The Open Door Web Site : IB Biology : Biochemistry : Lipids

MOLECULES OF LIFE

Lipids (elements C, H, O)

More hydrogen than carbohydrates (more reduced). Insoluble in water, soluble in organic solvents (alcohols, acetone, chloroform etc)

Fatty acids: carboxylic acid + long hydrocarbon chain

Satyrated fatty acids

Fats and Oils: fatty acids + glycerol (1, 2 or 3 = mono , di or triglycerides)


Two fatty acids joining glycerol

Phospholipids: in lipoprotein membranes (plasma, nuclear, mitochondrial etc.)

Steroids: multiple ring structures (e.g. cholesterol)

Functions: cell membrane structure, digestion (help to emulsify fats), hormones (testosterone etc), vitamins (e.g. Vitamin D), poisons.

Waxes: long chain alcohol + fatty acids

Water proof coating to leaves, fur feathers, insect exoskeletons. Used by bees to construct their honey combs.

FUNCTIONS OF LIPIDS IN GENERAL

STRUCTURAL	biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys)
ELECTRICAL INSULATION	myelin sheath round axons
THERMAL INSULATION	subcutaneous fat deposits.
WATER PROOFING	waxes and oils
ENERGY STORE AND SUBSTRATE	very condensed form of energy (37 kJ g-1) used by animals and seeds.
HORMONES	steroids
VITAMINS	precursor to Vitamin D
BUOYANCY	oil droplets in plankton.