3.1.3 Lipids

lipids

2 groups = triglycerides + phospholipids

-formed by condensation reaction between glycerol + fatty acid which forms an ester bond where 3 molecules of water are removed

-fatty acid = RCOOH - the R group can be saturated (single bond) or unsaturated (double bond)

1) triglycerides + DIAGRAM

-1 molecule of glycerol + 3 molecules of fatty acid

-3 condensation reactions take place

-adaptations = high ratio of C-H bonds - source of energy, low ratio of mass:energy - good storage, non-polar + insoluble - no osmotic effect, high ratio of H:O - helps provide source of water when oxidised

2) phospholipids + DIAGRAM

-1 of the fatty acids of a triglyceride is substituted for a phosphate group

-adaptations = polar - can form a phospholipid bilayer for cell membrane, heads can join other molecules

test for LIPIDS

-emulsion test = mix food sample with ethanol + shake, then add water + shake and a white emulsion will form if present