BIS 105-3

Page 1 of 8 Name KEY Last, First Your Student ID number: Biological Sciences 105 Second Midterm, May 21, 2008 Instructions: Write your answers in the space provided below each question. If you need more space, use the back of the page. For calculation problems, a clear line of calculations must be shown to obtain full credit. Question Value Score Question Value Score 1 4 7 10 2 4 8 12 3 8 9 6 4 20 10 8 5 4 11 10 6 10 12 4 Total 100 Student Authorization I authorize the University to distribute publicly this graded exam (e.g., handed out in class or left in a bin for me to pick up). Signature , Date https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com

Page 2 of 8 1. (4 pts.) Below are listed some of the equations we may have or have not used this quarter. Please match the equation with the statements by placing a letter on the line corresponding to the appropriate equation. A. ¸ ¹ · ¨ © § ± RT E h T k a exp k B. ¸ ¸ ¹ · ¨ ¨ © § ² ² I M K I K S S V v ] [ 1 ] [ ] [ max 0 C. M K S S V v ² ] [ ] [ max 0 D. ³ ´ M I K S S K I V v ² x ¸ ¸ ¹ · ¨ ¨ © § ² ] [ ] [ ] [ 1 max 0 E. E = m c 2 F. eq K RT G ln ' 0 ± ' G. ³ ´ kt e S t P ± ± 1 ) ( 0 H. ¸ ¸ ¹ · ¨ ¨ © § ² ² x ¸ ¸ ¹ · ¨ ¨ © § ² I M I K I K S S K I V v ] [ 1 ] [ ] [ ] [ 1 max 0 I. ] tan [ ] [ ln ' 0 ts reac products RT G G ² ' ' A. This equation describes the accumulation of a product as a function of time in a first order reaction. ___G_____ B. This equation describes competitive inhibition. __B______ C. This is the Michaelis-Menten equation. ___C_______ D. This equation describes uncompetitive inhibition. __H______ E. This equation describes the relationship between a first order rate constant and energy of activation. ___A_____ F. This equation shows the relationship between ' G 0 ’ and the equilibrium constant of the reaction. ___F_____ G. This equation describes noncompetitive inhibition. ___D_____ H. This equation is not often needed in biochemistry. ___E______ I. This equation shows the change in Gibbs Free Energy derived from a reaction starting with non-standard conditions. ___I______ And if you need them, use T = 298 K and R = 8.314 J/mol K https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com

Page 4 of 8 4. (20 pts.) The table below shows data collected for an enzyme reaction that was run with and without an inhibitor, I, at 14 mM. Using the empty spaces in the table and the graph paper on the next page, determine V max , K M , V max,app , and K M,app . What kind of inhibitor is I? What is the value of K I ? x You must report the units on these parameters for full credit. x You must show your work to receive full credit. K M = 5 mM K M,app = 12 mM V max = 150 P mol/s V max,app = 150 P mol/s The type of inhibition observed = competitive K I = 10 mM x Here's a tip: Place the zero point on the abscissa (X-axis) at the middle of the page. Place the zero point on the ordinate 3/4s of the way toward the bottom of the page. On the abscissa let 4 tics = 0.1 and plot between -0.3 and 0.3. On the ordinate let each tic = 0.01 and plot up to 0.03. x Here's another: Do you need to plot all these points? x one more. If you read the line axis intercepts, tell me what they are. v 0 -I v 0 +I [S] (mM) ( P mol/s) ( P mol/s) 0 0 0 4 66 38 8 90 57 12 106 78 16 115 83 20 116 100 24 130 100 28 120 110 32 135 105 https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com

Page 5 of 8 https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com

Page 7 of 8 8. (12 pts.) Answer the following questions about the mechanism of action of acetylcholine esterase. What three amino acids comprise the triad? S,H,D The two products of the breakdown of acetylcholine are _ choline __________ and _ acetic acid _ _ . Of these, which comes off first? Choline Why is it said that acetylcholine esterase operates by a charge relay mechanism? That is, what charge is relayed and where? The charge of the proton is relayed from the H toward the D, and is withdrawn from the S by the protonatable nitrogen on the H. This enzyme is inhibited under mildly acidic conditions. Why? The H must be deprotonated to withdraw the proton from the S. This happens above the pKa for the His R group, which is 6.0. So under mildly acidic conditions, say below pH = 6, the H is >50% protonated and inactive in the mechanism. 9. (6 pts) In lecture K M was described three times, as a ratio of rate constants, as the affinity of the enzyme for the substrate and as the substrate concentration giving v o = ½ V max . Starting with the Michaelis-Menten equation, show that this latter identity is true. That is, prove that K M is the substrate concentration (call it [S] 1/2 ) at which v o = ½ V max . Start with Michaelis-Menten equation, M max 0 K [S] [S] V v ² M 2 1 2 1 max max K [S] [S] V V 2 1 ² M 2 1 2 1 K [S] 2[S] 1 ² 2 1 M 2 1 2[S] K [S] ² 2 1 M [S] K https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com

Page 8 of 8 10. (8 pts) The formation of citrate from _ oxaloacetate __ and __ acetyl-CoA ____ by the enzyme __ citrate synthase ________ is generally thought of as the start of the TCA cycle. In subsequent steps CO 2 is liberated during the conversion of __ isocitrate ____ to D -ketoglutarate _ by the enzyme _ isocitrate dehydrogenase _, and another CO 2 is liberated during the conversion of _ D -ketoglutarate _ to _ succinyl-CoA __ by the enzyme ___ D -ketoglutarate dehydrogenase ______. These enzymes are so-named to reflect their ability to __ reduce ________ the co-factor __ NAD + __________ to __ NADH + H + _____. 11. (10 pts) If the free energy released by the uncontrolled compete oxidation of glucose is 2,840 kJ/mol, how efficient is the energy capture when glucose is metabolized anaerobically? How is that different when glucose is metabolized aerobically? Calculate the relative efficiencies. Give a complete justification for your answer to receive full credit. In glycolysis, 2 ATP are made. Since the ' G o ’ for ATP synthesis is 30.5 kJ , the efficiency is calculated as % 1 . 2 2840 5 . 30 2 100 u u In respiration, 38 ATP are made, At 30.5 kJ/mol, the efficiency is % 1 . 40 2840 5 . 30 38 100 u u 12. (4 pts.) From our point of view, anaerobic glucose metabolism in yeast leads to some 13,000 traffic fatalities in the US per year. From the yeast’s point of view, why do they do it? That is, what is the point of converting the end product of glycolysis into ethanol? The production of ethanol from pyruvate serves to regenerate NAD + from NADH + H + , which is needed for glycolysis. https://www.coursehero.com/file/8031844/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com Powered by TCPDF (www.tcpdf.org) https://www.coursehero.com/file/13087693/BIS105SpringQtr2008ThegMT2KEY/ This study resource was shared via CourseHero.com Powered by TCPDF (www.tcpdf.org)