• Fatty acids are carboxylic acids with hydrocarbon chain ranging from 4 to 36 caarbon atom ie. C4 to C36. In some fatty acids, this hydrocarbon chain is unbranched and fully saturated while in other it is branched and may contains double or triple bonds. A few fatty acids contain 3 carbon ring, hydroxyl group or methyl group branch.

 Types of fatty acid:

1. Saturated fatty acid
2. Unsaturated fatty acid
3. Hydroxyl fatty acid
4. Cyclic fatty acid

1. Saturated fatty acid:

• General formula: CnH2n+1COOH
• These Fatty acids do not have double or triple bond in the hydrocarbon chain.
• Saturated FA containing even number of carbon atom are more common.

On the basis of chain length, saturated fatty acids are further classified as

1. Short chain fatty acid: less than 6 carbon atom
2. Medium chain fatty acid: C8 to C 14
3. Long chain fatty acid: C16 to C24 or more

 Examples of saturated fatty acids:

• Butyric acid: CH3(CH2)2COOH
• Caproic acid: CH3(CH2)4COOH
• Caprylic acid: CH3(CH2)6COOH
• Myristic acid: CH3(CH2)12COOH
• Palmitic acid: CH3(CH2)14COOH
• Stearic acid: CH3(CH2)16COOH
• Arachidic acid: CH3(CH2)18COOH
• Docosanoic acid (Behenic aid): CH3(CH2)20COOH
• N-tetraCosanoic acid (lignoceric acid): CH3(CH2)22COOH
• Cerotic acid: CH3(CH2)24COOH

**Some saturated fatty acids have branched hydrocarbon end. Eg. Isopalmitic acid and Tuberculosteric acid.

2.Unsaturated fatty acid:

• These fatty acids contain either one or more double bond or triple bond in hydrocarbon chain.

Types of unsaturated fatty acids:

i. Monounsaturated fatty acid:

• Also known as monoethenoid fatty acid
• General formula: CnH2n-1COOH
• Example: palmitoleic acid, Oleic acid

ii. Diunsaturated fatty acid:

• Also known as diethenoid fatty acid
• General formula: CnH2n-3COOH
• Examples: Linoleic acid

iii. Polyunsaturated fatty acid (PUFA)

• Examples: Linolenic acid. Arachidonic acid

iv. Triple bond containing fatty acid:

• Examples: Nemotinic acid, Santalbic acid

3. Hydroxy fatty acid:

• The hydrocarbon chain of these fatty acid contains –OH group ( hydroxyl group)
• Examples: Cerebronic acid

4. Cyclic fatty acid:

• The hydrocarbon chain of these fatty acid contains carbon ring.
• Examples: Chaulomoogric acid, lactobacillic acid

Fatty acids: Definition and Types of fatty acid

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