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Unformatted text preview: name ________________________________________ BICH 441 EXAM 3 April 24, 2007 An Aggie does not lie, cheat, or steal, or tolerate those who do. I swear on my honor as an Aggie that I have not received or given unauthorized aid on this exam, and I am not aware of others who have received or given unauthorized aid on this exam. signed _________________________________________________________ NO CALCULATORS! Before you begin, write your name on each page (there are 5 pages) and sign the Aggie Honor Code statement above. Questions 1-15 (2 pts each). Enter your answer on your Scantron sheet. 1. The reaction shown below: A. B. C. D. is part of the pathway for synthesis of ketone bodies from acetyl-CoA. requires Coenzyme B12. is part of the pathway for oxidation of unsaturated fatty acids. is catalyzed by methylmalonyl-CoA epimerase. 2. Formation of the molecule shown: A. is rate-determining in the β-oxidation of fatty acids. B. is catalyzed by HMG-CoA lyase. C. occurs in the mitochondrial matrix. D. all of the above 3. In adipose cells: A. triacylglycerol is packaged into chylomicrons. B. insulin inhibits synthesis of fatty acids. C. glucagon activates triacylglycerol lipase. D. all of the above 4. Which of the following is false? A. Bile salts help solubilize dietary fat. B. Serum albumin is a carrier protein for fatty acids derived from dietary triacylglycerol. C. Bile salts are structurally similar to cholesterol. D. Chylomicrons are degraded by lipoprotein lipase. 5. The amino acid proline is one of the 20 amino acids required for synthesis of proteins. Proline can be synthesized in human cells from glutamate, and it is catabolized in liver to α-ketoglutarate. Thus, proline is: A.. essential and ketogenic. B. essential and glucogenic. C. nonessential and ketogenic. D. nonessential and glucogenic. 6. The molecule shown: A. is an intermediate in the reaction catalyzed by acyl-CoA synthetase. B. is a fatty acyl-CoA. C. is an intermediate in the reaction catalyzed by acetyl-CoA carboxylase. D. must cross the inner mitochondrial membrane before β-oxidation can occur. name ______________________________________ 7. The reaction that converts the molecule shown to pyruvate: A. is catalyzed by malate dehydrogenase. B. is located in the mitochondrial matrix. C. generates reducing power for fatty acid synthesis. D. all of the above 8. The activity of the fatty acid synthase multienzyme complex that generates the molecule shown is: A. enoyl-ACP reductase. B. acetyl transferase. C. β-hydroxyacyl-ACP dehydratase. D. β-ketoacyl-ACP reductase. 9. Which of the following activities of the fatty acid synthase multienzyme complex is used only one time in the synthesis of a fatty acid that contains 16 carbon atoms? A. β-ketoacyl-ACP synthase B. acetyl transferase C. β-hydroxyacyl-ACP dehydratase D. β-ketoacyl-ACP reductase 10. The enzyme _____________________ is rate-determining in fatty acid synthesis in mammals, and its activity is _______________ by ___________________. A. B. C. D. β-ketoacyl-ACP synthase; increased; citrate carnitine acyltransferase I; decreased; malonyl-CoA acetyl-CoA carboxylase; increased; glucagon acetyl-CoA carboxylase; increased; citrate 11. In the synthesis of unsaturated fatty acids by stearoyl-CoA desaturase, the final electron acceptor is: A. O2 B. NAD+ C. NADP+ D. FAD 12. Acetyl-CoA labeled with 14C in the number 1 carbon (the carboxylic acid carbon of acetate) is used in fatty acid synthesis catalyzed by acetyl-CoA carboxylase and fatty acid synthase. After synthesis of a fatty acid containing 16 carbon atoms, which carbons in the fatty acid will contain label? A. only carbon number 16 (the carbon farthest from the carboxylic acid) B. only carbon number 15 C. all the even-numbered carbons D. all the odd-numbered carbons 13. Nitrogen fixation catalyzed by the nitrogenase complex requires ______ moles of electrons and ________ moles of ATP for each mole of N2 that is converted to NH4+. A. 8 ; 1 6 B. 4; 8 C. 4; 16 D. 8 ; 8 14. Triacylglycerol made in liver and sent out to other tissues for storage or β-oxidation is packaged in the form of: A. chylomicrons. B. HDL. C. VLDL. D. L DL . 15. Cells that have sufficient cholesterol limit their uptake of additional cholesterol by: A. activating lipoprotein lipase. B. inhibiting the synthesis of LDL receptor protein. C. exporting cholesterol in the form of HDL. D. all of the above 2 name ______________________________________ ****************************************************************************************** PLEASE READ THIS. In some of the following questions, you are asked to draw structures of reactants and products. Unless specifically stated otherwise, you do not need to draw the structures of CoA, ATP, ADP, NAD(P)+, or NAD(P)H. You should, however, show when each is needed in the appropriate reactions. Also, unless specifically stated, you do not need to write reaction mechanisms. ****************************************************************************************** Questions 16-21. Write your answers in the space provided. 16 (15 pts). Starting with the molecule shown, draw the steps in β-oxidation until you generate acetyl-CoA as one of the products. Except as noted in the “Please Read This” section above, show the names and structures of all reactants and products, and name the enzymes. 17 (15 pts). Acetyl-CoA is generated from pyruvate in the mitochondrial matrix via the action of the pyruvate dehydrogenase complex. Synthesis of fatty acids from acetyl-CoA and malonyl-CoA occurs in the cytosol. Show the sequence of reactions by which acetyl-CoA in the mitochondrial matrix is converted to acetyl-CoA and malonyl-CoA in the cytosol. Except as noted in the “Please Read This” section above, show the names and structures of all reactants and products, and name the enzymes. Specifically indicate what molecule(s) cross the inner mitochondrial membrane. 3 name ______________________________________ 18 (10 pts). Draw the mechanism of the reaction catalyzed by HMG-CoA reductase. You do not need to draw the structure of CoA, and you can abbreviate the structure of NADP(H) by drawing only the nicotinamide ring. 19. (15 pts). Starting with carbamoyl-phosphate and ornithine, draw the reactions of the urea cycle. Except as noted in the “Please Read This” section on page 3, show the names and structures of all reactants and products, and name the enzymes. Specifically indicate what molecule(s) cross the inner mitochondrial membrane. 4 name ______________________________________ 20 (10 pts). The molecule shown is a Schiff base between pyridoxal phosphate and the amino acid alanine. Beginning with this structure, draw the reaction mechanism of the transaminase-catalyzed formation of pyruvate. Show the steps in the mechanism up to the formation of the pyridoxamine form of the coenzyme and the release of pyruvate. A. 21 (5 pts). Write the names of the molecules shown in the space provided. A. _______________________________________ B. _______________________________________ C. _______________________________________ D. _______________________________________ E. _______________________________________ B. C. D. E. 5 ...
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This note was uploaded on 03/27/2010 for the course BICH 441 taught by Professor Staff during the Spring '08 term at Texas A&M.

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