Biology S6 Sem 1 Test 2

Proteins

Macromolecules made of long chains of recurring monomers called amino acids linked together by peptide bonds.

Amino acids

The organic monomer subunit that links together via peptide bonds to form polypeptides and proteins, only 20 amino acids can form polypeptides.

Amino acids functional groups

Amino acids contain an amino group and carboxyl group

Amino acid structure

Amino group, carboxyl group, Hydrogen and an R-Group (variable) attached to the alpha carbon

R-Group in amino acids

A variable group attached to the central alpha carbon atom of an amino acid, defines the structure, chemical properties and behaviour of the overall polypeptide.

Peptides

A short chain of amino acids linked together by covalent bonds.

Peptide bonds

A covalent bond between an amino end (N terminal) and a carboxyl end (C terminal) that links two amino acids together.

4 levels of Protein structures

Primary structure, Secondary structure, Tertiary structure, Quaternary structure

Primary structure

The sequence of amino acids linked together, forming a polypeptide. It is held together by covalent peptide bonds.

Secondary structure

Local regions of the resulting polypeptide can then be coiled into an α-helix or spread into a β pleated sheet. It is held together by Hydrogen bonds.

α helix

A common protein secondary structure shaped like a coiled spring, held together by regular hydrogen bonds between the C=O group of one amino acid and the N - H group of another amino acid 4 residues down the chain.

β sheet

A protein secondary structure composed of 2 or more adjacent extended polypeptide chains aligned side by side. It is stabilised by hydrogen bonds formed between the C=O group and and the N-H group of a neighbouring strand, creating a sheet-like structure with a pleated appearance.

Tertiary structure

Regions of secondary structure associated with each other in a specific manner to form the tertiary structure, which describes the final folding of the polypeptide. It is held together by hydrogen bonds, ionic bonds, Disulfide bridges, hydrophobic interactions and Van der Waals forces

Quaternary structure

The association of two or more polypeptides as they interact to form the final functional protein