sperm movement is normal and makes itself mature enough to undergo capacitation. So the sperm gains the ability to fertilize ovum and contact the fluids in the female genital tract. Sperm motility patterns correlates with the capacitation. This process is known as hyperactivation. Sperm changes their head and tail pattern while undergoing capacitation. This changing in sperm is called an acrosome reaction and motility changes. After the sperm joins with the egg in the uterus the sperms undergo an exocytotic process which is also named as an acrosome reaction. Two modifications occur while sperm undergoes capacitation. There are multiple physiological and biochemical modifications. Bio chemical modification increases the membrane fluidity and permeability to bicarbonate and calcium ions. Sperm moves either fast or slow. Fast movement of sperm happens only at the time of sperm leave from epididymis. Slow movement involves pattern movement of sperm. The last stage of capacitation is known as protein tyrosine phosphorylation. So in this stage sperm gets capacity to fertilize and get the ability to carry acrosome reaction which is induced by the progesterone. So the hyper activation of sperm is induced. After that sperm fertilize the oocyte.

Note:
For the capacitation process some of the molecules are essential. They are $HC{O^ - }_3$, serum albumin, $C{a^{2 + }}$. Capacitation also involves loss of cholesterol of the human body, activates phospholipases, and changes the stability of sperm membrane. Some of the ions, molecules and reactive oxygen species affect capacitation also. They are cholesterol efflux, intracellular $C{a^{2 + }}$ and its channels and also pH plays an important role in capacitation.