Faculty of Science, IUG

Faculty of Science, IUG Dept. of Chemistry and Biochemistry Mid-Term Exam. Enzymes kinetics(Bioc4307)

Date: 22/11/2006 Name:------, NO.------Answer the following: I-Account for the following (10 pts). A)Pepsin is not used in AA sequencing. B)Some enzymes are found in multi-enzyme complex. C)Lactose synthase does not act during pregnancy. D)Induced fit mechanism is more acceptable than lock and key mechanism. E)Catalytic power of enzymes depend on the environment in which they are present.

II- Starting from M.M. equation, prove that [p] = Vmax. t showing plots of V, [S] and [P] vs. t. (6pts). III- Rearrange the M.M. equation to give Vo as a function of Vo/[s] and plot it (3 pts). A) What is the slope, Y-intercept, and X- intercept (3 pts). B) Sketch the plot in presence of CI and NCI(4pts). IV- Given the following data: [S]µM Vo µM/min.(-I) Vo µM/min.(+I) 3 10.4 4.1 5 14.5 6.1 10 22.5 11.3 30 33.8 22.6 90 40.5 33.8

.(A) Draw L.B. plot (4pts B) Determine Vmax (± I) , Km (± I),type of .(inhibition, and Ki if [I] is 2mM (8pts c)At [S] = 10 µM, and [I] = 2mM, What fraction of the enzyme molecules have a bound substrate and a bound inhibitor? (2pts) Faculty of Science, IUG Dept. of Chemistry and Biochemistry Midterm Exam. Chemistry of proteins and lipids(Bioc4308) Midterm Exam Date:2/12 /2005 Name------& NO.------Answer the following I- Sketch the titration curve, calculate pI and determine the regions of the buffer capacity of ASP. The pK values of its Alfa COOH, Alfa amino , and Beta COOH groups are 2.1, 9.2, and 3.9 respectively. (6pts).

II-Compare and contrast 1-Fatty acid oxidation and synthesis with respect of site of the process, acyl carrier, reductant and oxidant, the net equation, sequential units added, organization of the enzyme systems (6pts). 2- Lowery method and Biuret methods with respect of composition, reaction with a protein, sensitivity, the wave length of absorbance (4pts).

III-Discuss by showing structure of the following biochemical processes(15pts). 1-Keto-genesis. 2-Synthesis of TAG starting from glycerol. 3-Transfer of acetylCoA from mitochondria to cytoplasm by malate-oxaloacetate shuttle. Faculty of Science, IUG Dept. of Chemistry and Biochemistry Incomplete Exam. Chemistry of proteins and lipids(Bioc4308) Date: March/2006 Name------& NO.------Answer the following

I)-Write structural formulas of the following biochemical processes. 1-Ketolgenesis. 2-Formation of Cyst. From Met. 3-Formation of Gly from Glyceraldehyde 3- p. 4- Formation of TAG from glycerol in a small intestinal cell.

II)-Write the following biochemical processes (without Structural formulas). 1-Fate of heme in the body. 2-Formation of linoleic acid (18:Dalta9,12) from oliec acid(18:dalta9)in the body.

III)- Sketch the approximate titration curve for: 1- Glutamic acid. 2- Lysine. Faculty of Science, IUG Dept. of Chemistry and Biochemistry Final Exam. Enzymes kinetics(Bioc4307) Date: 11/1/2006 Name:------, NO.------Answer the following: / I- Starting from M.M. equation, derive Ln [S]0/[S] = K t and show plots of V, [S] and [P] vs. t. (10pts). II- Rearrange the M.M. equation to give [s]o/Vo as a function of [s]o and plot it (4 pts). 1-What is the slope, Y-intercept, and X-intercept (3 pts). 2-Sketch the plot in presence of CI, NCI, and UNCI (3 pts). III- Given the following data: [S]µM Vo µM/min.(-I) Vo µM/min.(+I) 3 10.4 2.1 5 14.5 2.9 10 22.5 4.5 30 33.8 6.8 90 40.5 8.1 .(Draw L.B. plot (4pts -1 .(Determine Vmax (± I) , Km (± I),type of inhibition, and Ki if [I] is 100 µM (8pts -2 3- If [s] = 30 µM, what fraction of the enzyme molecules have a bound substrate (± I)?(4 pts) IV- If a pure enzyme has a specific activity of 200 U/mg enzyme(6 pts). a)Calculate the Kcat if M.W. of the enzyme is 200,000 Dalton (explain the answer). b)Calculate the time required for one catalytic cycle(explain the answer). V-(a) What concentration of competitive inhibitor is required to yield 25% activation at a substrate concentration of 1.5x10-3 M if Km = 2.9x10-4 M and Ki = 2x10-5 M?(5 pts). (b) Calculate concentration of the substrate that must be increased to reestablish the velocity at the original uninhibited value?(2pts). VI- For 120 µM/min units of a pure enzyme preparation (10 mg/ml,360000 Dalton). Calculate: kp,1/Kp and S.A(7 pts). VII)Complete the following enzyme purification scheme (12 pts). Total Volume Conc Enzyme Step units S.A % Yield PF (ml) (mg/ml) (U/ml) Crude cell free 1000 10 40 extract Ammonium sulfate 250 20 100 Heat denaturation 100 40 200