LIPIDS
Lipids are heterogeneous group of compounds with same properties Fat is the common household name gives to lipids carbohydrates fats are organic compounds composed of carbon hydrogen and oxygen but they differ from carbohydrates in that they contain much less oxygen and much greater proportions of carbon and hydrogen seventy six percent carbon twelve percent oxygen and twelve percent hydrogen are present in fats true fat has one molecule of organic ester of glycerol and three molecules of fatty acids fats vary in their structure due to the presence of different fatty acids with glycerol molecules if the glycerol in a fatty acid is combined with three fatty acid units such fats are called triglycerides fats are insoluble in water and soluble in organic solvents like ether benzene or chloroform their cooking properties depend upon the type of fatty acids present in them
Classification:::
Lipids are classified into ::
(a) simple lipids
(b) compound lipids
(c) waxes
(d) derived lipids
Simple Lipids::
These are esters of fatty acids with various alcohols fats are esters of fatty acids with glycerol oils are liquid at 20.c while fats are solid at 20.c Combination of fatty acids and sterol alcohol form cholesterol Food fats contain neutral fats fat is stored in the body as adipose tissue This is also neutral fat
Compound Lipids::
when fatty acids and glycerol combine with other organic compounds they are known as compound lipids Examples of compound lipids are phospholipids and glycolipids
Waxes::
These are esters of higher fatty acids and alcohol other than glycerol Cholesterol esters sterol esters esters of fat soluble vitamins are the common waxes
Derived Lipids::
Substances derived from fat on hydrolysis or by enzyme activities are called derived fats examples of derived lipids are fatty acids like stearic acid linoleic acid butyric acid alcohols like glycerol cetanol and lanol Sterol alcohols like cholesterol ergosterol and sistosterol are also derived fats
Sterols are nutritionally important they are classified as animal sterols plant sterols and mycosterols
Cholesterol is the precursor of steroid hormones and bile salts Hormones like progesterone oestrogen and adrenal corticoids contain cholesterol Sodium glycocholate and sodium taurocholate and the bile salts have cholesterol in them cholesterol esters produced by the liver regulate the cholesterol content in the blood it is present in all animal and human tissues the white matter of the brain has 1-14 percent cholesterol while the grey matter has 60 percent on dry basic sebum secreted by sebaceous gland also has large amounts of cholesterol
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