Lebanese International UniversitySchool of Arts and Sciences

Department ofBiological and Chemical Sciences

I- Choose the ONE correct answer from the following multiple choice questions and MARK YOUR CHOICE ON THE ANSWER SHEET on the LAST PAGE of the exam:

Page 1 of 1 BIOC310-Spring 2012-2013-ExamII

1. If the triose phosphate isomerase is inhibited then: A. The end product of glycolysis would be 2 pyruvatesB. The net yield of glycolysis would be 2 ATPC. The net yield of glycolysis would be reduced to zeroD. Only 2 NADH would be produced from glycolysisE. All of the above are correct

2. The conversion of ribulose-5-phosphate to xylulose-5-phosphate requires what enzyme?A. phosphopentose isomeraseB. phosphopentose epimeraseC. transketolaseD. transaldolaseE. lactonase3. A patient is suffering from a metabolic disorder in which his glucokinase has a greatly diminished Vmax such that its value is similar to that of his normal hexokinase. What would be one evident symptom for this patient? A. Will be hypoglycemic during times of starvation B. Will be hyperglycemic after eating a baked potato C. Will be hypoglycemic after eating a baked potato D. Will be hyperglycemic during times of starvation E. The disorder will not affect his ability to maintain normal blood sugar following a meal.

4. Which of the following is the primary function of the pentose phosphate pathway in the red cell?A. Provision of ribose for synthesis of ribonucleic acid.B. Provision of deoxyribose for synthesis of deoxyribonucleic acid.C. Synthesis of NADPH for electron transport.D. Synthesis of NADPH for maintenance of antioxidant defensesE. Synthesis of NADPH for biosynthesis of fatty acids and cholesterol

5. ____________ is the only enzyme in glycolysis that catalyzes a reversible reaction, that generates a high energy bond and that do not need to be bypassed in gluconeogenesis is: A. Hexokinase B. Pyruvate kinase C. Phosphofructokinase-1 D. Phosphoglycerate kinaseE. Phosphoglucoisomerase

6. The conversion of 3-phosphoglycerate to phosphoenolpyruvate requires two reactions. Which of the following correctly identifies the types of reactions in the proper order of glycolysis?A. isomerization, hydrationB. hydration, isomerizationC. dehydration, isomerizationD. isomerization, dehydrationE. mutation, dehydration

7. Starting with glyceraldehyde 3-phosphate and synthesizing one molecule of pyruvate, the net yield of ATP and NADH would be which of the following?A. 1 ATP, 1 NADHB. 1 ATP, 2 NADHC. 1 ATP, 4 NADHD. 2 ATP, 1 NADHE. 2 ATP, 2 NADH

8. As a cancer cell grows into a tumor, it needs a lot of nucleic acids (i.e. Ribose 5-P) and synthesis power (i.e. NADPH). Which of the following enzymes are not required to meet these needs?A. HexokinaseB. Glucose 6-phosphate dehydrogenaseC. Ribulose 5-phosphate isomeraseD. 6-phosphogluconate dehydrogenaseE. Transketolase

9. Which of the following glycolytic liver enzymes is NOT product-inhibited and is absent in muscle cells? A. HexokinaseB. EnolaseC. AldolaseD. GlucokinaseE. Glucose-6-phosphatase

10. The cancer cells are widely dependent on glycolysis to meet their energy needs. Which of the following statements must also be true in a cancer cell to achieve their needs? A. Fructose 2,6-bisphosphate will be low in the cancer cellB. Phosphoenolpyruvate carboxykinase will be activeC. Glucose 6-phosphatase will be activeD. Phosphofructokinase 2 will be activeE. Pyruvate will be turned into oxaloacetate in the matrix of the mitochondria

11. If unregulated, which of the following pairs of enzymes would represent a unsuccessful cycle?A. pyruvate kinase and pyruvate carboxylaseB. pyruvate carboxylase and phosphoenolpyruvate carboxykinase C. pyruvate kinase and fructose-1,6-bisphosphataseD. fructose-1,6-bisphosphatase and phosphofructokinaseE. glucose-6-phosphatase and phosphofructokinase

