NCERT Class 11-Biology Exemplar Chapter –9 Biomolecules Part 5

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Question 2:

What are different classes of enzymes? Explain any two with the type of reaction they catalyse.


Following are the different classes of enzymes:

1. Oxidoreductase

2. Transferase

3. Hydrolase

4. Lysases

5. Isomerase

6. Ligases

(a) Oxidoreductase:

These are the enzymes which help in simultaneous oxidation and reduction of two substrates.

(b) Hydrolases:

These enzymes facilitate the hydrolysis of a molecule.

Question 3:

Nucleic acids exhibit secondary structure. Describe through Wetson- Crick Model.


NA is made up of two polypeptide chains, arranged in double helix.

The backbone is of sugar phosphate while the nitrogenous bases are present on the inner side.

These nitrogenous bases pairs to each other by H bonds. These H bond confers for the stability of helix.

DNA double helix

DNA Double Helix

Question 4:

What is the difference between a nucleotide and nucleoside? Give two examples of each with their structure.


Nucleotides are the monomers of nucleic acid.

Formed of nucleoside and phosphate group.

Whereas nucleosides are the constituent of nucleotides.

Question 5:

Describe various forms of lipid with a few examples.

Lipids are classified into three categories:


1. Simple lipids: these are the esters of fatty acids.

Examples- Triglycerol, fats and wax

2. Compound lipids: lipids with an additional group other than fats and alcohol.

Example: Phospholipids, glycolipids etc.

3. Derivatives: When lipid consists of hydrocarbon rings and long chains of hydrocarbon.

Example- Steroids, cholesterol and prostaglandins.

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