Gametes And Fertilisation 2

Question 1

Where does fertilisation occur and how does the egg get there

Answer 1

Fertilisation occurs in Fallopian tubes. Cilia move egg to uterus

Question 2

Process of fertilisation

Answer 2

1) Sperm reach ovum
2) Chemicals are released from cells surrounding ovum, triggering acrosome reaction.
3) Acrosome reaction occurs
7) Sperm cell membrane fuses with ovum cell membrane
8) Only sperm nucleus enters ovum
9) cortical reaction occurs
10) Nuclei of sperm and egg fuse, causing diploid number to be restored

Question 3

Cortical reaction

Answer 3

Cortical reaction is when cortical granules release contents to thicken the zona pelucida, so sperm cells can’t reach egg cell membrane

Question 4

Acrosome reaction

Answer 4

Acrosome reaction is when chemicals from ovum cause Acrosome to fuse with the sperm cell membrane and acrosin is released(exocytosis). Acrosin digests zona pelucida so sperm cell membrane can fuse with egg cell membrane

Question 5

Zygote

Answer 5

Zygote is a cell formed from 2 gametes after fertilisation, it has the diploid number of chromosomes.

Question 6

Describe structure of egg

Answer 6

Egg has follicle cells, then have the zona pelucida, then there’s the cell membrane. Then, in the cytoplasm there are lysosomes, lipid droplets and a haploid nucleus

Question 7

Adaptations of the egg

Answer 7

Adaptations of egg include:
lipid droplets which supply energy for cell division.
Haploid nucleus to restore diploid number
Has Lysosome, thickening of zona pelucida

Question 8

Compare acrosome and lysosomes

Answer 8

Both contain hydrolysis enzymes
Both are surrounded by membrane.
Acrosome only found in sperm, lysosomes not found in sperm.
Only 1 acrosome found in sperm whereas in some cells there are many lysosomes.
Acrosome digests zona pelucida whereas lysosomes digest cells