Question

Animal Physiology Question

1. Sperm rely on both microtubules and microfilaments for key biological processes. Explain the role of microtubules and dynein in movement of sperm. Explain the role of actin in the process of fertilization.

Answer 1

1.The movement of the sperm is carried out with the help of the flagella (the tail).The tail is made up of

1. a central skeleton constructed of 11 microtubules called as axoneme
2. A cell membrane that covers the axoneme
3. Spirally arranged mitochondria arranged around The membrane.

The movement of the flagella is carried by the sliding movements of the axonemal doublet microtubules by the molecular motor dyenin.Dyenin molecule drives the sliding movement of the microtubules which causes the motvement of the flagella of the sperm.

ROLE OF ACTIN IN FERTILISATION

In order for fertilization to occur, the spermatozoa must undergo a series of biochemical modifications called capacitation. Only a sperm which has undergone capacitation can undergo the acrosome reaction which enables sperm to penetrate into the egg and fertilize it after binding with the sona pelucida. During the capacitation process,the Polymerization of globular actin to filamentous actin occurs during capacitation.
F-actin formation is important for the translocation of phospholipase C from the cytosol to the sperm plasma membrane during capacitation. For the occurance of acrosome reaction,the F-actin undergo depolymerization, which enables the outer acrosomal membrane and the overlying plasma membrane to come in closercontact and fuse. The binding of the capacitated sperm to the zona pellucida induces a fast increase in sperm intracellular calcium leading into the activation of actin severing proteins that breaks down the actin fibers allowing the acrosome reaction to take place.