Chapter 14: Macromolecules

Macromolecules: Large molecules built from small repeating units called monomers. Staudinger introduced the concept.

• Classification:
  • Structure: Linear, Branched, Cross-linked.
  • Properties: Thermoplastic (softens on heating, reversible), Thermosetting (hardens on heating, irreversible).
  • Mechanism:
    • Addition Polymerization: Monomers add up without elimination (e.g., Polyethylene, Polystyrene, PVC). Free radical mechanism (Initiation, Propagation, Termination).
    • Condensation Polymerization: Monomers combine with elimination of small molecules like H2O (e.g., Nylon 6,6, Polyester).

• Polyvinyl Chloride (PVC): Polymer of Vinyl Chloride. Used in pipes, floor coverings.
• Polystyrene: Polymer of Styrene. Used in food containers, packing material.
• Polyvinyl Acetate (PVA): Polymer of Vinyl Acetate. Used as adhesive (binder) and in chewing gums.
• Acrylic Resins: Polymers of acrylic acid/methacrylic acid. Used in plastics, paints.
• Polyester: Condensation of alcohol (Ethylene Glycol) and acid (Terephthalic acid). Used in textiles (Terylene).
• Polyamide (Nylon 6,6): Condensation of Adipic Acid (6C) and Hexamethylenediamine (6C). Textile fiber, high strength.
• Epoxy Resins: Condensation of Epichlorohydrin and Diphenylolpropane. Used as adhesive (Araldite).

Polyhydroxy aldehydes or ketones. General formula C_x(H₂O)_y.

• Monosaccharides: Cannot be hydrolyzed. (e.g., Glucose, Fructose - C6H12O6). Glucose is Aldohexose, Fructose is Ketohexose.
• Oligosaccharides: Give 2-9 monosaccharides on hydrolysis. (e.g., Sucrose = Glucose + Fructose; Maltose, Lactose). Linked by Glycosidic linkage.
• Polysaccharides: Give many units. (e.g., Starch, Cellulose, Glycogen).
  • Starch: Polymer of alpha-D-Glucose. Food entry (Amylose - soluble, blue with Iodine; Amylopectin - insoluble, no color with Iodine).
  • Cellulose: Polymer of beta-D-Glucose. Structural material (Cell wall). Human cannot digest (lack cellulase).
  • Glycogen: Animal starch. Stored in liver/muscles.

Polymers of Amino Acids linked by Peptide bonds (-CO-NH-).

• Classification:
  • Simple: Yield only amino acids (Albumin, Globulin).
  • Conjugated: Protein + Non-protein part (Prosthetic group). e.g., Nucleoproteins, Lipoproteins.
  • Derived: Hydrolytic products (Peptones).
• Structure: Primary (Sequence), Secondary (Helix/Sheet), Tertiary (3D folding), Quaternary (Multiple chains).
• Denaturation: Loss of structure/activity by heat/pH (e.g., coagulation of egg white).

Heterogeneous organics soluble in organic solvents, insoluble in water.

• Fats/Oils: Esters of Glycerol and Fatty Acids (Triglycerides). Fats are saturated (solid), Oils are unsaturated (liquid).
• Reactions:
  • Saponification: Hydrolysis with alkali -> Soap + Glycerol.
  • Hardening: Hydrogenation of oils -> Fats (Vegetable Ghee).
  • Rancidity: Foul smell due to oxidation/hydrolysis.
• Characterization:
  • Acid Number: mg KOH to neutralize free acid in 1g fat.
  • Saponification Number: mg KOH to saponify 1g fat.
  • Iodine Number: g Iodine absorbed by 100g fat (Measure of unsaturation).

Enzymes

Biological catalysts (Proteins). Specific in action. Factors: Temp (Optimum 37°C), pH, Concentration. Enzyme + Co-factor (non-protein) = Holoenzyme.

Nucleic Acids

Polymers of Nucleotides (Base + Sugar + Phosphate).

• DNA (Deoxyribonucleic Acid): Deoxyribose sugar. Bases: A, G, C, Thymine. Double Helix (Watson & Crick). Heredity info.
• RNA (Ribonucleic Acid): Ribose sugar. Bases: A, G, C, Uracil. Single strand. Protein synthesis.