Coenzyme A is a substrate or a product. (four enzymes) NADH is a substrate or a product. (five enzymes)

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1 BCH 4053 August 4, 2000 Mini-Exam NAME (25) 1. Following is an alphabetical list of the glycolytic and TCA cycle enzymes plus a few other enzymes we have discussed. Choose enzymes from this list that are described by the statements below, and place the number or numbers of the enzyme in the blank to the left of the statement. In most cases, more than one enzyme will apply. Given in parenthesis after the statement is the target number of enzymes for you to identify. Page Points Total (1) aconitase (2) aldolase (3) citrate synthase (4) enolase (5) fumarase (6) glucose-6-phosphate isomerase (phosphoglucoisomerase) (7) glyceraldehyde -3-phosphate dehydrogenase (8) hexokinase (9) isocitrate dehydrogenase (10) á-ketoglutarate dehydrogenase complex (11) malate dehydrogenase (12) malic enzyme (13) phosphoenolpyruvate carboxykinase (14) phosphofructokinase (15) phosphoglycerate mutase (16) phosphoglycerate kinase (17) pyruvate carboxylase (18) pyruvate dehydrogenase complex (19) pyruvate kinase (20) succinate dehydrogenase (21) succinyl-coa synthetase (22) triose phosphate isomerase (a) (b) (c) (d) (e) (f) CO 2 is a substrate or a product. (six enzymes) ATP is a substrate or a product. (five enzymes) Coenzyme A is a substrate or a product. (four enzymes) NADH is a substrate or a product. (five enzymes) Thiamine pyrophosphate is a prosthetic group. (two enzymes) Possible anaplerotic reactions. (three enzymes)

2 BCH 4053 Mini-Exam Page 2 Name Answer question 2 or 3: (20) Points 2. Starting with [2-14 C]-glucose, trace the radioactive carbon through glycolysis and the first turn of the citric acid cycle, showing how oxaloacetate would be labeled at the end of the first turn. To do so, give the structure of each intermediate in the pathway, and circle the carbon atom(s) of each intermediate which derive from carbon-2 of glucose. 3. One of the proton dissociations of hemoglobin occurs near neutral ph. This dissociation is affected by the binding of oxygen to Hb. Assume that the dissociations for oxyhemoglobin (HbO 2 ) and deoxyhemoglobin (Hb) can be treated as simple monoprotic acids as follows: HHbO 2 H + + HbO 2, pk = 6.6; and HHb H + + Hb, pk = 8.2; (a) (b) Assume that blood is 3.0 mm in hemoglobin. At the plasma ph of 7.4, and the hemoglobin in the lungs fully oxygenated, what are the concentrations of the protonated (HHbO 2 ) and unprotonated (HbO 2 ) forms? In tissues, the pressure of O 2 drops, and the oxygen dissociates from hemoglobin. The deoxyhemoglobin is a stronger base, and must be titrated with protons for the ph to remain constant at 7.4. Assuming the oxygen were completely dissociated, how many protons would be required per liter to produce the proper Hb/HHb ratio for ph 7.4?

3 BCH 4053 Mini-Exam Page 3 Name Answer question 4 or 5: (20) Points 4. ATP can be synthesized from phosphoenolpyruvate (PEP) in the following reaction: PEP + ADP Pyruvate + ATP (a) Calculate D G o ' and K' for this reaction as written. ( G o ' of hydrolysis for ATP is 30.5 kj/mol and for PEP is 62.2 kj/mol.) R = J/mol-K, and assume T = 37 o C. (b) What PEP/Pyruvate ratio is necessary to maintain an ATP/ADP ratio of 100? (c) Calculate Q' and D G for this reaction if the ATP/ADP ratio were 50 and the pyruvate/pep ratio were 50. (d) What is the difference between D G o and D G o ' for this or any other biochemical reaction? 5. For the peptide glu.lys.phe.his.asp Give the abbreviation for the peptide using the single letter amino acid abbreviations. (a) Calculate the charge on the peptide in strong acid (ph = 1). (b) Calculate the charge on the peptide in strong base (ph = 14). (c) (d) Calculate the pi of the peptide. Would the peptide migrate to the anode (+ electrode) or the cathode (- electrode) at ph 7.0?

4 BCH 4053 Mini-Exam Page 4 Name Answer question 6 or 7 (20) Points 6. Give the step-wise mechanism catalyzed by the enzyme a -ketoglutarate dehydrogenase, showing the partial structure of all the enzyme-bound intermediates. Identify the protein components catalyzing each step and the coenzymes involved as either cosubstrates or prosthetic groups. (Remember this mechanism is like that of pyruvate dehydrogenase). 7. Given the following data for a peptidase hydrolysing the dipeptide gly.gly: S (mm) v (mmol/min) Plot these data in the Lineweaver-Burk plot and determine Vm and Km from the graph. Show your work below, but obtain a piece of graph paper to use for the graphs. Use care in selecting your axes. Be sure to put your name on the paper, and staple it to the test.

5 BCH 4053 Mini-Exam Page 5 Name 8. Draw the structure of 6 of the following: (18 points) (a). Guanosine (b). Arachidonic acid (c). Mannose (Haworth projection) (d). Phosphatidyl choline (e). AT base pair (f). Sucrose (Haworth projection) (g). Stearic acid (h). Cholesterol

Answer three from questions 5, 6, 7, 8, and 9.

Answer three from questions 5, 6, 7, 8, and 9. BCH 4053 May 1, 2003 FINAL EXAM NAME There are 9 pages and 9 questions on the exam. nly five are to be answered, each worth 20 points. Answer two from questions 1, 2, 3, and 4 Answer three from questions