Page 1 of 9 Student No .: Course: BCHM QUEEN'S UNIVERSITY EXAMINATIONS - 3 OCTOBER 2018 Faculty of Arts & Science Biochemistry 310 and 315 Dr. Robert Campbell and Dr. Steven Smith INSTRUCTIONS 1. Enter your student number and course section in the appropriate places on this Exam Paper. 2. There are 9 Short-Answer questions. Please complete the Short-Answer questions in the space provided in the exam. 3. HAND IN THIS EXAM PAPER 4. The exam duration is 90 minutes. Q1 Q2 Q3 Q4 Q5 Total /33 /3 /5 /11 /4 /10
The following table of pK values may be useful: Amino acid pK? (-COOH) Alanine 2.3 Arginine 2.2 Asparagine 2.0 Aspartate 1.9 Cysteine 2.0 Glutamine 2.2 Glutamate 2.2 Glycine 2.3 Histidine 1.8 Isoleucine 2.4 Leucine 2.4 Lysine 2.2 Methionine Phenylalanine Proline 2.0 Serine Threonine Tryptophan Tyrosine Valine 2.3 1.8 2.2 2.1 2.4 2.2 2.3 Page 2 of 9 pK2 (-NH3+) 9.7 9.0 8.8 9.6 10.3 9.1 9.7 9.6 9.2 9.7 9.6 9.0 9.2 9.1 11.0 9.1 9.6 9.4 9.1 9.6 pKR (R group) 12.5 3.6 8.2 4.2 6.0 10.5 10.0
Page 3 of 9 1. When a molecule with hydrophobic regions is dissolved in water, there is a tendency for those hydrophobic regions to stick together. Explain why it is the behaviour of the water molecules rather than the interactions of the hydrophobic molecules that makes this process energetically favourable (3 marks). 2. (total 5 marks) You are embarking on the purification of an enzyme called robstevase that you have obtained from a human brain cell extract. a) As a first step you check for the solubility of the enzyme in different concentrations of (NH4)2SO4. You assay all of the precipitate and supernatant fractions for the total amount of protein and the number of enzyme units of robstevase. The results are shown below: [(NH4)2SO4] (% saturation) Sample initial extract 20% Precipitate #1 20% Supernatant #1 3400 30% Precipitate #2 30% Supernatant #2 60% Precipitate #3 60% Supernatant #3 100 Total protein (mg) 4000 # units (umol/min) Specific activity (units/mg) 1000 500 1 990 1000 2 2000 900 1500 850 5 Fill in the missing specific activity values. (2 marks)