3.11, 3.12

Question 1

What is the acrosome in sperm and its function?

Answer 1

Is a specialised lysosome which is storage site for enzymes that digest the layers surrounding the ovum and allows male nucleus to penetrate.

Question 2

How is the nucleus adapted in the sperm head?

Answer 2

The highly condensed haploid chromosomes reduce the amount of energy needed to transport it.

Question 3

Why are the mitochondria in a sperm cell found in the middle section?

Answer 3

So that the ATP can be quicly provided to the lashing tail.

Question 4

What is the function of the microtubules found in the sperms tail?

Answer 4

They produce the whip-like movements, help it swim to the ovum.

Question 5

Function of sperm tail/flagellum

Answer 5

helps it swim/propel itself in a liquid environment.

Question 6

What is the function of the zona pellucida?

Answer 6

It is a clear protective, jelly-like layer that surrounds the oocyte.

Question 7

What is external fertilisation?

Answer 7

It is fertilisation that occurs outside the body where the gametes are released into the environment where they meet and fuse. Usually seen in aquatic species, like fish.

Question 8

What is internal fertilisation?

Answer 8

This involves the transfer of male gametes directly to the female. This does not guarantee fertilisation but makes it much more likely.

Question 9

What is fertilisation?

Answer 9

The meeting and fusion of male and female gamete nuclei.

Question 10

How does fertilisation happen in mammals?

Answer 10

1. Sperm surround the egg cell.
2. When the sperm heads touch the surface of the egg, the acrosome reaction is triggered.
3. Digestive enzymes are released from the acrosome which digest the cells and zona pellucida. It takes multiple sperm to penetrate through protective layer.
4. One sperm will break through and reach the oocyte cell membrane.
5. The cortical reaction occurs.
6. Forms fertilisation membrane which repels other sperm.
7. Second meiotic division happens and two haploids fuse to form diploid. Membranes fuse and zygote is formed.

Question 11

What is the acrosome reaction?

Answer 11

When digestive enzymes are released from the opened acrosome and begin to digest the zona pellucida.

Question 12

What is the cortical reaction?

Answer 12

Cortical granules are released by exocytosis from the cytoplasm of the ovum, released into the zona pellucida. This destroys sperm-binding sites and thickens the jelly. This prevents other sperm from entering.