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 BIOCHEMISTRY NOTES FOR STANDARD LEVEL

Recommended units and SI units
  • Distance (m); mass (kg); time (s, min, h, day, month or a);
  • temperature (°C, rarely K in biology);
  • volume (cm3 or dm3 );
  • amount of substance (mol); force (N); pressure (Pa or atmospheres or mm Hg); potential difference (v); energy (J or cal); power (work) (W); illumination (lx)
    •

    Chemical terms to know

    • atom – the smallest part of an element
    • molecule – the smallest particle of a substance which can exist in a free state (e.g. O2).
    • compound – a molecule or particle made of different elements (e.g. H2O)
    • element – a type of atom, a substance which cannot be further divided by chemical methods e.g. oxygen
    • electromagnetic spectrum – waves of energy (e.g. light rays, UV & infra red radiation)
    • electron (e-), proton (H+), ion (a charged particle), cation (a positively charged particle e.g. Na+ or Ca2+), anion (a negatively charged particle e.g. Cl- or NO3-),
    • solution = solute (substance: solid, liquid or gas) + solvent (liquid).
    • hydrophobic – repelled by water,  hydrophilic – attracted to water.
    • suspension – very small solid particles dispersed in a liquid.
    • sediment – solid particles which settle to the bottom of a liquid.
    • precipitate – a solid produced from a reaction in a solution.
    • diffusion – the movement of molecules from an area of high concentration to an area of low concentration.
    • dialysis – selective diffusion of particles through a partially permeable membrane.
    • osmosis – the movement of water across a partially permeable membrane from a region of high solute concentration to a region of low solute concentration.
    • covalent bond – a strong bond formed by the sharing of electrons between two atoms e.g. the peptide bond between amino acids.
    • hydrogen bonding – a weak bond between hydrogen and a negative element e.g. between hydrogens and oxygens of different water molecules,
    •  hydrolysis – the breaking of a covalent bond between two organic molecules using water (NB not dissolving in water)
    • condensation – the formation of a strong covalent bond between two organic molecules releasing water.

    Elements of biological importance

    • H, O, C, are the most common.
    • N, S, P are also important as well as the metals Na, Ca, and Fe.
    • H, O, C, N, S and P form covalent bonds (single, double or triple
      e.g. –C-C-,  -C=O,  –CN).
    • H, O, C, N, S and P are light.
    • H, O, C, N, S and P very reactive.
    • H, O, C, N, S and P produce diverse compounds which are reduced (readily oxidised).

    CARBON

    Tetravalent 4 different bonds variety isomerism.

    Forms long chains (polymers) macromolecules and ring structures.

    Tetrahedral structure 3 D variation optical isomerism.

    Organic compounds

    • Compounds containing carbon found in living organisms.
    • Not including carbonates, hydrogen carbonates, CO2 or CO.
    • Often based upon a skeleton of carbon.
    • An infinite variety possible.
    • Evolution has chosen a few for use in living organisms.
    • There are four principal groups: sugars, fatty acids, amino acids and nucleotides

    © Paul Billiet 2008