Take timed practice tests on Biomolecules and Polymers for JEE Main and JEE Advanced with session-wise drills, score review, and explanation-led revision.
Six 20-question timed sessions plus a 60-question chapter module. Each item is original and reframed for copyright safety.
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1. Glucose (C₆H₁₂O₆) is classified as a:
Explanation: Glucose is a monosaccharide with 6 carbons (hexose) and an aldehyde group (aldohexose). It exists in open-chain form (Fisher projection) and cyclic forms (α and β pyranose — Haworth projections).
2. Amino acids are the building blocks of proteins. They contain both:
Explanation: An α-amino acid has NH₂ and COOH groups on the same carbon (α-carbon). At physiological pH, they exist as zwitterions (NH₃⁺/COO⁻). Essential amino acids cannot be synthesised by the body.
3. DNA contains the base pairs:
Explanation: Watson-Crick base pairing in DNA: A pairs with T (2 H-bonds), G pairs with C (3 H-bonds). In RNA, T is replaced by U (uracil). The complementary base pairs hold the double helix together.
4. The peptide bond (−CO−NH−) forms between:
Explanation: Peptide bond formation (condensation): −COOH + H₂N− → −CO−NH− + H₂O. The peptide bond has partial double bond character (resonance) and is planar → proteins have defined secondary structures (α-helix, β-sheet).
5. Enzymes are biological catalysts that:
Explanation: Enzymes are proteins (mostly) that catalyse specific biochemical reactions. They lower Ea without being consumed. Substrate fits the active site (lock-and-key: rigid fit; induced-fit: active site adapts). Optimum pH and temperature specific to each enzyme.
6. Vitamin C (ascorbic acid) deficiency causes:
Explanation: Deficiency diseases: Vit C → Scurvy. Vit D → Rickets. Vit B₁ (thiamine) → Beriberi. Vit A → Night blindness. Vit B₁₂ → Pernicious anaemia. Vit K → impaired blood clotting.
7. Nylon-6,6 is prepared from:
Explanation: Nylon-6,6: condensation polymer of hexamethylenediamine (H₂N(CH₂)₆NH₂) and adipic acid (HOOC(CH₂)₄COOH) with loss of water. 6,6 refers to 6 carbons in each monomer. Nylon-6 is from caprolactam alone.
8. Bakelite (phenol-formaldehyde resin) is a:
Explanation: Bakelite is a thermosetting polymer — once set, it cannot be softened or remoulded by heating (unlike thermoplastics). The extensive cross-linking between chains creates a rigid, hard, infusible network. Used in electrical switches, handles.
9. Starch and cellulose are both polymers of glucose but differ in:
Explanation: Both are glucose polymers (C₆H₁₀O₅)ₙ. Starch: α-1,4 glycosidic bonds (humans can digest). Cellulose: β-1,4 glycosidic bonds (humans cannot digest — no cellulase enzyme). The different bond geometry causes helical (starch) vs linear (cellulose) structures.
10. The number of chiral centres in glucose (open-chain aldohexose) is:
Explanation: Open-chain glucose: CHO−CH(OH)−CH(OH)−CH(OH)−CH(OH)−CH₂OH. Carbons 2, 3, 4, 5 each have 4 different substituents → 4 chiral centres. Maximum stereoisomers = 2⁴ = 16 (8 pairs of enantiomers, 8 D-aldohexoses and 8 L-aldohexoses).
11. Sucrose is a disaccharide of:
Explanation: Sucrose (table sugar) = glucose (α-1) + fructose (β-2) linked by a 1,2-glycosidic bond. It is non-reducing (no free anomeric OH). Lactose = glucose + galactose. Maltose = glucose + glucose.
12. Natural rubber is a polymer of:
Explanation: Natural rubber = cis-polyisoprene (isoprene monomer: CH₂=C(CH₃)−CH=CH₂). Vulcanisation with sulphur cross-links chains, improving elasticity and strength. Gutta-percha is trans-polyisoprene (hard, non-elastic).
13. A Zwitter ion (amphoteric species) of an amino acid forms at:
Explanation: At the isoelectric point (pI), an amino acid exists predominantly as the zwitterion (NH₃⁺/COO⁻) with zero net charge. Below pI: cationic (NH₃⁺/COOH). Above pI: anionic (NH₂/COO⁻). Zwitterions have minimum solubility at pI.