DNA and Co

Question 1

What is the isoelectric point?

Answer 1

The pH at which the amino acid has no net charge

Question 2

What is the effect of pH on amino acid structure?

Answer 2

1) At a pH which is lower than the isoelectric point the amino acid acts as a base and accepts hydrogen ions
2) At a pH which is lower than the isoelectric point the amino acid acts as a acid and donates hydrogen ions

Question 3

Why do amino acids have high melting points?

Answer 3

Zwitterions form ionic bonds with each other

Question 4

What are the key definitions of the primary to tertiary structure of proteins?

Answer 4

1) Sequence of aa in a protein chain held together by peptide bonds
2) A 3D structure formed by the primary structure such as a alpha-helix or beta pleated sheets held together by peptide and hydrogen bonds
3) The 3D arrangement of a single polypeptide chain held together by VDWs forces between non-polar aa, hydrogen bonds between amine and carboxylic acids groups, ionic bonds between aa side chains containing charged groups and disulphide bonds.

Question 5

What is a disulphide bond?

Answer 5

A covalent bond between two cysteine residues