Protein structure

Primary structure

Sequence of amino acids in a polypeptide chain held together by peptide bonds

Secondary structure

Basic level of protein folding were hydrogen bonds are established between amino groups and carboxyl groups

Tertiary structure

Next level of folding where alpha helices and beta pleated sheets can be established by the formation of hydrogen bonds, ionic bonds and covalent bonds which are covalent bonds between amino acids containing the element sulfur in their R group 

Quaternary structure 

Exists for proteins where there is more than one polypeptide associated to each other 

Describe how a quaternary protein is formed from its monomers

Primary structure of proteins is a sequence of amino acids joined together by peptide bonds by condensation reaction

Second structure hydrogen bonds are established between amino groups and carboxyl groups

Tertiary structure formed by interactions between R groups

Quaternary structure contains >1 polypeptide

Importance of the primary structure

If even one amino acid in the sequence is different then it will cause the ionic/ hydrogen/ disulfide bonds to form in a different location - this results in a different 3D shape

Impact: Enzymes will have a different shape active site (will be non- functioning)

Carrier proteins will have a different- shaped binding site (molecules no longer complementary and cannot be transported across membranes)

Test for proteins

Add biuret

A positive test/ observation = solution turns from blue to purple