ChemistryCHEM 14
Biomolecules & Polymers
Carbohydrates, proteins, DNA/RNA, vitamins, hormones, natural and synthetic polymers
NCERT XII Ch.14+15
NCERT Ref
Concept Core
Essential theory — everything NCERT tests on Biomolecules & Polymers
CARBOHYDRATES
Monosaccharides: glucose (C₆H₁₂O₆), fructose, galactose. Disaccharides: sucrose (glucose+fructose), maltose (glucose+glucose), lactose (glucose+galactose). Polysaccharides: starch (amylose+amylopectin), cellulose, glycogen.
Reducing sugars: all monosaccharides, maltose, lactose (free aldehyde/ketone). Non-reducing: sucrose (no free group).
PROTEINS & AMINO ACIDS
20 amino acids. Peptide bond: C(O)-NH between carboxyl and amino groups (condensation). Levels of structure: 1° (seq), 2° (α-helix/β-sheet, H-bonds), 3° (overall 3D, disulfide bonds), 4° (multiple subunits).
Essential amino acids: 9 (not synthesised by body): Val, Leu, Ile, Thr, Met, Phe, Trp, Lys, His.
NUCLEIC ACIDS
DNA: deoxyribose, A T G C. RNA: ribose, A U G C. Chargaff's rules: A=T, G=C (in DNA). A/T + G/C = 1.
Nucleoside = base + sugar. Nucleotide = base + sugar + phosphate. DNA double helix: anti-parallel, A-T (2 H-bonds), G-C (3 H-bonds).
VITAMINS & HORMONES
Fat-soluble: A, D, E, K. Water-soluble: B-complex, C.
Deficiency: A (night blindness), B₁ (Beri-beri), B₁₂ (pernicious anaemia), C (scurvy), D (rickets), K (impaired clotting).
Hormones: amino acid derivatives (adrenaline, thyroxine), peptide (insulin, glucagon), steroid (cortisol, testosterone, estrogen).
POLYMERS
Natural: starch, cellulose, rubber (polyisoprene), protein, DNA. Synthetic addition: polyethylene, PVC, teflon (PTFE), polystyrene. Condensation: nylon-6,6 (adipic acid + hexamethylenediamine), nylon-6 (caprolactam), dacron/terylene (ethylene glycol + terephthalic acid), bakelite.
Fact & Formula Vault
High-yield facts, numbers, and formulas
Reducing Sugars
All monosaccharides: reducing
Maltose: reducing
Lactose: reducing
Sucrose: NON-reducing
Cellulose, starch: non-reducing
Vitamins Quick Ref
Vitamin A: night blindness
Vitamin B₁: beriberi
Vitamin C: scurvy
Vitamin D: rickets
Vitamin K: clotting
Polymer Types
Addition: polyethylene, PVC, Teflon
Condensation: nylon-6,6, dacron
Nylon-6: caprolactam (ring opening)
Bakelite: phenol + formaldehyde
Worked Examples
NEET-style questions solved step-by-step
EASYSucrose is a non-reducing sugar because:▾
Sucrose is a non-reducing sugar because:
Sucrose (glucose + fructose) has NO free aldehyde or ketone group — both anomeric C-1 (glucose) and C-2 (fructose) are involved in glycosidic bond. So it cannot reduce Fehling's/Tollens'.
MEDIUMWhich vitamin deficiency causes scurvy?▾
Which vitamin deficiency causes scurvy?
Vitamin C (ascorbic acid). Scurvy: bleeding gums, poor wound healing, anaemia. Vitamin C is water-soluble and essential for collagen synthesis.
HARDNylon-6,6 is formed by condensation of:▾
Nylon-6,6 is formed by condensation of:
Adipic acid (hexanedioic acid) + hexamethylenediamine. The 6,6 refers to 6 carbons in each monomer. Nylon-6 is formed from caprolactam (ring-opening polymerisation).
Mistake DNA
Common NEET traps for this chapter
⚠ Reducing vs non-reducing sugars
Sucrose is the only common non-reducing disaccharide. Maltose and lactose are reducing (have free anomeric OH). All monosaccharides reduce.
✓ Fix: Sucrose = non-reducing. Maltose/Lactose = reducing.
⚠ Nylon-6 vs Nylon-6,6
Nylon-6 = caprolactam (1 monomer, ring-opening). Nylon-6,6 = adipic acid + hexamethylenediamine (2 monomers, condensation).
✓ Fix: 6 = caprolactam. 6,6 = two 6-carbon monomers.
⚠ Fat vs water-soluble vitamins
A, D, E, K = fat-soluble (stored in body, toxicity possible). B-complex, C = water-soluble (not stored, excreted in urine).
✓ Fix: ADEK = fat-soluble. BC = water-soluble.
Chapter Intelligence
Exam data and last-minute strategy
NEET Frequency
2–3 Q/year. Reducing/non-reducing sugars, vitamin deficiency diseases, Nylon-6 vs 6,6, DNA base pairing, protein structure levels.
High-Yield
Sucrose = non-reducing. ADEK = fat-soluble. Vit C = scurvy. Nylon-6,6 = adipic acid + hexamethylenediamine. DNA: A-T (2 H-bonds), G-C (3 H-bonds).
Strategy
Vitamin deficiency table: 5 rows (A/B1/C/D/K, disease). Polymer table: type, monomer, example. These cover 80% of questions in this chapter.
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