Biomolecules Chapter Explained for Board Exams: Complete Study Notes 2026
- Swarangi Nawge
- 21 hours ago
- 3 min read
1. Chapter Overview & Marks Distribution 2026
According to the latest 2026 CBSE & State Board guidelines, the Biomolecules chapter remains a high-scoring unit in the Organic Chemistry section.
Theory Weightage: 7 Marks
Difficulty Level: Easy to Moderate
Focus Areas: Chemical reactions of glucose, protein structures, vitamin deficiencies
2. Carbohydrates: The Fuel of Life
Carbohydrates are optically active polyhydroxy aldehydes or ketones.
Important Chemical Reactions of Glucose
Board exams frequently ask for evidence of the structure of glucose. The following reactions must be memorized:
Observation | Reactant / Reagent | Evidence |
Straight Chain | HI / Heat | Presence of six carbon atoms in a row |
Carbonyl Group | NH₂OH (Hydroxylamine) | Formation of oxime |
Aldehydic Group | Bromine water (mild oxidation) | Formation of gluconic acid |
Primary Alcohol | HNO₃ (strong oxidation) | Formation of saccharic acid |
Pro-Tip:Sucrose is a non-reducing sugar because its reducing groups (aldehydic and ketonic) are involved in glycosidic linkage.
3. Proteins: Building Blocks and Zwitterions
Proteins are polymers of alpha-amino acids. In 2026, application-based questions on denaturation are highly expected.
The Zwitterion Concept
In an aqueous solution:
The carboxyl group loses a proton
The amino group gains a proton
This results in a dipolar ion called a zwitterion:
R–CH(NH₂)–COOH ⇌ R–CH(NH₃⁺)–COO⁻
Fibrous vs Globular Proteins
Feature | Fibrous Proteins | Globular Proteins |
Shape | Fiber-like, linear | Spherical, folded |
Solubility | Insoluble in water | Soluble in water |
Examples | Keratin (hair), Myosin | Insulin, Albumin |
4. Nucleic Acids: DNA vs RNA
Nucleic acids are long-chain polymers of nucleotides.
Nucleoside = Nitrogen base + Sugar
Nucleotide = Nitrogen base + Sugar + Phosphate
Linkage:Nucleotides are joined by phosphodiester linkage between the 5′ and 3′ carbon atoms of the pentose sugar.
5. Vitamins & Health Significance
Vitamins are classified based on solubility, a favorite topic for 1-mark board questions.
Fat-Soluble Vitamins: A, D, E, K
Stored in liver and adipose tissue
Water-Soluble Vitamins: B-complex and C
Must be supplied regularly as they are excreted in urine
6. Biomolecules Medical Relevance 2026
The 2026 curriculum emphasizes the medical applications of biomolecules:
Glycomics in Cancer:Study of carbohydrate chains on cell surfaces to detect early-stage tumors
mRNA Therapeutics:Understanding RNA structure enabled rapid development of specialized vaccines
Protein Folding Diseases:Research on misfolded proteins is helping treat Alzheimer’s and Parkinson’s disease
7. Most Repeated Board Exam Questions (PYQs)
Based on official CBSE, ISC, and UP Board papers (2018–2025):
Why is Vitamin C not stored in the human body? (Repeated 5 times)
Define Inversion of Sugar. (Repeated 4 times)
Difference between a nucleoside and a nucleotide? (Repeated 6 times)
Explain the primary and secondary structure of proteins. (Repeated 7 times)
What happens when D-glucose is treated with HNO₃? (Repeated 3 times)
8. Frequently Asked Questions (FAQs)
Q1. How can I prepare the Biomolecules Chapter Explained for Board Exams quickly?
Answer:Focus on summary tables for vitamins and specific chemical tests of glucose. Use mnemonics for amino acids and base pairing:A–T and G–C.
Q2. What is a peptide linkage?
Answer:A peptide linkage is an amide bond (–CO–NH–) formed between:
the –COOH group of one amino acid
the –NH₂ group of another amino acid
Q3. Is the 2026 syllabus different for Biomolecules?
Answer:The core concepts remain the same, but there is a 20% increase in case-based questions involving real-life medical scenarios.
Conclusion
Mastering the Biomolecules Chapter Explained for Board Exams is essential for securing high marks in 2026. By focusing on the structural differences in carbohydrates, the Zwitterionic nature of proteins, and the medical significance of nucleic acids, you align your preparation with both the NCERT syllabus and modern medical trends. Consistent revision of these "Easy Notes" will ensure you are fully prepared for both theoretical and application-based board questions.
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