Protein Structure

Question 1

Properties of proteins?

Answer 1

They are shorter, rigid and non-rotational C-N bond in the trans group arrangement
Partial negative charge on the O atom and positive charge on the N atom
peptides form H-bonds with other polar groups in polypeptide chains

Question 2

The structures of amino acids?

Answer 2

Primary structure - sequence of amino acids in the peptide chain
Secondary structure - folding or coiling of chain into a shape
Tertiary structure - peptide chain folds on itself and more bonds form
Quaternary structure - folded peptide chains join together forming a whole functional 3D protein

Question 3

Alpha Helix?

Answer 3

H bonds form between O and H of NH every 4th peptide forming an regular right hand helix
3-6 residues which are turn stabilised
R-groups on the outside

Question 4

Beta Pleated Sheets?

Answer 4

Linear peptide chains
H-bonding between peptide chains creating strength
Side chains alternatively lie above and below the plane of the sheet

Question 5

What is supersecondary structure?

Answer 5

Combination of A-helix and B-sheets forming common domains

Question 6

Covalent and Non-covalent forces that stabilise proteins?

Answer 6

Covalent = disulphide bridges
Non-covalent = H-bonds, electrostatic interactions, Van der Waals forces and hydrophobic effects

Question 7

What are Proteins sensitive to?

Answer 7

pH, Temperature and Ionic strength