12. Lactate dehydrogenase (LDH) plays an essential role in an exercising muscle, especially when the level of excursion surpasses the ability of circulatory systems ability to supply adequate oxygen. Why LDH is so important to the muscle under these conditions?A. It produces one mole of ATP via substrate level phosphorylation.B. It decreases pH thus decreasing the dissociation rate of oxygen from hemoglobinC. It removes excess lactic acid from the muscle to create pyruvateD. It produces NADH for energy while converting pyruvate into lactateE. It resupplies NAD+ to glyceraldehyde 3-phosphate dehydrogenase13. The term substrate level phosphorylation applies to which glycolytic reactions? A. Enolase and pyruvate kinase B. Pyruvate kinase and phosphoglycerate kinase C. Phosphoglycerate kinase and phosphoglycerate mutase D. Glucokinase and phosphoglucose isomerase E. Triose phosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase

Oxidative metabolism:14. Cyanide will cause rapid death in humans because it:A. Stops glycolysis.B. Stops the TCA cycle from turning.C. Stops the electron transport chain at coenzyme Q.D. Blocks cytochrome c oxidase.E. Inhibits the ATP synthase.

15. You isolate mitochondria from a patient suffering from muscle weakness and lactic acidosis. You determine that the patient is UNABLE to oxidize ubiquinol; he is also unable to pump protons across the inner membrane if succinate or cytochrome c are given. This patient most likely suffers from a defect in which of the following protein complexes?A. Complex IB. Complex IIC. Complex IIID. Complex IVE. Complex V, ATP synthase

16. In a coupled mitochondria which of the following would you expect to observe?A. Oxygen uptake should stop when ADP is lowB. The addition of oligomycin will not affect oxygen consumptionC. The ratio ATP/O2 consumed (i.e. P/O ratio) is the same for FADH2 and NADHD. The membrane potential will be unaffected by 2,4-DNPE. Increased membrane potential upon exposure to rotenone17. A patient was poisoned with antimycin, what would you expect to find if you could isolate their mitochondria and assay them for their response to 2,4-dinitrophenol (2,4-DNP) and their pools of cofactors? Response to 2,4-DNP Cofactors A. Oxygen consumption restored Increased QH2 B. Oxygen consumption restored Increased reduced cytochrome C C. Oxygen consumption unchanged Increased NADH D. Oxygen consumption unchanged Increased QH2 E. Oxygen consumption unchangedIncreased reduced cytochrome C

18. Which of the following correctly indicates the number of protons pumped into the intermembrane space at each complex of electron transport for each FADH2 that is oxidized by the electron transport pathway?A. II: 2 III: 4 IV: 2B. II: 0 III: 2 IV: 4C. II: 2 III: 2 IV: 2D. II: 0 III: 4 IV: 2E. II: 0 III: 2 IV: 2

19. Heat can be generated in the brown adipose tissue of hibernating mammals due to ________.A. increased ATP production by ATP synthaseB. uncoupling by thermogeninC. a greater pH gradient across the inner mitochondrial membrane by complex IVD. insufficient NADH production during the citric acid cycle due to less active pyruvate translocase.E. None of the above

20. A patient with chronic fatigue. The results of her blood tests suggest that her blood cell count is low because of iron deficiency anemia. Such a deficiency would lead to fatigue because of which of the following?A. Her decrease in Fe-S centers is impairing the transfer of electron in the electron transport chainB. She is not producing as much H2O in the electron transport chain, leading to dehydration, which has resulted in fatigueC. Iron forms a chelate with NADH and FADH2 that is necessary for them to donate their electrons to the electron transport chainD. None of the above E. All of the above

Glycogen metabolism and gluconeogenesis21. The precursor to glycogen in the glycogen synthase reaction is:A. Glucose-1-PB. Glucose-6-PC. UDP-GlucoseD. UTP-GlucoseE. None of the above

22. A 23 year old man is unable to exercise vigorously without developing muscle cramps. Studies of his exercising forearm reveal that during maximal work, he does not produce lactate. This individual most likely has a deficiency of A. fructose 1,6 bisphosphatase. B. PEP carboxykinase. C. pyruvate dehydrogenase. D. glycogen debranching enzyme. E. glycogen phosphorylase.

