Biomolecules Full Notes
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patriciathiagarajanBiomolecules Full Notes
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patriciathiagarajanBIOMOLECULES + ENZYMES – FULL DETAILED NOTES
1. INTRODUCTION
- Living organisms are made up of chemicals → biomolecules.
- Types:
• Micromolecules (<1000 Da): sugars, amino acids, nucleotides, lipids.
• Macromolecules (>1000 Da): polysaccharides, proteins, nucleic acids, complex lipids.
2. CARBOHYDRATES
Definition: Polyhydroxy aldehydes or ketones.
Classification:
a) Monosaccharides (Trioses: Glyceraldehyde; Pentoses: Ribose, Deoxyribose; Hexoses: Glucose,
Fructose, Galactose).
• Glucose: Blood sugar, dextrose, reducing sugar.
• Fructose: Fruit sugar, ketohexose, sweetest sugar.
b) Disaccharides:
• Maltose (Glu+Glu), Lactose (Glu+Gal), Sucrose (Glu+Fru – non-reducing).
c) Polysaccharides:
• Starch (amylose + amylopectin), Glycogen (animals), Cellulose (plants), Chitin (arthropods).
Functions: Energy storage, structure, recognition.
3. PROTEINS
Definition: Polymers of amino acids (20 types).
- Essential AA: Val, Leu, Ile, Lys, Met, Thr, Phe, Trp, His.
- Non-essential: Ala, Gly, Ser, Glu, Asp, etc.
Peptide bond: Between -COOH and -NH2.
Structures:
1. Primary: Linear chain.
2. Secondary: α-helix (keratin), β-sheet (fibroin).
3. Tertiary: 3D folding (disulfide, ionic, hydrophobic).
4. Quaternary: Multimeric (Hb = α2β2).
Types: Fibrous (collagen, keratin), Globular (enzymes, antibodies).
Functions: Catalytic, structural, transport, defense, hormonal.
4. NUCLEIC ACIDS
Monomer: Nucleotide = sugar + base + phosphate.
Bases: Purines (A, G), Pyrimidines (C, T, U).
DNA: Double helix, antiparallel, A=T, G≡C (Chargaff’s rule).
RNA: Single-stranded, types – mRNA, tRNA, rRNA.
Functions: Heredity, protein synthesis.
5. LIPIDS
Definition: Heterogeneous, insoluble in water, soluble in organic solvents.
Types:
- Simple: Fats (saturated), Oils (unsaturated).
- Compound: Phospholipids, Glycolipids.
- Derived: Steroids (cholesterol, hormones), Vitamins A, D, E, K, carotenoids, waxes.
Functions: Energy storage, membranes, hormones, insulation.
6. ENZYMES
Definition: Biological catalysts (mostly proteins, some ribozymes).
Properties: Specific, efficient, reusable.
Mechanism: Active site → substrate → product.
Models: Lock & Key, Induced Fit.
Kinetics:
- Vmax: Maximum velocity.
- Km: [S] at ½ Vmax, inverse of affinity.
Factors: Temperature (~37°C), pH (pepsin 2, trypsin 8), substrate conc, cofactors.
Cofactors:
- Prosthetic group (FAD), Coenzyme (NAD+, CoA), Metal activators (Zn2+, Mg2+).
Inhibition:
- Competitive: ↑Km, Vmax unchanged.
- Non-competitive: Km same, Vmax ↓.
- Irreversible: permanent (cyanide).
Classification (IUBMB):
1. Oxidoreductases.
2. Transferases.
3. Hydrolases.
4. Lyases.
5. Isomerases.
6. Ligases.
Examples: DNA polymerase, RNA polymerase, Amylase, Pepsin.
7. VITAMINS & ENZYMES
- Thiamine (B1): TPP.
- Riboflavin (B2): FAD, FMN.
- Niacin (B3): NAD+, NADP+.
- Pyridoxine (B6): PLP.
- Biotin: carboxylase cofactor.
- Vitamin K: clotting.
8. CLINICAL ASPECTS
- Diabetes mellitus: insulin defect.
- Lactose intolerance: lactase deficiency.
- PKU: phenylalanine hydroxylase defect.
- Sickle cell anemia: Hb mutation.
9. IMPORTANT DIFFERENCES
- DNA vs RNA.
- Starch vs Glycogen vs Cellulose.
- Competitive vs Non-competitive inhibition.
- Saturated vs Unsaturated fats.