The Chemical Basis of Life II: Organic Molecules

Fats and Phospholipids

  • Composition: 1 Glycerol, 2 Fatty Acids, 1 Phosphate Group

  • Amphipathic Molecule: Polar (hydrophilic) head and nonpolar (hydrophobic) tails

  • Function: Essential for cell membrane and sub-cellular compartments formation.

Proteins

  • Composition: Carbon, Hydrogen, Oxygen, Nitrogen, and Sulfur

  • Building Blocks: 20 amino acids with a common structure and variable side chain, determining function and structure.

  • Role: Make up about half the dry weight of cells; diverse functions including enzymes, structural components, and transporters.

  • Protein Formation: Amino acids joined via peptide bonds; polypeptides can consist of one or more amino acid chains.

Protein Structure Levels

  1. Primary: Amino acid sequence.

  2. Secondary: Folding patterns (α helices, β sheets).

  3. Tertiary: 3-D shape from folding.

  4. Quaternary: Interaction of multiple polypeptides.

Folding and Stability Factors

  • Hydrogen Bonds: Between atoms in backbone/side chains.

  • Ionic Bonds: Between charged side chains.

  • Hydrophobic Effects: Nonpolar amino acids avoid water.

  • Van der Waals Forces: Attraction between atoms at optimal distances.

  • Disulfide Bridges: Formed between cysteine side chains.

Nucleic Acids

  • Types: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).

  • Nucleotide Composition: Phosphate group, 5-carbon sugar, nitrogenous base.

  • Base Pairing: A=T (2 H-bonds), G=C (3 H-bonds); DNA structure: double helix with a sugar-phosphate backbone.