Exam-style question - PHAR2811 Enzyme Kinetics Q1. Which one of the following statements is INCORRECT? A. Enzymes are biocatalysts B. Enzymes slow down biochemical reactions C. Enzymes are not modified in biochemical reactions D. Enzymes are potential drug targets Q2. Which of the following statements is INCORRECT? A. Temperature should always be very high to increase the enzymatic reaction rate B. pH influences the conformation of enzymes C. Cofactors are required for enzyme activity occasionally D. Inhibitors can influence the enzymatic reaction rate Q3. Which of the following statement is CORRECT? A. Competitive, non-competitive and uncompetitive inhibitors are non-reversible inhibitors B. Competitive inhibitors are most likely to bind to the active site of an enzyme C. Non-competitive inhibitors are most likely to bind to the active site of an enzyme D. Uncompetitive inhibitors are most likely to bind to the active site of an enzyme Q4. The y-intercept of the Lineweaver-Burk plot Vmax Km 1 + 1 ) corresponds with which [S] Vmax of the following terms? A. 1 V B. Km Vmax
1 C. [S] 1 D. Vmax Q5. The gradient of the Lineweaver-Burk plot (- = 1 Km 1 1 + Vmax [S] corresponds with which of Vmax' the following terms? 1 A. V Km B. Vmax C. 1 1 [S] 1 D. Vmax SAQ. The figure shows Lineweaver-Burk plots in the presence or absence of an inhibitor. 1 = V K m V MAX 1 + [S] 1 V MAX No inhibitor 1 = V K m V MAX 1 ( + [S] [ I ] -) + K i 1 ( 1 + K ) [ I ] V MAX i With inhibitor 300 y = 97.81x + 51.211 R^2=0.9995 (with inhibitor) 250 1 200 With inhibitor 1/V (1/(uM / min)) 150 No inhibitor 100 50 0 -1 0 y = 40.12x+ 19.513 R^2 = 0.9995 (no inhibitor) 1 2 3 1/[s] (uM-1)
a) Calculate Vmax from the graph and the equations above. Show your working and unit Answer: Vmax = 0.0512 pM/min b) Calculate Km from the equation shown in the figure above. Show your working and units Answer: Km = 2.0541 pM c) If the enzyme concentration is 1 nM, what is Kcat? Show your working and units. Answer: Kcat = 51.2 min-1