BIOLOGICAL MOLECULES- Proteins

Role of Proteins:
-Biological activities; hormones, enzymes, antibodies, transport/carrier proteins in the cell membrane.
-Globular proteins; functional proteins e.g. enzymes, and have a spherical shape.
-Fibrous proteins; perform structural functions e.g. keratin in hair and nails, and have a long and narrow shape.

General formula of Amino Acids: NH2CHRCOOH (R is the variable group)
There are 20 types of amino acids, and when two amino acids join they form a dipeptide.

STRUCTURE
Primary:
A number and sequence of amino acids in a polypeptide chain. Molecules are held together by peptide bonds.

Secondary:
The polypeptide chain will either coil into an alpha helix or fold into a beta pleated sheet. Hydrogen bonds form between amino acids.

Tertiary:
This is the final 3D structure for a single polypeptide chain, the secondary structure is coiled/folded further into a globular shape. The molecule is held by hydrogen bonds, ionic bonds, hydrophobic interactions, and disulphide bridges.

Quaternary:
Two or more polypeptide chains in tertiary structure join together and are held by interactions.