Fertilisation

Question 1

How does a spermatozoa penetrate the first, corona radiata layer of the oocyte?

Answer 1

Membrane-bound enzymes in the surface membrane which surrounds the head of the spermatozoa

Question 2

What surface protein on the spermatozoa binds with the ZP3 glycoprotein receptor on the bona pellucida of the oocyte?

Answer 2

Fertillin

Question 3

What reaction is triggered by the binding of spermatozoa to the ZP3 receptor on the bona pellucida of the oocyte?

Answer 3

Acrosomal reaction

Question 4

Fusion of the head of the first spermatozoa to reach the plasma membrane with the secondary oocyte activates mechanisms which prevent polyspermy. What are these mechanisms?

Answer 4

Depolarisation of oocyte membrane prevents other spermatozoa from fusing
Wave of intracellular calcium release causes release of cortical granules by the secondary oocyte which inactivate ZP3 and make the bona pellucida impermeable

Question 5

Calcium depolarisation of the membrane of the secondary oocyte prevents polyspermy but also has a second effect. What is this?

Answer 5

Allows the secondary oocyte to complete meiosis II

Question 6

What is involved in capacitation of sperm?

Answer 6

Flagella beat more quickly under the influence of seminal fluid
Vaginal secretions promote removal of glycoproteins from the heads of the spermatozoa