Revision notes for Biology AS Unit 1 – Protein structure

How a protein’s structure relates to its function?

Primary structure of proteins

The sequence of amino acids in a polypeptide chain forms the primary structure of any protein. It is the primary structure of a protein that determines its shape and function. The protein shape is specific to its function; if just a single amino acid changes, it can change the shape of the protein and stop it from carrying out its function.


Secondary structure of proteins

Hydrogen bonds form between the amino acids in the chain. This makes the polypeptide chain coil into a 3D alpha helix shape or fold into a beta pleated sheet.


Tertiary structure of proteins

The a-helixes of the secondary structure can be coiled and folded further to form a more complex, 3D structure because more bonds form between different parts of the polypeptide chain (ionic bonds, disulphide bonds, hydrogen bonds).


Quaternary structure of proteins

Some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together.


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