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 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
 

Saturated fatty acids

Unsaturated fatty acids

no double bonds

one or more double bonds

abundant in fats

abundant in oils

more reduced

less reduced

more energy

less energy

high melting point

low melting point

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.

© Paul Billiet 2008