Biomolecules

part 1

Carbohydrates

• Classification of carbohydrates
• Monosaccharides — glucose and fructose structure
• Anomers and epimers
• Disaccharides — sucrose, maltose, lactose
• Polysaccharides — starch, cellulose, glycogen

part 2

Proteins and Enzymes

• Amino acids — structure and types
• Peptide bond formation
• Structure of proteins — primary, secondary, tertiary, quaternary
• Denaturation of proteins
• Enzymes — nature and mechanism

part 3

Vitamins, Nucleic Acids and Hormones

• Vitamins — classification and deficiency diseases
• Nucleic acids — DNA and RNA structure
• Biological functions of nucleic acids
• Hormones — types and functions

Disaccharide linkage

Sucrose: α-1,β-2 glycosidic bond (non-reducing); Maltose: α-1,4 (reducing)

★ board favourite

Peptide bond formation

−COOH + H₂N− → −CO−NH− + H₂O (condensation)

★ board favourite

DNA double helix base pairing

A−T (2 H-bonds); G−C (3 H-bonds); antiparallel strands

★ board favourite

Glucose open chain structure (aldohexose)

CHO−(CHOH)₄−CH₂OH (D-glucose)

★ frequently asked

Haworth (ring) structure of glucose

α-D-glucopyranose: −OH on C1 below ring; β: above

★ frequently asked

Amino acid general structure

H₂N−CHR−COOH (R = side chain); zwitterion at isoelectric pH

★ frequently asked

Secondary protein structure: α-helix

Intramolecular H-bonds (C=O···H−N) every 4th residue

★ frequently asked

Nucleotide = base + sugar + phosphate

Purine bases: Adenine, Guanine; Pyrimidine: Cytosine, Thymine, Uracil

★ frequently asked

Write any three reactions of glucose that establish the presence of (i) a carbonyl group, (ii) five hydroxyl groups, and (iii) a straight-chain structure.

Name one water-soluble and one fat-soluble vitamin. State one deficiency disease caused by the lack of each.

Name the two monosaccharides obtained on hydrolysis of sucrose.

Explain the terms: (i) primary structure of a protein, (ii) denaturation of protein, (iii) zwitterion. What happens to the biological activity of an enzyme on denaturation?

Define the following terms: (i) essential amino acids and (ii) peptide linkage.

(a) Define the following: (i) reducing sugars, (ii) glycosidic linkage, (iii) invert sugar. (b) Write the differences between amylose and amylopectin components of starch.

Write three points of difference between DNA and RNA.

What are anomers? Give an example.

What are enzymes? Explain how they act as biological catalysts with one example.

(i) Name the components of a nucleotide. (ii) What is the difference between a nucleoside and a nucleotide? (iii) Write the two functions of nucleic acids.

Why are amino acids amphoteric in nature?

How many marks is Biomolecules worth in the Class 12 board exam?

Around 7 marks of the 70-mark CBSE Chemistry theory paper, based on the official unit-wise weightage. Anomers of glucose and DNA/RNA structure are common.

Is Biomolecules easy or hard?

It's rated medium — a moderate-difficulty chapter in Class 12 Chemistry. Most students need about 3 hours to cover it well.

What are the important topics in Biomolecules?

The chapter covers 13 NCERT topics in 3 areas: Carbohydrates; Proteins and Enzymes; Vitamins, Nucleic Acids and Hormones.

What questions come from Biomolecules in board exams?

Between 2018–2024, CBSE board papers asked questions from this chapter on Structure of Glucose, Vitamins, Carbohydrates, Proteins — 1- to 5-mark questions.