Fertilisation

• What are some features of a sperm?

  Tail

  Mitochondrion- provides energy

  Haploid nucleus

  Acrosome

  Head
• What is the function of the tail of a sperm?

  It is made from motor proteins which use ATP to propel the sperm forwards
• What is the function of the acrosome?

  It swells and bursts when the sperm embeds in the zona pellucida and the enzymes in the acrosome digest the follicle cells and the zona pellucida, allowing the cell membranes to fuse
• What happens when sperm reach the ovum during fertilisation?

  1. Sperm reach the ovum
  2. Chemicals are released from surrounding cells, leading to the acrosome reaction
  3. Acrosome swells, fusing with the cell surface membrane
  4. Digestive enzymes in the acrosome are released
  5. Enzymes digest through the follicle cells and the zona pellucida
• What happens after the sperm enters the zona pellucida?

  1. Sperm fuses with the ovum membrane
  2. Sperm nucleus enters the ovum
  3. Enzymes released from lysosomes in the ovum thicken the zona pellucida, preventing entry of other sperm
  4. Nuclei of the egg and sperm fuse
• What happens during the hardening of the zona pellucida?

  After the acrosome reaction, the egg and sperm cell fuse. Following this, the lysosomes undergo a condensation reaction (cortical reaction)
• Why are lysosomes important in a cell?

  They are needed for a cortical reaction during which the zona pellucida hardens to prevent excess sperm from reaching the egg
• What are the features of an egg cell (ovum)?

  Surrounded by follicle cells from the ovary, have a haploid nucleus, lipid droplets (energy sources), lysosomes, zona pellucida