Gametes And Fertilisation

Question 1

Gamete

Answer 1

specialized cell involved in sexual reproduction (e.g egg/sperm)

Question 2

Explain the process of fertilisation

Answer 2

1. Sperm arrives at egg
2. Chemicals from cells surrounding the egg trigger the acrosome reaction.
3. The acrosome (sperm lysosome) swells and fuses with the cell surface membrane of the sperm.
4. Digestive enzymes in the acrosome (sperm lysosome) are released by exocytosis.
5. These enzymes digest through the follicle cells, then zona pellucida.
6. The sperm fuses through the egg membrane.
7. Sperm haploid nucleus enters the egg, leaving the flagellum behind.
8. Cortical reaction; enzymes are released from cortical granules (egg lysosomes) by exocytosis causing the zona pellucida to harden to prevent any other sperm from entering.
9. Haploid nucleus of egg and haploid nucleus of sperm fuse together to produce a zygote (fertilised egg).

Question 3

Accrosome reaction

Answer 3

When digestive enzymes in the acrosome (sperm lysosome) are released by exocytosis to digest through follicle cells/zona pellucida.

Question 4

Cortical reaction

Answer 4

enzymes are released from cortical granules to harden the zona pellucida and prevent any other sperm entering the egg.

Question 5

Compare and contrast the cortical and acrosome reactions

Answer 5

• Both the cortical and acrosome reaction use lysosomes
• both release chemicals by exocytosis.
• The acrosome reaction involves the digestion of the zona pellucida, whereas the cortical reaction involves the thickening/hardening of the zona pellucida.