CH395G FINAL (3 rd ) EXAM Kitto/Hackert - Fall 2003

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1 CH395G FINAL (3 rd ) EXAM Kitto/Hackert - Fall A cell in an active, catabolic state has a. a high (ATP/ADP) and a high (NADH/NAD + ) ratio b. a high (ATP/ADP) and a low (NADH/NAD + ) ratio c. a low (ATP/ADP) and a low (NADH/NAD + ) ratio d. a low (ATP/ADP) and a high (NADH/NAD + ) ratio 2. Oxidative Phosphorylation is coupled to electron transport in a. Complexes I, II and III b. Complexes I, III and IV c. Complexes I, II and IV d. Complexes II, III, and IV e. all four respiratory complexes 3. The compound that condenses with CO 2 in the first reaction of carbon dioxide fixation in the dark reactions of photosynthesis is: a. ribose-1,5-bisphosphate. b. ribulose-1,5-bisphosphate. c. ribulose-5-phosphate. d. 3-phosphoglycerate. e. rubisco. 4. Ketone bodies a. are produced in the liver mitochondria through a process called ketogenesis. b. are water-soluble equivalents of glycerol. c. consist of acetoacetate, D-β-hydroxybutyrate and acetone. d. both a and b e. both a and c 5. Acetyl-CoA can be used for all of the following except a. forming oxaloacetate in plants b. forming oxaloacetate in humans c. synthesizing fatty acids d. synthesizing cholesterol e. synthesizing ketone bodies 6. Oxidative reactions of the pentose phosphate pathway a. produce NADPH rather than NADH b. require biotin c. require coenzyme A d. require thiamine pyrophosphate

2 7. The reaction in which malate is oxidized to oxaloacetate is not thermodynamically favored. It takes place because a. it is coupled to ATP hydrolysis b. it involves substrate-level Phosphorylation c. the product is continuously used up in the next reaction of the cycle, which is thermodynamically favored d. it is coupled to a strong reduction 8. Deoxyribonucleotides a. are kept in balance through feedback control to ensure proper intracellular ratios b. are synthesized de novo from deoxyribose-containing precursors c. are formed by the reduction of the C3 position of their corresponding ribonucleotides d. utilizing ribonucleotide reductase, thioredoxin, thioredoxin reductase in the electron-transfer pathway, and the final reducing equivalents are provided by NADH e. both b and d 9. Which of the following coenzymes is not a nucleotide coenzyme? a. NAD + b. FAD c. coenzyme A d. biotin e. FMN 10. Which statement about lipids is not true? a. Most dietary lipids are stored as triacylglycerols, and these are the major form of metabolic energy storage in humans. b. Lipids digested by the intestinal mucosal are packaged as triacylglycerols into chylomicrons, whereas triacylglycerols synthesized by the liver are packaged into high density lipoproteins (HDL). c. Fats yield over twice the energy of an equal mass of dry carbohydrates or proteins. d. Fats are digested at lipid-water interfaces, therefore emulsification of fats by bile salts increases the rate of digestion. e. Triacylglycerols are hydrolyzed to free fatty acids and glycerol, which is converted to a glycolytic intermediate.

3 11. Of the cofactors below, which can be used in the transfer of a methylene (-CH 2 -) group? a. S-adenosylmethionine b. biotin c. tetrahydrofolate d. pyridoxal phosphate e. coenzyme A 12. Which of the following statements about the glyoxylate cycle is false? a. Only plants have all of the necessary enzymes needed to undergo the cycle. b. This pathway allows the overall conversion of acetyl-coa molecules to oxaloacetate. c. This pathway makes it possible for plants to survive with fatty acids as the cell s only carbon source. d. Three enzymes of this pathway are also present in the glycolysis pathway. e. Succinate formed in the glyoxylate cycle can be transported to the mitochondria and enter the TCA cycle. 13. In the synthesis of purine ribonucleotides, a. a glutamine molecule is incorporated into the purine ring. b. the purine base is synthesized before the ribose phosphate moiety is added. c. the starting material is a product of the pentose phosphate pathway. d. inosine monophosphate (IMP) is synthesized and rapidly converted to CTP and UTP. 14. Which of the following statements about regulation of nucleotide biosynthesis is false? a. The enzyme amidophosphoribosyl transferase binds ATP, ADP and AMP at one inhibitory site. b. The enzyme amidophosphoribosyl transferase binds GTP, GDP and GMP at one inhibitory site. c. AMP and GMP are competitive inhibitors of IMP. d. AMP and GMP levels are balanced in that [ATP] increases GMP synthesis and [GTP] increases AMP synthesis. e. None of the above statements are false. 15. Which amino acid is exclusively ketogenic? a. phenylalanine b. leucine c. tyrosine d. tryptophan e. valine