23. The active form of glycogen ___ is phosphorylated, while the active form of glycogen ___ is dephosphorylated:A. Hydrolase, dehydrogenaseB. Dehydrogenase, hydrolaseC. Hydrolase, transketolaseD. Phosphorylase, synthaseE. Synthase, phosphorylase

24. When glucagon binds to receptors on mammalian liver cells, which of the following occurs due to enzyme phosphorylation?A. activation of PFK-2 followed by activation of glycolysisB. activation of FBPase followed by inhibition of gluconeogenesisC. activation of PFK-2 followed by activation of gluconeogenesisD. activation of FBPase followed by activation of gluconeogenesisE. activation of PFK-2 followed by inhibition of glycolysis25. Which choice (A E) for filling in the blanks makes a true statement? In the regulation of glycogenolysis in liver cells, binding of the hormone _____X______ leads to the release of the second messenger ______Y_______ that is responsible for initiating the reactions that lead to the conversion of glycogen to glucose 1-phosphate. A. Epinephrine, insulin B. Insulin, Ca2+ C. Acetylcholine, glucagon D. Glucagon, adenylate cyclase E. Glucagon, cAMP

26. Following 3 days fast (i.e you are completely devoid of glycogen stores), which of the following lists the components that are required for making glycogen following a carbohydrate rich meal?A. Glycogen phosphorylase, glycogenin, and glycogen synthaseB. Glycogen synthase, UDP-Glucose pyrophosphoryalse, and glucokinaseC. Glycogenin, glycogen phosphorylase, and debranching enzymeD. Debranching enzyme, glycogen synthase, and glycogeninE. Branching enzyme, UDP-Glucose pyrophosphorylase, and glycogen phosphorylase

27. Which enzyme is used in gluconeogenesis but not in glycolysis? A. Phosphoglucoisomerase B. Lactate dehydrogenase C. Glucose 6-phosphatase D. 3-Phosphoglycerate kinase E. Aldolase

28. The conversion of mitochondrial oxaloacetate to cytosolic phosphoenolpyruvate involves all of the following EXCEPT: A. Malate transporter B. Malate dehydrogenase C. GTP D. Fumarase E. Phosphoenolpyruvate carboxykinase

29. There are several gluconeogenic enzymes that are critical to overcome essentially irreversible steps in glycolysis. Which of the following gluconeogenic enzymes is NOT matched with the glycolytic enzyme that it overcomes? Gluconeogenic GlycolyticA. Pyruvate carboxylase Pyruvate kinaseB. Fructose 1,6-bisphosphatase Phosphofructokinase 1 C. Phosphoenolpyruvate carboxykinase Pyruvate kinaseD. Glucose 6-phosphatase HexokinaseE. Pyruvate carboxylase Phosphoglycerate kinase

30. A patient is undergoing a cleansing diet and has not eaten in about 36 hours. He has become forgetful and seems out of it. He is quickly diagnosed as hypoglycemic and you conclude that the patients gluconeogenic pathway is defective. Upon further investigation, you determine the patient has high circulating levels of alanine, pyruvate, and lactate. You also realize there is little if any oxaloacetate being produced and biotin supplements seem to alleviate most of the symptoms. Which of the following enzymes is most likely defective in the patient?A. Pyruvate carboxylaseB. Phosphoenolpyruvate carboxykinaseC. Malate dehydrogenaseD. Fructose 1,6-bisphosphataseE. Glucose 6-phosphatase

31. In a person with a deficiency of fructose 1,6-bisphosphatase, the predominant metabolic consequence is:A. failure to synthesize glucose from lactic acidB. failure to split fructose 1,6-bisphosphate into triose phosphatesC. inability to degrade glycogenD. inability to fix CO2 into organic linkagesE. lowered yield of ATP production per mole of glucose metabolized

32. What is the major mechanism for inhibition of glycolysis in liver during gluconeogenesis?A. GK is inhibited by the high concentration of Glc-6-P.B. Phosphorylation of PFK-2/Fru-2,6-BPase leads to decreased levels of Fru-2,6-BP, which is an allosteric activator of PFK-1.C. Increased hepatic acetyl-CoA inhibits the activity of PDH.D. Hydrolysis of Glc-6-P to glucose decreases the availability of Glc-6-P for glycolysis.E. Phosphorylation of PFK-2/Fru-2,6-BPase leads to decreased levels of Fru-2,6-BP, which is an allosteric inhibitor of PFK-1.

TCA cycle:33. If the concentration of ATP is low, the availability of glucose and acetyl-CoA is high, and no other metabolic demands are made on the cell, what is the most likely fate of oxaloacetate?A. It is converted to phosphoenolpyruvate for gluconeogenesis to continue.B. It is polymerized in glycogenesis.C. It is converted to pyruvate.D. It is combined with acetyl-CoA and enters the TCA cycle.E. It is converted to malate through the reversal of a reaction in the TCA cycle.

