Questions on Proteins & enzymes

1. Three 2-amino acids are aspartic acid, glutamic acid and threonine.
Their structures are given in Section 33 of the IB chemistry data booklet.

(a) Draw the structure of one trimer containing the residues of each of the three 2-amino acids after they have undergone condensation reactions.

(b) State how many other different trimers can be made by condensing the three acids together?

2. Explain the difference between the secondary and tertiary structures of proteins.

3. The diagram below shows two adjacent strands of a protein.

Identify the type of interaction that is occurring between:

(i) tryptophan (Trp) and leucine (Leu)

(ii) glutamic acid (Glu) and arginine (Arg)

(iii) tyrosine (Tyr) and histidine (His)

(iv) cysteine (Cys) and cysteine (Cys)

(v) glutamic acid (Glu) and lysine (Lys)

4. Describe how you could analyse a protein to determine which 2-amino acids it contains using paper chromatography.

5. (a) The isoelectric point of alanine is at pH 6.0. State the structural formula of alanine in a
solution with the following pH values:

(i) pH = 3.0
(ii) pH = 6.0
(iii) pH = 9.0

(b) Outline how three different amino acids, A, B and C with isoelectric points of 5.1, 6.3 and
7.6 respectively could be separated using PAGE (polyacrylamide gel electrophoresis).

6. Explain why changing the pH can have a large effect on the ability of an enzyme to catalyse a reaction.

7. Explain why increasing the temperature increases the rate of an enzyme-catalysed reaction but only up to a certain temperature.

Download the  Protein & enzyme question  to give to your students.