Biological Molecules and Their Characteristics

Chemical Bonding

  • Chemical Bonds: Forces of attraction holding atoms in compounds.
  • Types:
    • Ionic Bonds: Formed by transfer of electrons between metals and non-metals.
    • Metals lose electrons; non-metals gain.
    • Covalent Bonds: Result from sharing electrons between non-metals.
    • Types:
      • Single: One pair of electrons (e.g. H2).
      • Double: Two pairs (e.g. O2).
      • Triple: Three pairs (e.g. N2).

Chemical Structure of Water (H2O)

  • Water Characteristics:
    • Polar molecule (partially positive and negative).
    • Universal solvent.

Effects of Hydrogen Bonding

  • Cohesion: Water molecules stick together; creates surface tension.
  • Adhesion: Water molecules bond with other substances; aids capillary action in plants.

Density of Ice and Water

  • Melting Point: 0°C.
  • Ice floats because its solid state is less dense than liquid.

Hydrogen Ion Concentration

  • pH Importance: Affects structure and activity of macromolecules; maintained stable in biological systems.
  • Buffers: Maintain constant pH conditions to ensure protein function.

Acids and Bases

  • Acids: pH < 7, higher hydronium ion concentration; may harm organisms.
  • Bases: pH > 7, lower hydronium ion concentration; strong bases can also be harmful.

Buffer Capacity

  • Buffers maintain constant pH; effectiveness depends on concentration of weak acids and bases.
  • Physiological buffers: bicarbonate, phosphate, hemoglobin, proteins.

Macromolecules

  • Types: Carbohydrates, Proteins, Lipids, Nucleic Acids.

Carbohydrates

  • Structure: (CH2O)n. 1:2:1 ratio of C-H-O; subtypes: monosaccharides, disaccharides, polysaccharides.
  • Properties: Colorless crystalline solids, sweet taste, soluble in water.

Proteins

  • Composed of amino acids; different structures (primary, secondary, tertiary, quaternary) define function.
  • Functions include structural support, transport, catalysts (enzymes), signaling.

Enzymes

  • Function: Biological catalysts, specific to substrates, lower activation energy for reactions.
  • Types: oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases.

Lipids

  • Function: Energy storage; amphiphilic (hydrophobic and hydrophilic parts).
  • Types: fats, waxes, phospholipids, lipoproteins.

Nucleic Acids

  • Involved in genetic information storage and transfer (DNA & RNA).