FA06Exam2Key - Name (print): Network ID: Signature: Student...

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Unformatted text preview: Name (print): Network ID: Signature: Student ID #: MCB 450 EXAM II 2 November 2006 Dr. Mintel Print your name, sign your name, previde your network ID and student ID number at the top of this page and your name at the top of every other page. This exam comists of 9 pages and is a total of 100 points. Your exam booklet will be collected at the conclusion of the examination period. Your grade will be based on the written work contained within the spaces provided. Illegible work will not be considered. You are permitted to use a calculator. No notes of ANY kind are allowed. It is your responsibility to avoid the appearance of cheating and to uphold the integrity of the examination system. DO NOT OPEN THE EXAM BOOKLET UNTIL INSTRUCTED TO DO SO. BEST OF LUCK ON THE EXAM. _— —m- —“ Multi le-Choice 3 oints each 60 oints total For each of the following questions, encircle the letter corresponding to the BEST response. 1. Which of the following is NOT an assumption made in the derivation of the ichaselis—Menten equation? The reaction proceeds with a large, negative change in free energy. 'n' The rate of formation of ES is balanced by the rate of its destruction, eithertoE+ SortoP+E. C. The k-2 step can be ignored. D. Only one substrate is considered. B. (All of the above are assumptions usually made). 2. Which of the following correctly defines KM? A. It is equal to the quantity klf(k-l + k2) B. It is the dissociation constant for the enzyme-substrate complex. C. It is equal to mefl. @ It is the substrate concentration giving half-maximal velocity. It is equal to the quantity k-1.*’(kl + kg) 3. Diisopropylfluorophosphate (DIFP) inactivates trypsin, chymotrypsin, acetylcholinesterase, and many other enzymes. What best explains the basis for this effect? A. It serves as a noncompetitive inhibitor of those enzymes. ® It forms a covalent bond with the —OH group of Ser. C. It binds to the active site of those enzymes, preventing binding of substrate. D. E. It binds to the Asp residue in the catalytic triad. It interferes with proton exchange by the sidechain of Lys. 4. Which statement about a hemoglobin molecule is INCORRECT? A. There are four polypeptide chains non-covalently associated. Each polypeptide chain is associated with one porphyrin ring. @ There is a total of four Fe3+ atoms in oxyhemoglobin. One BPG can bind in a central cavity. E. HbA2 contains or. and 5 chains. 9. Which of the following statements about the X-ray structure of myoglobin is INCORRECT? A B.- C. D. (9 There are eight regions of or helix. The regions between the helices frequently contain Pro or [3 turns. There is one porphyrin ring per molecule. One molecule of oxygen can be bound to the Fe2+ of the porphyrin ring. Hydrophilic amino acid residues are buried in the interior. Which of the following is an INCORRECT statement about NAD+ and FAD? A. B. C. £9 E. NAD+ transfers one hydrogen as a hydride ion and the other as a proton, whereas FAD accepts two hydrogens as free radicals. They are both derived from water-soluble vitamins. FAD is generally a stronger oxidant than is NAD+ NAD+ contains the isoalloxazine ring system whereas FAD does not. Reoxidation of the reduced form of NAD+ yields more ATP than reoxidation of the reduced form of FAD. Which of the following is an allosteric enzyme of glycolysis? A. C? triose phosphate isomerase enolase aldolase puruvate kinase glyceraldehyde 3-phosphate dehydrogenase At higher concentrations of fructose 2-6 bisphosphate, the rate of the fructose 1,6- bisphosphate phosphatase rcactiou would be expected to be A. (E) greater than equal, or approximately equal to, less than the rate at lower concentrations of fructose 2-6 bisphosphate. A lipoprotein with a higher ratio of lipid to protein would be expected to have a density A. B. @ greater than equal, or approximately equal to, less than a lip0protein with a lower ratio of protein to lipid. 10. Which of the following INCORRECTLY pairs a coenzymc with its function in the pyruvate dehydrogenase reaction? @ TPP : formation of thioesters . Lipoic acid : acyl transfer C. Lipoic acid : oxidation D. NAD+ : oxidation E. FAD : oxidation 1 1. A derivative of which water-soluble vitamin is NOT required for the conversion of a-ketoglutarate to succinyl CoA in the TCA cycle? A. thiamin B. riboflavin C. niacin pyridoxine a pantothenic acid 12. Per turn of the tricarboxylic acid cycle, how many MAD+ are produced? 0 B. 1 C. 2 D. 3 E. 4 13. Per turn of the tricarboxylic acid cycle, how many FAD are produced? 