Bio-chemistry(Proteins)

• Differ from carbohydrates and lipids as in addition Carbon Hydrogen and Oxygen they contain Nitrogen.
• Built of sub-units of amino acids.
• Each protein posses an amino group NH2 and a carboxyl group -COOH and the R group

Peptide Bond

• The amino group reacts with carboxyl group of another amino acid, in a condensation reaction, elimination of water
• Peptide bond is formed
• Polypeptide is a number of amino acids joined in this way.

Protein Structure

• Primary- sequence of amino acids in the polypeptide chain, proteins differ from variety, number of the amino acids linked by peptide bonds
• Secondary- Shape of polypeptide chain as a result of hydrogen bondinge.g alpha helix beta pleeted sheet-zig zag.
• Tertiary- Bending & twisting of polypetide helix into a compact structure.Gives molecule 3D shape, mantained by disulphide, ionic and hydrogen bonds.
• Quartenary-

Fibreous Proteins

• Structural functions and consist of polypeptides in parallel chains or sheets with numerous cross-linkages to form long fibres.
• Insoluble in water, strong and tough e.g tough properties in Collagen for tendons.
• A single fibre has 3 polypetide chains twisted round each other like a rope, linked by cross-bridges making a very stable molecule.

Globular Protreins

• variety of different functions. e.g enzymes, antibodies, hormones
• Compact folded as spherical molecules
• Soluble in water
• Haemoglobin has 4 polypeptide chains at the centre an iron containing group called haem.

In plants mineral ions are transported in dissolved water,They can be divided into 2 groups:

• Macronutrients- needed in small amounts
  • Magnesium- a constiuent of chlorophyll in leaves
  • Iron- a constiuent of haemoglobin in blood
  • Phosphate found in plasma membrane, nucleic acids,atp
  • Calcium, a constituent of blood and teeth
• Micronutrients- needed in minute amounts e.g copper zinc.