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.