Proteins - 4 structural levels

Question 1

Primary structure

Answer 1

this is the sequence of amino acids in the polypeptide chain

Question 2

Secondary structure

Answer 2

this is when hydrogen bonds form between the amino acids in the chain - making it coil into an alpha helix or fold into beta pleated sheet - this is the secondary structure

Question 3

Tertiary structure

Answer 3

the chain of amino acids coiled or folded further and more bonds form between different parts of the polypeptide chain e.g. ionic bonds.

• disulfide bridges form when 2 of the amino acids; cysteine bonds to the sulfer in another.
• for proteins which are formed by a single polypeptide chain, the tertiary structure forms its final 3D structure.

Question 4

Quaternary structure

Answer 4

• some proteins are made up of several different polypeptide chains held together by bonds - this quaternary structure is the way these polypeptide chains are assembled together.
• e.g. haemoglobin - the quaternary structure is the protiens final 3D structure.