Biological compounds

• Water


  A polar molecule which allows hydrogen bonds between molecules giving water important properties
• Properties of water


  • Solvent
  • Metabolite
  • High specific heat capacity
  • High latent heat of vaporisation
  • Surface tension
• Solvent


  Polar molecules dissolve in water and are able to be transported
• Metabolite


  Water is a reactant in photosynthesis and hydrolysis, produced in aerobic respiration and condensation reactions
• High specific heat capacity


  A lot of energy is required to change the temperature of water so aquatic/cellular environments remain stable
• High latent heat of vaporisation

  Evaporative cooling
• Surface tension


  Support and buoyancy
• Hydrogen bonds
• Carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  Triose (3C)

  Pentose (5C)

  Hexose (6C)
• Hexose


  • Glucose
• Monosaccharides


  Monomers that are linked to make dimers and polymers
• Isomers of glucose


  • Alpha-glucose

  Beta-glucose
• Disaccharides


  Sucrose (glucose and fructose)

  Maltose (alpha-glucose and alpha-glucose)

  Lactose (glucose and galactose)
• Polysaccharides


  Starch (polymer of alpha-glucose)

  Glycogen (polymer of alpha-glucose)

  Cellulose (polymer of beta-glucose)

  Chitin (as cellulose but with some -OH groups replaced by nitrogen-containing acetylamine groups)
• Amino acid


  The general form has an amino (basic) group, a carboxyl (acid) group, and a variable R group
• Dipeptide


  Two amino acids linked together
• Polypeptide


  A polymer of amino acids
• Protein structure


  • Primary (sequence of amino acids)

  Secondary (alpha helix or beta pleated sheet)

  Tertiary (folded structure)

  Quaternary (more than one polypeptide chain)
• Protein types

  • Fibrous (structural function)

  Globular (metabolic function)
• Biuret test


  Tests for proteins, gives a purple/violet colour
• Inorganic ions


  • Magnesium

  Iron

  Phosphate

  Calcium
• Triglyceride


  Glycerol linked to 3 fatty acid chains during condensation reactions forming ester bonds
• Phospholipid

  Glycerol linked to 2 fatty acid chains and a phosphate molecule, with a hydrophilic head and hydrophobic tail
• Lipid test

  Mix with absolute ethanol then add equal volumes of water, positive result is a cloudy emulsion
• Functions of lipids


  • Insulation

  Energy storage

  Protection
• Saturated fatty acids


  Have only single carbon-to-carbon bonds
• Unsaturated fatty acids

  Mono-unsaturated have one carbon-to-carbon double bond, poly-unsaturated have two or more carbon-to-carbon double bonds
• High intake of saturated fats is a contributory factor in heart disease as it raises the low-density lipoprotein (LDL) cholesterol level, which increases the incidence of atheromas in coronary arteries
• Starch test


  Iodine solution gives a blue/black colour
• Reducing sugar test

  Benedict's reagent gives a colour change from blue to indicate the amount of reducing sugar present
• Non-reducing sugars must be hydrolysed by boiling in hydrochloric acid first for the reducing sugar test to work
• The primary structure of a protein refers to its sequence of amino acids.
• Protein synthesis is the process by which amino acids join together to form polypeptide chains, which then fold into specific shapes to create functional proteins.
• Amino acids are the building blocks of proteins.