Water, concentration and equilibrium constants

• Organic chemistry

  Nearly all the molecules which cells use to function are carbon based (DNA, protein, carbohydrate...)
• Carbon


  • Unique ability to form chains which are stable to air and water
  • Bonds to 4 other atoms (1s2, 2s2, 2p2 - it needs to share 4 electrons from elsewhere)
  • Tetravalent
• Carbon compounds (organic chemistry) are nearly all the molecules which cells use to function
• Functional groups


  Groups which are, or contain, atoms other than C
• Functional groups

  • -OH (Hydroxyl)
  • -NH2 (Amino)
  • -SH (Sulphhydryl)
  • C=O (Carbonyl)
  • COOH (Carboxyl)
  • O-P-O-H (Phosphate)
• Hydroxyl (-OH)

  Alcohols, form hydrogen bonds by donation or acceptance of H+, fully protonated at pH7
• Amino (-NH2)


  Amines, basic, e.g. amino acids like glycine
• Sulphhydryl (-SH)


  Thiols, common in proteins, form disulphide bridges
• Carboxyl (COOH)


  Carboxylic acids, fully dissociated at pH7
• Phosphate (O-P-O-H)


  Derivatives of phosphoric acid, 1, 2 or 3 OH groups can be replaced by -OR giving phosphate esters
• Isomers


  Organic molecules with the same number of atoms of the same elements but different structures
• Types of isomerism

  • Structural
  • Geometric
  • Enantiomers
• Structural isomers

  Differ in covalent partners
• Geometric isomers


  Differ in arrangement around a double bond
• Enantiomers


  Molecules which differ only in spatial arrangement of groups around a central 'asymmetric' (chiral) carbon atom, mirror images that cannot be superimposed
• Enantiomers have identical physical and chemical properties, but differ in the way they interact with other optically active compounds