0 @ 1 C. 2 D. 3 E. 4 14. How many protons are transported out of the mitochondrion when an electron pair passes from an NAD-linked substrate to oxygen? A. 2 B. 4 C. 6 8 10 15. The following reactions are involved in the catabolism of galactose in the liver: galactose + ATP = galactose 1-phosphate + ADP galactose 1-phosphate + UDP-glucose = UDP-galactose + glucose 1-phosphate UDP-galactose = UDP-glucose glucose 1-phosphatc = glucose 6-phosphate When galactose is combusted to carbon dioxide and water in a typical liver cell. what is the NET yield of ATP? Assume the glycemphosphate shuttle is operating. A. 24 B. 26 C. 28 @D 30 E. 32 16. When pyruvate is combusted to carbon dioxide and water in a typical liver cell, what is the NET yield of ATP? A. 12 B. 14 a w . 18 E. 19 1?. When 14C02 is added to a suspension of Chiareila, the first stable labeled compound that can be isolated is A. ribulose 1,5 bisphosphate glyceraldehyde 3-phosphate é 3-phosphog1ycerate D. xylulose 5-phosphate E. ribose 5-phohphate 18. Which of the following enzymes is NOT involved in the conversion of glycogen to glucose in a liver cell? A debranching enzyme phosphorylase glucose 6-phosphatase B. C. (1-1 ,6 glucosidase & phosphoglucoisomerase 19. Which of the following CORRECTLY pairs a compound with its effects on electron transport and oxidative phosphorylation? Cyanide : Inhibitor of cyt c oxidase Carbon monoxide : Inhibitor of succinate dehydrogenase Oligomycin : uncoupling agent 2,4 dinitrophenol : inhibitor of ATP synthase 20. Which of the following would be the expected result when dinitrOphenol is added to isolated mitochondria? C. D. E. Electron transport would occur, but oxidative phosphorylation would not. Neither electron transport nor oxidative phosphorylation would occur. Electron transport and oxidative phosphorylation would occur, but only from FAD-linked substrates. Electron transport and oxidative phOSphorylation would occur, but only from NAD—linked substrates. Electron transport and oxidative phosphorylation would occur from both FAD-linked and NAD-linked substrates. Short Answer (Credit for each item is given in parentheses; 21. (4) (a) (13) Under conditions of vigorous exercise, voluntary skeletal muscle derives its energy from the anaerobic conversion of glucosyl units of glycogen to lactate. lactate, rather than pyruv-jtegt/he progrfi b + m r' mm A net of how many ATP is produced as a glucosyl unit of glycogen is converted to lactate? 5 22. 24. (6) Give the function of each of the following in the light reactions of photosynthesis. (a) photosystem I a AMI—DH; (b) photosystem 11 a4: (0) the electron transport chain joining the two ph tosysflr Ws/mfes if?" twwe (4) When pyruvate labeled with MC in its methyl group is added to a liver cell preparatiori, glucose labeled in positions 1,2, 5, and 6 can be sub e ' uently_ isolated. Propose an explanation fortlis 0b Nation. at I 4,9, 2.: e t fir a” x “9 Law game/192719 wrflb @mfi we/ 23 (4) Write a balanced equation (using words) for the conversion of pyruvgj I? glucose in a typical liver cc 1. + 2 "J‘ 2 f ffigfir+ m> 25. % Sat 26. (8) Below are shown two oxygen-dissociation curves for hemoglobin. Decide which curve is appropriate for each of the following descriptors. p02 2. a) the curve at the higher concentration of BPG b) the curve at the higher pH 1 l c) the curve at the lower pCOz d) Assuming one Curve correSponds to HbA and the other to HbF, which is the I one for HbF‘? (2) Give the two major products of the pentose phosphate pathway. 27. (12) Data on the effects of an enzyme inhibitor are given in the following table. Substrate Concentration m . V(mmotr ml" min' ) 0.5 L With . . 1/ 1-" n3 Inhibitor \ ._l_._.l._1_l_._ 2 3'4 5 1/5 (3) Graph the data using a double-reciprocal plot. Label the line for the inhibited case. ‘\ p2. M‘a/ (b) Classify the inhibition according to type. M” M #2 7L 6 (c) Provide a possible hysical basis for the i tibition W # b! ‘ :9 f a % 9 )fl i z 451 I :5”! 7‘6) $0105 777? 7‘6 j ((1) Give a kinetic mechanism for this gm of inhibiwg Ewe-vase (e) Can the in ibition by increasing substrate concentration? Answer "yes" or "no-l! 0 (f) Calculate a value for KM, giving the appropriate units. X MT: Hymn = 125 :0.4‘IVZM The End ...
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This note was uploaded on 09/14/2009 for the course MCB 450 taught by Professor Mintel during the Summer '07 term at University of Illinois at Urbana–Champaign.

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FA06Exam2Key - Name (print): Network ID: Signature: Student...

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