Lipids and its Types

Lipids and its types

Definition of Lipids

The lipids are a group of heterogenous water insoluble non-polar organic compounds of the plant and animal origins which are soluble in Bloor’s reagent (a mixture of diethyl ether and ethyl alcohol in the ratio of 2:1) e.g. Oils, fats, waxes, butter, fat-soluble vitamins (A, D, E, K) etc.

Bio-medical Importance of Proteins

1.	Energy Supply
2.	Insulation of vital organs
3.	Regulation of optimum body temperature

Types of Lipids on the basis of structures by Bloor

1.	Simple Lipids or Glycerides
	a)    Fats and Oils b)    Waxes	(Triglycerides)             (Monoglyceride) [C15H31-COO-C30H61]
2.	CompoundsLipids/Conjugated Lipids
	a)    Phospholipids or Phosphoglycerides b)    Glycolipids           c)    Lipoproteins	(Phosphate derivatives of lipids) (Carbohydrate derivatives of lipids) (Protein derivatives of lipids)
3.	Steroids	(non-saponifiable fats)
	a)    Cholesterol [C27H45OH] b)    Cholic acid [C24H40O5] c)    Progesterone [C21H30O2] d)    Vitamin D

           

A) Fats and Oils (Triglycerides or triacylglycerols)

Fats and oils are simple lipids that are triesters of fatty acids (long chain carboxylic acids containing even number of carbon atoms) with polyhydric alcohol, glycerol. Hence they are also called Triglycerides or Triacylglycerol.

Difference b/w Fats and Oils

Fats

1.   Fats are solid state esters (triglycerides) of fatty acid and glycerol at room temperature.         

2.   Fats usually come from animal sources.

3.   Fats contain a higher proportion of saturated fatty acids in their esters.

4.   Fats have low iodine number (less unsaturation).

5.   Usually fats are simple glycerides in which all the three –OH groups of glycerol are esterified with same acid.

Oils

1.         Oils are liquids state esters (Triglycerides) of fatty acids and glycerol at room temperature.

2.         Oils come from vegetable sources.

3.         Oils contain a higher proportion of unsaturated fatty acids in the in their esters.

4.         Oils have high iodine number (except coconut and fish oils.).

5.         Usually oils are mixed glycerides containing two or more different fatty acid parts.

B) Waxes

Waxes are naturally occurring esters of long–chain monohydric alcohols and long-chain fatty acids (C16 or greater). Thus on hydrolysis wax gives monohydric alcohol [while fat gives trihydric alcohol, glycerol]. They are water-insoluble, flexible, non-reactive, low melting solids with a waxy feeling. e.g. Bee’s wax is an ester of palmitic acid and mericyl alcohol (C₃₀H₆₁OH) and its chemical name will be mericyl palmitate. CH₃.(CH₂)₁₄.COO.(CH₂)₂₉.CH₃ OR C₁₅H₃₁COOC₁₆H₃₃, spermacetic wax C₁₅H₃₁COO-C₁₆H₃₃ (Spermaceti consists principally of cetyl palmitate (the ester of cetyl alcohol, C₁₆H₃₃OH and palmitic acid), C₁₅H₃₁COO-C₁₆H₃₃).

Cetyl alcohol, also known as 1-hexadecanol and palmityl alcohol, is a fatty alcohol with the formula CH₃(CH₂)₁₅OH. At room temperature, cetyl alcohol takes the form of a waxy white solid or flakes. The name cetyl derives from the whale oil (Latin: cetus) from which it was first isolated.

Simple and Mixed Glycerides

When the three OH group of glycerol are esterified with the same acid, the triglyceride is known as Simple Glyceride (Simple Fat).

If two or more OH groups of glycerol are esterified with different fatty acids, then the triglyceride is known as Mixed Glyceride or Mixed triglycerides or Mixed triacylglycerols (Mixed Fats). Cooking oils and fats are mixed triglycerides containing all the three different fatty acids.