Chemistry P2

• Menstrual cycle:

  • FSH-->OESTROGEN-->LH-->PROGESTERONE
• FSH:

  • produced by pituitary gland
  • matures egg
  • stimulates oestrogen
• Oestrogen:

  • produced by ovaries
  • thickens uterus lining
  • stimulates LH
  • inhibits FSH
• LH:

  • produced by pituitary gland
  • releases egg
  • stimulates progesterone
• Progesterone:

  • produced by ovaries
  • maintains thick lining of uterus
  • inhibits FSH & LH
• Menstrual cycle:

  1. day 1--> menstruation starts, uterus lining breaks down
  2. day 4-14--> uterus lining builds up again
  3. day 14--> ovulation
  4. day 14-28--> uterus wall maintain, if no fertilised egg lands then uterus lining breaks down
• Oral contraceptives:

  • contains hormones that inhibit FSH (no eggs mature)
• Injection/implant/skin patch:

  • slow release of progesterone, inhibits FSH + LH
• Barrier methods: condoms/diaphragms

  • stops sperm reaching egg
• Intrauterine devices:

  • prevents implantation of an embryo or hormone release
• Spermicide:

  • kills or disables sperm (70%-80% effective)
• Sterilisation:

  • cutting or tying fallopian tubes/sperm ducts
• Fertility drug contains FSH + LH which stimulates ovulation
• PROS of fertility drug:

  • helps women get pregnant
• CONS of fertility drug:

  • doesn't always work
  • unexpected multiple pregancies
• IVF treatment:

  1. giving mother FSH + LH to stimulate maturation of several eggs
  2. eggs then collected from ovary
  3. eggs mixed with sperm --> fertilisation
  4. fertilised egg divides
  5. embryo forms
  6. embryos then inserted into mother's womb
• PROS of IVF:

  • gives infertile couple a child
• CONS of IVF:

  • expensive
  • risk of multiple pregnancies
  • low success rates--> 26%
  • emotionally & physically stressful
• Microscopy techniques:

  • helped to improve techniques of IVF (therefore success rate)
  • specialised micro-tools developed to use on eggs + sperm under microscope
  • used to remove single cells from embryo for genetic testing--> growth of embryo can be continuously monitored to identify successful pregnancy
• Adrenaline:

  • prepares you for 'fight or flight'
  • produced by adrenal gland
  • increases heart rate and boosts delivery of oxygen + glucose to the brain & muscles
• Thyroxine:

  • released by thyroid gland in response to TSH
  • stimulates basal metabolic rate
  • plays important role in growth + development
• Negative feedback loop: thyroxine

  • when levels increase, detected by receptors in the brain
  • this inhibits release of TSH
  • this inhibits release of thyroxine
  • levels fall
• Plants produce hormones to coordinate & control growth and respond to light (phototropism), gravity (geotropism) and water ( hydrotropism)
• unequal distribution of auxins cause unequal growth rates in plant roots & shoots
• Auxins:

  • control growth at the end of the shoots & roots
  • once they're produced in the tips, they dissolve and diffuse backwards along the shoots/roots
• Auxins in shoots --> stimulate growth
• Auxins in roots --> inhibit growth
• Auxins always accumulate on the shaded side and the lower side
• Auxins in shoots:

  • positively phototropic --> grow towards the light
  • plant receive more light = faster photosynthesis

  
  

  • negatively geotropic --> grow away from ground