Lipids are the organic compound and natural product, comprises of mainly fatty acid and their derivatives. These are water insoluble but soluble in organic solvent. They are generally known as oil and fat. The major constituent of lipid are hydrocarbon, wax, ester sterol ester, tri terpene alcohol, free fatty acid,tri glycerol, fatty alcohol, di gylceride and mono glyceride .(1) These are widely distributed in food and are of great nutritional value. As compare to proteins and carbohydrates lipids produce more energy in animal metabolism(2). Fatty acids are the key component of oil, fat lipid and esterified waxes.
SOURCES OF OIL AND FAT
Oil and fats are procured from the terrestrial and aquatic sources which can be further divided in plant and animal kingdom. The animals in animal kingdom are cow, buffalo, goat and other milk producing animal. The oil bearing material among the vegetable kingdom consist of convention al and unconventional crops ie. rapeseed ,cotton seed ,soybean corn sunflower etc. fruits and nuts e.g, groundnut coconut , olive oil and palm oil fruit. The different sources of oil and fats can be shown as:
OILS AND FATS SOURCES
Land animals e.g. cows, buffaloes and other milk producing animals.
COMPONENTS OF OIL AND FATS AND LIPIDS:
The oil/fat or lipid contains fatty alcohol, esters, esterified wax sterol, wax esters, phospholipids hydrocarbon etc. the example of general lipid components are given below.
The colorless hydrocarbons may be saturated, unsaturated, straight chain, branched chain and cyclic. The conjugated hydrocarbons impart color to oils whereas non-conjugated are colorless. Examples of hydrocarbons are quoted here:
i. Octadecane (C18:0)
ii. b – Carotene
The coloring hydrocarbons which impart yellow to red color in oil are known as carotenoids.
The sterol esters are esterified with fatty acids e.g.
These waxes are also known as esterified waxes they have variety of industrial applications, they are the fatty acids esterified with long chain alcohols, e.g.
These are the esters of glycerin (polyhydric alcohols) with fatty acids. If the glycerine is esterified at three positions then the esters are triacylglycerols, if at two positions then the esters are diacylglycerols and if at only one position then the esters are monoacylglycerols.
The fatty alcohols are the long chain alcohols for example;
The sterols are a group of compounds of both plant and animal origin possessing a characteristic tetra-cyclic back bone. All sterols consist of 3 six membered rings and one five membered ring. These rings are joined and have a total of seventeen carbons, given as:
In most of the natural sterols, a methyl group is present at C10 and one is usuallypresent at C13. Many of the natural compounds having one alcoholic group in the ring structure are called sterols, for example cholesterol, ?-sitosterol etc. The cholesterol is common sterols in animal fats. The sterols procured from plant kingdom are known as phytosterols some of the examples are shown below:
The essential part of oil/fat or lipid is fatty acid. Fatty acid play important role for the characteristic of different oil and their sources. The fatty acids are further divided into long chain and short chain, saturated and unsaturated fatty acid.
SHORT CHAIN FATTY ACIDS
The chain length of short chain fatty acid starts from C1:0 to C10:0. The ratio of short chain fatty acid such as butyric caproic and caprylic (1.0 to 8.0%) are found in milk fat palm kernel and palmae seed oil. These short chain fatty acids can be produced by the oxidative degradation of monoenic, dienoic and trienoic long chain fatty acid fatty alcohol and hydrocarbon. The short chain carboxylic acids are also classified into mono carboxylic acid and di carboxylic acid.
SHORT CHAIN MONO CARBOXYLIC ACID
Fatty acid formulae no. of carbons
1-Methanoic acid H-COOH C1:0
2-Ethanoic acid CH3-COOH C2:0
3-Propanoic acid CH3-CH2-COOH C3:0
4-Butanoic acid CH3(CH2)2-COOH C4:0
5-pentanoic acid CH3(CH2)3-COOH C5:0
6-hexanoic acid CH3(CH2)4-COOH C6:0
7-heptanoic acid CH3(CH2)5-COOH C7:0
8-octanoic acid CH3(CH2)6-COOH C8:0
9-nonanoic acid CH3(CH2)7-COOH C9:0
10-decanoic acid CH3(CH2)8-COOH C10:0
SHORT CHAIN DICARBOXYLIC ACID
Acid formulae no. of carbons
1-oxalic acid HOOC-H-COOH C2:0
2-Malonic acid HOOCCH2COOH C3:0
3-Succinic acid HOOC(CH2)2COOH C4:0
4-Glutaric acid HOOC(CH2)3COOH C 5:0
5-adipic acid HOOC(CH2)4COOH C6:0
6-premilic acid HOOC(CH2)5COOH C7:0
7-suberic acid HOOC(CH2)6COOH C8:0
8-azelaic acid HOOC(CH2)7COOH C9:0
9-sebacic acid HOOC(CH2)8COOH C10:0
LONG CHAIN FATTY ACID
The number of carbon in long chain fatty acid starts from C10:0. The neutral and polar lipids after sponification produce long chain fatty acid as main product. These are also divided into saturated and unsaturated fatty acids.
COMMON LONG CHAIN SATURATED FATTY ACID
CH3 (CH2)10 COOH
CH3 (CH2)12 COOH
CH3 (CH2)14 COOH
CH3 (CH2)16 COOH
CH3 (CH2)18 COOH
CH3 (CH2)20 COOH
CH3 (CH2)22 COOH
COMMON LONG CHAIN UNSATURATED FATTY ACID
Unsaturated fatty acids with structural formulae:
Lipids as source of energy
Human use carbohydrates, protein and fat as source of energy. In case of animal metabolism 1g of fat provides more energy in term of calories than carbohydrates and protein. One gram of fat provides 9 cal while carbohydrate and protein provides 4cal and 6.6cal respectively. So consumption of oil and fat provide your body more energy than other sources.
Source of energy
Lipid (fat and oil)
Amount of energy(kj/g)
HUMAN AND LIPID METABOLISM
Lipids act as fuel for human body. As we know they are big source of energy for human. Lipid metabolism is a process of breakdown of triglyceride into monoglyceride and then into fatty acid. There are two steps of lipid metabolism.
Is a splitting process of lipid into simple unit of fatty acid. This process is starts from mouth cavity and ends in small intestine of human body. The chemical digestion starts from mouth cavity in the presence of lingual lipase. Then material transported into stomach for further chemical and mechanical digestion. Gastric lipase (chemical) and peristalsis (mechanical) in stomach play important role in digestion of lipid. The major digestion and absorption occurs in small intestine. The chemicals, pancreatic lipase and bail salt-dependent lipase transport from pancreas for breaking of lipid molecules. The complete breakdown of triglyceride into simple fatty acid and glycerol is done in small intestine after series of chemical and mechanical digestion.
The absorption is second step of lipid metabolism in human body. First fatty acids are absorbed in inner lining of small intestine of digestive track. And then further breakings of fatty acids are occurred in order to produce fuel for body. The metabolic activity starts from addition of Co-A with fatty Acid in the presence of ATP hydrolysis. After that acyl-CoA is formed in cytoplasm epithelial cell, as result of Beta oxidation acyl group synthesis acetyl group and acyl group ( carbon less)
Following are the major steps of fatty acid breakdown in human body.
Importance of saturated and unsaturated fatty acid