Biomolecules

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2. LÏPÏDS

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Water insoluble and simple fatty acids.

(AIPMT 2012)

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A fatty acid has a carboxyl group attached to an R group. The R group

could be a methyl or ethyl or higher number of -CH2 groups.

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E.g. Palmitic acid has 16 carbon atoms (CH3–(CH2)14–COOH or C15H31–

COOH) and Arachidonic acid has 20 carbon atoms.

FÅTTÝ ÅÇÏDS ÅRË ØF 2 TÝPËS

01

Saturated fatty acids: They have no double or triple

bonds between carbon atoms. E.g. Palmitic acid,

Stearic acid (C17H35COOH) etc.

02

Unsaturated Fatty acids: They have one or more

C = C or C ≡ C E.g. Oleic acid (C17H33COOH),

Arachidonic acid (C19H31COOH) etc.

TÝPËS ØF LÏPÏDS:

a.

Simple Lipids: These are formed of fatty acids and alcohol such as

glycerol.

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Structure of glycerol (trihydroxy propane):

CH2-OH

CH-OH

CH2-OH

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Fatty acids are esterified with glycerol through ester bond forming

monoglycerides, diglycerides & triglycerides.

1 glycerol + 1 fatty acid = Monoglyceride

1 glycerol + 2 fatty acid = Diglyceride

1 glycerol + 3 fatty acid = Triglyceride

(NEET 2016)

Based on melting point, lipids are of 2 types:

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Fats: Higher melting point.

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Oils: Lower melting point. (Eg. Gingelly oil)

b.

Compound lipids: These are the esters of fatty acids and alcohol with

additional groups. E.g. Phospholipids (fatty acids + glycerol + phosphate).

They are found in cell membranes. E.g. Lecithin.

(AIPMT 2012)