Common unsaturated acids
C17H33COOH oleic acid ; C17H33COOH linoleic acid .
Difference between oils and fats Oils are liquids at ordinary temprature ( below 20 ° and contain lower fatty acids or unsaturated fatty acids .
Fats are solids or semisolids above 20 ° C and contain higher saturated fatty acids . Oils and fats act as “ energy reservoirs ” for the cells .
( ii ) Phospholipids Phosphate + glycerol + fatty acids + a nitrogen containing base .
Function of phospholipids are
1 . As emulsifying agents since they carry hydrophilic polar groups and hydrophobic non-polar groups .
2 . They absorb fatty acids from the intestine and transport to blood cells .
( iii ) Glycolipids They contain one or more simple sugars and are important components of cell membranes and chlorplast membranes .
( iv ) Steroids and Terpenes Menthol , camphor are common plant terpenes . Carotenoids and pigments are also terpenes .
( a ) Essential oils The volatile , sweet smelling liquids obtained from flowers , leaves , stems , etc . Example of terpenes are esters of lower fatty acid , e . g ., clove oil , rose oil , lemon oil .
( b ) Drying oils The oils which are converted into tough , transparent mass when exposed to air by oxidation polymerisation process are called drying oils . e . g ., Linseed oil , perilla , poppy seed oils .
Cotton seed oil and til oil are semidrying oils .