Questions
3–5 questions per exam
Difficulty
Medium
Importance
Core — never skip
Overview
Biomolecules are the fundamental chemical building blocks of living organisms, essential for understanding metabolic processes and cellular function. This topic is high-yield for CBSE/NCERT examinations, focusing on the structural complexity and specific biological roles of macromolecules. Mastering this unit requires a firm grasp on the classification of these molecules and their catalytic mechanisms.
Carbohydrates & Proteins
Carbohydrates are polyhydroxy aldehydes or ketones, classified as monosaccharides, disaccharides, or polysaccharides. Proteins are complex polymers of alpha-amino acids linked by peptide bonds, essential for structural and functional biological roles.
- Glucose is the primary hexose sugar.
- Starch (amylose and amylopectin) and Cellulose are key polysaccharides.
- Peptide bond is formed by the dehydration synthesis between amino and carboxyl groups.
- Primary, secondary, tertiary, and quaternary protein structures.
- Denaturation disrupts secondary and tertiary protein structures.
Enzymes
Enzymes are biocatalysts that accelerate chemical reactions by lowering the activation energy without altering the equilibrium constant. They are highly specific, typically proteinaceous in nature, and function optimally under specific physiological conditions.
- Lock and key model vs. Induced fit model.
- Co-factors and co-enzymes as non-protein components.
- Enzyme activity is affected by temperature and pH.
- Michaelis-Menten constant (Km) indicates affinity.
- Competitive and non-competitive inhibition mechanisms.
Nucleic Acids
Nucleic acids, specifically DNA and RNA, are polymers of nucleotides responsible for storing and transferring genetic information. Understanding the pairing rules and structural differences between these molecules is crucial for molecular biology questions.
- Composition: Nitrogenous base + Pentose sugar + Phosphate group.
- Purines (Adenine, Guanine) and Pyrimidines (Cytosine, Thymine/Uracil).
- DNA double helix structure held by hydrogen bonding.
- Chargaff's Rule: [A]=[T] and [G]=[C].
- Ribose in RNA vs. Deoxyribose in DNA.
Formula Sheet
Chargaff's Rule: A+G = T+C
Peptide Bond: -CO-NH- formation
Exam Tip
Focus on the structural differences between amylose and amylopectin, and the specific base pairing rules in DNA, as these are frequently tested in objective and short-answer sections.
Common Mistakes
- Confusing glycosidic linkages in carbohydrates with peptide bonds in proteins.
- Neglecting the role of metal ions as co-factors in enzymatic catalysis.
- Misidentifying the sugar component differences between DNA and RNA.
More Revision Notes
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