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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

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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
 

 
                          VEGETABLES
 
 

 

 
ANIMALS
 

 

   Aquatic animals   

Land animals e.g. cows, buffaloes and other milk producing animals.

 
        Animal wastes

 

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.

 HYDROCARBONS

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)

CH3 (CH2)16CH3

ii.           b – Carotene      

               (C40H56)

               The coloring hydrocarbons which impart yellow to red color in oil are known as carotenoids.

 

STEROL ESTERS

The sterol esters are esterified with fatty acids e.g.

 

 

WAXES

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.

 

 

ACYLGLYCEROLS

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.

 

TRIACYLGLYCEROLS;

 

 

DIACYLGLYCEROLS;

 

 

 

 

 

MONOACYLGLYCEROLS;

 

 

FATTY ALCOHOLS

The fatty alcohols are the long chain alcohols for example;

 

Cetyl alcohol

Stearyl alcohol

 

 

 

STEROLS

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:

 

Cyclopentanoperydrophenanthene

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:

 

CHOLESTEROL

 

FATTY ACID:

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

1.
2.
3.
4.
5.
6.
7..

  Lauric
Myristic
Palmitic
Stearic
Arachidic
Behenic
Lignoceric

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

C12: 0
C14: 0
C16: 0
C18: 0
C20: 0
C22: 0
C24: 0

 

            

 

 

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.

 

 

 

 

Table #

Source of energy

Carbohydrate

Protein

Lipid (fat and oil)

Amount of energy(kj/g)

       36

     16.5

          22.75

 

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.

1)      Digestion

2)      Absorption

DIGESTION:

                          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.

ABSORPTION:

                           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

 

 

 

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