Question

Following are the statements with reference to 'lipids'.

(a) Lipids having only single bonds are called unsaturated fatty acids
(b) Lecithin is a phospholipid
(c) Trihydroxy propane is glycerol
(d) Palmitic acid has 20 carbon atoms including carboxyl carbon

Choose the correct answer from the options given below.

• A. (b) and (d) only
• B. (a) and (b) only
• C. (c) and (d) only
• D. (b) and (c) only

Answer 1

The correct option is D (b) and (c) only

Lipids could be simple fatty acids. Fatty acids have a carboxyl group (–COOH) attached to an R group which could be a methyl or ethyl or higher number of –CH2 groups.

The fatty acid, palmitic acid, has 16 carbons including carboxyl carbon.

Hence, statement d is incorrect.

Fatty acids can be saturated or unsaturated.

Saturated fatty acids have single bonds between the carbon atoms and unsaturated fatty acids are those that have double bonds between the carbon atoms.

Hence, statement a is incorrect.

Another simple lipid is glycerol. Glycerol is an alcohol with three carbon atoms, five hydrogen atoms and three hydroxyl groups. Because of the presence of three hydroxyl groups, it is called trihydroxy. Propane is a three-carbon alkane with the molecular formula C₃H₈. When three hydrogen atoms of propane are replaced by three hydroxyl groups, this gives rise to a molecule of glycerol.


Hence, statement c is correct.

Lecithin is a phospholipid composed of phosphoric acid, cholines, esters of glycerol, and two fatty acids. These are found in cell membranes.

Hence, statement b is correct.