34. Which of the following statements about regulation of pyruvate dehydrogenase is correct?A. PDH is activated by increasing NADH concentration in the mitochondrion.B. PDH is activated by phosphorylation by PDH kinase.C. PDH is activated allosterically by ATP.D. PDH is inactivated by phosphorylation by cAMP-dependent protein kinase.E. PDH and pyruvate carboxylase are reciprocally regulated by acetyl CoA.

35. A patient with a mitochondrial defect is brought into the clinic. You quickly deduced that her mitochondria are not producing as much NADH as a normal person suggesting a defect in the TCA (tricarboxylic acid cycle) cycle. Upon further evaluation, you determine her mitochondria have an excess succinyl CoA and a deficiency in GTP. Which of her TCA enzymes is most likely to be defective? A. -Ketoglutarate dehydrogenase B. Citrate synthase C. Fumarase D. Succinate dehydrogenase E. Succinate thiokinase (synthase)

36. Succinate dehydrogenase differs from all other enzymes in the TCA cycle in that it is the only enzyme that displays which of the following characteristics?A. It is embedded in the inner mitochondrial membrane.B. It is inhibited by NADH.C. It contains bound FAD.D. It contains Fe-S centers.E. It is regulated by a kinase.

37. A patient diagnosed with thiamine deficiency exhibited fatigue and muscle cramps. The muscle cramps have been related to an accumulation of metabolic acids. Which of the following metabolic acids is most likely to accumulate in a thiamine deficiency?A. Isocitric acidB. Pyruvic acidC. Succinic acidD. Malic acidE. Oxaloacetic acid

38. A patient suffering from an isocitrate dehydrogenase deficiency is most likely to exhibit which of the following?A. Increased level of -ketoglutarateB. Decreased electron transport chain activityC. Increased levels of glutamateD. Normal NADH levels within the matrixE. Decreased levels of isocitrate

39. Which of the following enzymes of the pyruvate dehydrogenase complex is responsible for the oxidation of the hydroxyethyl group from pyruvate decarboxylation to an acetyl group?A. pyruvate dehydrogenaseB. dihydrolipoamide transacetylaseC. dihydrolipoamide dehydrogenaseD. pyruvate dehydrogenase kinaseE. pyruvate dehydrogenase phosphatidase

40. Arsenic poisoning by either arsenite or organic arsenical agents work by binding to dithiol compounds such as _________ meaning that in addition to inactivation of pyruvate dehydrogenase, the citric acid cycle enzyme _________ would be inactivated.A. cysteine; aconitaseB. coenzyme A; -ketoglutarate dehydrogenaseC. coenzyme A; citrate synthaseD. thiamine pyrophosphate; isocitrate dehydrogenaseE. lipoamide; -ketoglutarate dehydrogenase

41. Which of the following is an inhibitor of pyruvate dehydrogenase, isocitrate dehydrogenase, and -ketoglutarate dehydrogenase?A. NADHB. succinyl-CoAC. ATPD. acetyl-CoAE. none of the above

Page 8 of 8 BIOC310-Spring2012-2013- Exam1

Part II- Subjective Questions

Question I: Briefly explain why and where the NADH of glycolysis yields 2 or 3 ATPs when entering the Electron transport chain. The students should explain the G3P and malate/aspartate shuttles and where they are used (muscle and heart and other tissues)

Question II: Can the muscles glycogen be mobilized to replenish blood glucose in the case of hypoglycemia? Explain why and indicate how the response to glucagon could be terminated in liver cells.

No it cannot. Gluconeogenesis is activated by glucagon and needs, among others, the Glc-6-Pase to bypass the irreversibility of the hexokinase. Muscle is rich in glycogen, but it lacks both the glucagon receptor and Glc-6-Pase.

Question III: Give 2 examples of enzymes whose deficiencies lead to hemolytic anemia. Briefly explain.

Glucose-6-Phosphate dehydrogenase: the decreased activity of this enzyme leads to the impairment of the pentose phosphate pathway, therefore to a decrease in the production of NADPH. Thus the ability of the cell to recycle the GSH from GSSG by the glutathione reductase is impaired. This leads to the lysis of the red blood cells under any oxidative stress.

Pyruvate Kinase: The hemolytic anemia in this case is due to the inability of the cell to produce enoQuestion IV: Define Von Gierkes disease, mucopolysaccaridoses and galactosemia indicating the deficient enzyme and the consequences of this deficiency.

Question V: Explain why fluorocitrate, a potent inhibitor of the enzyme aconitase, is a deadly poison.

GOOD LUCK