Lecture Notes on Chemical Composition of Living Organisms

1. Composition of Living Organisms

• Living organisms are composed of chemicals (elements and compounds).
• Elemental Analysis: Determines elemental composition in living tissues.
  • Common elements: carbon, hydrogen, oxygen (also found in Earth's crust).
  • Higher concentration in living organisms.

2. Chemical Analysis of Organic Compounds

• To analyze organic compounds:

  1. Grind tissue in trichloroacetic acid to make a slurry.
  2. Strain through cheesecloth:
     • Filtrate (acid soluble pool): contains organic compounds.
     • Retentate (acid insoluble fraction).

• Separation Techniques: Chromatography, centrifugation to isolate compounds.

• Biomolecules: Carbon compounds from living tissues (e.g., carbohydrates, lipids, amino acids, nucleic acids).

  • Metabolites: Intermediates/products of metabolism (primary and secondary).
  • Primary Metabolites: Essential for growth (e.g., amino acids, sugars).
  • Secondary Metabolites: Ecological function (e.g., alkaloids, pigments).

3. Inorganic Compounds Analysis

• Inorganic compounds (e.g., NaCl, CaCO3).
• Analysis process:
  1. Weigh fresh leaf (wet weight).
  2. Dry leaf (dry weight).
  3. Burn leaf: carbon oxidizes, releases CO2 and water; ash contains inorganic elements.

4. Functional Groups in Biomolecules

• Functional groups contribute to biomolecule formation.
• Amino Acids: Building blocks of proteins.
  • Contains amino and carboxyl groups on the same carbon (alpha carbon).
  • 20 Standard Amino Acids: Example - Glycine (H), Alanine (methyl), Serine (hydroxymethyl).
  • Properties: Acidic (e.g., glutamic acid), basic (e.g., lysine), neutral (e.g., valine).

5. Lipids and Fatty Acids

• Fatty acids form lipids (fats, oils).
• Composition: Carboxyl group + R group (variable).
  • Saturated (no double bonds) vs. unsaturated (one or more double bonds).
  • Glycerides: Formed from glycerol + fatty acids (mono-, di-, triglycerides).
• Phospholipids: Contain phosphorus, found in cell membranes.

6. Nucleic Acids

• Nucleotides: Building blocks of nucleic acids (DNA/RNA).
  • Components: Heterocyclic compound (base), monosaccharide (sugar), phosphoric acid.
  • Nitrogenous Bases: Purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil).
  • DNA: Contains deoxyribose; RNA: Contains ribose.

7. Biomolecules Classification

• Biomicromolecules: Small molecular weight (18-800 Daltons).

  • Examples: Water, minerals, amino acids, sugars, lipids, nucleotides.

• Biomacromolecules: Larger molecular weight (10,000+ Daltons).

  • Examples: Proteins, polysaccharides, nucleic acids.

8. Protein Structure

• Proteins: Polymers of amino acids linked by peptide bonds.
  • Levels of Structure:
    1. Primary: Sequence of amino acids.
    2. Secondary: Local folding (alpha helices, beta sheets).
    3. Tertiary: Overall 3D shape.
    4. Quaternary: Multiple polypeptide chains (subunits).
• Examples of proteins: Collagen, rubisco, trypsin, insulin, antibodies, GLUT4.

9. Bonding in Biomolecules

• Polymers: Formed by monomers bonding (e.g., polyethylene).
• Bond Types:
  • Peptide Bonds: In proteins (carboxyl reacts with amino group, dehydration).
  • Glycosidic Bonds: In polysaccharides (dehydration between monosaccharides).
  • Phosphodiester Bonds: In nucleic acids (sugar-phosphate backbone).

10. DNA Structure

• B-DNA: Double helix structure, anti-parallel strands.
  • 4 bases: A, T, C, G (pairing rules: A-T, C-G).
  • Features:
    • Pitch: 34 angstroms.
    • Rise per base pair: 3.4 angstroms.

Conclusion

• Understanding the chemical composition and structure of biomolecules is crucial for studying life processes and functions in living organisms.