fertilisation 1

• gametes

  • sex cells of an organism eg sperm or eg
  • have only one copy of each chromosome- 23 single chromosomes
  • form via meosis
• sperm cells

  • many mitochondria- provide energy from respiration so flagellum can move
  • enzymes in acrosome- digest through zona pellucida and cell membrane of egg
  • flagellum- enables swimming/ movement to the egg
• egg cells

  • much larger, internal space for food to nourish embryo
  • follicle cells form protective coating
  • jelly-like glycoprotein layer- zona pellucida- forms impermeable barrier after ferilisation preventing polyspermy
• fertilisation

  • the fusion of the nuclei of a male gamete and a female gamete
• 1. acrosome releases enzymes that digest a path through the zona pellucida(acrosome reaction)
  2. egg cell immediately releases contents of vesicles(cortical granules) into space between ZP and cell membrane-cortical reaction
  3. chemicals in cortisol granules cause ZP to thicken and harden, preventing polyspermy, only one sperm can fertilise the egg
  4. nucleus of sperm enters egg and fuses with nucleus=zygote(46 chromosomes)
  5. zygote undergoes mitosis and forms an embryo- many new cells become specialised
• capacitation

  • cell surface membrane of sperm head stripped of glycoproteins- capable of fertilisation
  • acrosome reaction- acrosome swelling and fusing with cell membrane, releasing digestive enzymes(via exocytosis) which digest/hydrolise glycoproteins