Proteins

Proteins:
Amino acids are the monomer units that are linked to from polymer units called polypeptides. Polypeptides can be combined to form proteins. Amino acids are linked by peptide bonds.
Two monomers can be joined together to form dipeptides. The process is pretty much the same as a monosaccharide making a disaccharide; a condensation reaction, where a water molecule is taken out between them, only it is joined by the carbon and nitrogen joining together, and this is called a dipeptide bond.
After a series of condensation reactions, a polypeptide chain is formed. (100’s of amino acids joined up together.)
The amino acid sequence defines the shape, so a change in this could stop it carrying out it’s function.
The secondary structure is formed by hydrogen bonds forming between the N-H, and C-O as they have opposite charges. This twists the chain into a 3D shape; such as the alpha helix.
The tertiary structure is formed by the bending and twisting of the polypeptide helix into a more compact shape, all three types of bonding, disulfide, hydrogen and ionic, take part in holding the shape together.
The quaternary structure is formed by several polypeptide chains and prosthetic groups joining together into one complex molecule.
The test for proteins is the Biuret test. You place a sample of the solution with equal volumes of Sodium Hydroxide into a test tube. You then add a few drops of copper sulphate, and mix. A purple colouration indicates the presence of peptide bonds, and therefore, a protein. Without, it stays blue.
1) Dipeptide bonds link amino acids together.
2) A condensation reaction is involved in linking amino acids together.
3) The four different components of an amino acid are: An amino group, a carboxyl group, a hydrogen atom, and a functional ‘R’ group.