4 16. Which of the following statements is not true of the urea cycle? a. Urea is synthesized in the liver. b. The individual steps of the urea cycle take place in both the mitochondria and the cytosol. c. Carbamoyl phosphate synthetase (CPS) contains a long tunnel in which intermediates are channeled from one active site to another. d. The final reaction of the cycle involves the hydrolysis of aspartate to yield urea and ornithine. 17. Which of the following amino acids are degraded to α-ketoglutarate? a. Ala, Cys, Gly, Ser, Thr b. Asn, Asp c. Arg, Glu, Gln, His, Pro d. Ile, Met, Val e. Leu, Lys 18. In the glucose-alanine cycle, nitrogen is transported from the muscle to the liver. What is the α-keto acid substrate used for muscle aminotransferases? a. oxaloacetate b. α-ketoglutarate c. pyruvate d. acetyl-coa e. oxalosuccinate 19. With amino acid deamination, the enzyme glutamate dehydrogenase uses what coenzyme(s)? a. NAD + b. NADP + c. PLP d. both a and b c. both b and c 20. Ketogenic amino acids are broken down and subsequently converted to. (Indicate all the apply.) a. acetyl-coa b. carbohydrates c. fatty acids d. pyruvate e. ketone bodies

5 1. pyruvate A (10 pts.) Using the diagram on the right, fill in the missing information and then answer the following questions. Answer NONE if that is an appropriate answer. Assume the cycle only goes in the forward direction. a.which step(s) produce FADH 2 b.which step(s) produce NAD + 8 malate 7 6 succinate 5 succinyl-coa B 1 4 citrate 2 isocitrate 3 c.which reaction(s) use TPP as a cofactor d. Which step(s) directly generates a high energy phosphate bond e. Arrange the following reactions of the pyruvate dehydrogenase complex (PDC) in the order they occur.

6 2. (10 pts) Cofactors: Put the following reaction steps of transamination in the correct order (you may need to use some letters more than once). a. Pyridoxamine-MP forms Schiff base with carbonyl group of the new α-keto acid b. Hydrolysis releases the amino acid and pyridoxal phosphate c. Hydrolysis releases the keto acid and pyridoxamine monophosphate d. Pyridoxal phosphate forms Schiff base with α-amino group of amino acid e. α-keto acid leaves active site and is replaced by another α-keto acid f. Rearrangement of double bond d Draw the structure of PLP in Schiff base linkage with the amino acid alanine. Use an arrow to indicate the pair of electrons from the alpha-c that would be involved in the rearrangement of the double bonds referred to in step (f) above. In the boxes at left, identify/name the compounds shown (abbreviations are OK) and circle the functional part of the molecule in its reaction chemistry.

7 3. (10 pts) Place the following components in order of occurrence as electrons flow from NADH through the ET system: a. oxygen b. CoQ c. FMN d. Cytochrome c e. NADH f. Cytochrome b g. Cytochrome a h. Cytochrome a3 e f a Which are the mobile electron carriers within ET? What is a respiratory blocker? Name one example. What is an uncoupler? Name one example. Briefly explain the chemiosmotic coupling theory for ATP synthesis.

8 4. (10 pts) Lipid Metabolism: Briefly explain the role of carnitine in fatty acid oxidation. If a 17-carbon fatty acid goes through just β-oxidation, what are the products? 17-C fatty acyl-coa acetyl-coa + FADH 2 + NADH + Distinguish how the following differ in fatty acid oxidation versus fatty acid synthesis? Location Thioester Redox coenzymes Beta oxidation Fatty Acid Synth. Briefly explain the regulation of fatty acid synthesis.

9 5. (4 pts) Sketch the Z -scheme of plant photosynthesis illustrating the flow of electrons. Include in your sketch the following: Water / P700 / P680 / Ferredoxin / NADPH / Plastoquinone / Cyt b 6 f / and Plastocyanin (6 pts) a) Starting with simple precursors such as HCO 3 -, etc., illustrate the order of nucleotides leading to the synthesis of dttp. b) Why there is therapeutic interest in developing drugs to target this pathway, name one such drug and show how it inhibits the process.

10 6. (10 pts) Glucose and glycogen are major carbohydrate fuels. Fructose-2,6-bisphosphate, along with hormones such as glucagon and insulin all play major roles in the regulation of carbohydrate metabolism. Briefly discuss the regulation of carbohydrate metabolism and the interplay of these regulators. You may include a sketch if you wish to do so.