Structure and Functions of Protein Molecules
- Organic Molecules: a) carbohydrates
- All organic molecules contain the elements C, H, O.
- Nitrogen is found in all proteins.
- Proteins are required for: a) the growth and repair of tissues
b) the production of enzymes
d) transportaion of O2 (haemoglobin)
Amino Acid Structure of Protein Molecules
There are 20 R groups which produce 20 different amino acids.<----- The general structure of an amino acid.
Synthesis of a Dipeptide
- Involves a condensation reaction... removal of a water molecule from 2 amino acid molecules.
- Results in the formation of a peptide bond between the amino group of 1 amino acid and the carboxyl group of a second amino acid.
- This is a reversible reaction... the peptide bond is broken on the addition of a water molecule --> hydrolysis.
Primary Structure of a Protein Molecule
The number and sequence of amino acids in a polypeptide chain.
Different combinations of amino acids result in the formation of different protein molecules with different functions.
Secondary Structure of a Protein Molecule
Weak H2 bonds form between the positively charged NH group and the negatively charged C=O group on either side of a peptide bond.
This results in the formation of an -helix (alpha helix).
Tertiary Structure of a Protein Molecule
The 3D shape of a protein molecule is the result of additional bonds (ionic, hydrogen, di-sulphide bridges) forming between the amino acid molecules in the polypeptide chain.
This twists and folds the protein into a unique shape.
Quaternary Structure of a Protein Molecule
A protein molecule made up of 2 or more polypeptide chains.
In a diagram it looks something like this: