Revision:Aqa biology synoptic paper - lipids

Triglyceride is 3 fatty acids attached to a glycerol molecule. Saturated (fats) /unsaturated (. Phospholipid is 2 fatty acids, one glycerol and one phosphate group (uneven charge distribution).


  • Thermal insulation as adipose tissue. Enables internal conditions to help stay optimum for enzyme-controlled reactions.
  • Phospholipid bilayer forms a barrier to water and water-soluble substances.
  • Oestrogen produced by developing follicle cells. Stimulates the growth of endometrium, inhibits further secretions of FSH and stimulates the pituitary gland to release LH. So it enables menstrual cycle to occur. Enables endometrium to be maintained throughout pregnancy (secreted by placenta). Stimulates growth of breast tissue to prepare for lactation. Causes growth of cartilage in pelvic girdle of girls during puberty.
  • Low oestrogen levels give a greater risk of osteoporosis.
  • Products of triglyceride digestion can be transported into epithelial cells via bile salts (a steroid) forming micelles.
  • Testosterone growth of male secondary sexual characteristics e.g. pectoral girdle & thorax grow. Sperm production.
  • Cholesterol increases stiffness of plasma membranes. Used to make the neurotransmitter acetylcholine. *Used to make bile salts in liver. Some is deposited on the skin to make it more waterproof.