2023-Midterm

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Queens University *

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316

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Chemistry

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Feb 20, 2024

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1 QUEEN'S UNIVERSITY MID-TERM TEST Wednesday FEBRUARY 15 th , 2023 BCHM 310/316* 5:30pm – 6:20pm FACULTY OF ARTS AND SCIENCE DEPARTMENT OF BIOMEDICAL AND MOLECULAR SCIENCES Course Coordinator: Dr. G. Jones INSTRUCTION AND NOTES TIME ALLOWED : 50 minutes There are 25 questions. Answer ALL of them. Each question carries the same mark. There is no penalty for an incorrect answer. For each question indicate the best or most appropriate answer by blackening, IN PENCIL , the appropriate vertically-dotted area on the ANSWER SHEET . Incorrect answers may be erased. Write your NAME or STUDENT IDENTIFICATION NUMBER and COURSE NUMBER (310 or 316*) on the multiple choice answer sheet. Finally, hand in the SCANTRON ANSWER SHEET and MID-TERM TEST QUESTIONS. You will get a chance to check your answers later with the correct answer Scantron.

2 SECTION A For each question in this section, blacken the area that corresponds to the BEST answer. A single answer is required for each question. 1. Which of one the following combinations A-E CORRECTLY matches the monosaccharides shown in structures 1-5 below? A. Structure 1 = Galactose; Structure 2 = Glucose; Structure 3 = Fructose B. Structure 2 = Fructose; Structure 3 = Mannose; Structure 4 = Ribose C. Structure 4 = Ribulose; Structure 5 = Glucose; Structure 1 = Mannose D. Structure 1 = Glucose; Structure 3 = Galactose; Structure 5 = Mannose E. Structure 3 = Glucose; Structure 4 = Ribose; Structure 5 = Fructose 2. Erythrocytes possess which one of the following enzymes: A. pyruvate kinase B. pyruvate dehydrogenase C. isocitrate dehydrogenase D. b -hydroxybutyrate dehydrogenase E. malate dehydrogenase 3. Glucagon upregulates or leads to activation of which of the following enzymatic steps OR proteins: A. GLUT-4 glucose transporters B. glucokinase/hexokinase IV C. phosphoprotein phosphatase 1 (PP1) D. fructose-2,6-bisphosphatase-2 (FBPase-2) E. glycogen synthase 1 2 3 4 5

3 SECTION A For each question in this section, blacken the area that corresponds to the BEST answer. A single answer is required for each question. 4. In the sequence of steps in the mid to latter stages of glycolysis, which of the following steps involves substrate-level phosphorylation ? A. Fructose-6-phosphate -> Fructose-1,6-Bisphosphate B. Glyceraldehyde-3-Phosphate -> 1,3-Bisphosphoglycerate C. 1,3-Bisphosphoglycerate -> 3-Phosphoglycerate D. 3-Phosphoglycerate -> 2-Phosphoglycerate E. 2-Phosphoglycerate -> Phosphoenolpyruvate (PEP) 5. Which of the following statements about glycogen synthase is INCORRECT : A. it is directly phosphorylated by protein kinase A B. it is activated by insulin in the hepatocyte C. it involves inactivation of GSK-3 (glycogen synthase kinase-3) D. it requires glucose-1-P to be energized by UTP E. it adds glucose molecules to non-reducing ends of the growing chains by forming ( a 1->4) linkages 6. Which of the following statements about the citric acid cycle is INCORRECT: A. it directly generates 1 GTP (or ATP), 3 NADH and 1 FADH 2 per cycle B. it stops in the liver during starvation for the organ to carry out gluconeogenesis C. it involves four dehydrogenase enzymes D. it is dependent on a constant supply of oxaloacetate provided by anaplerotic pathways E. it directly generates 2 water molecules per acetyl CoA 7. The structure shown below is: A. glutathione B. carnitine C. a bile salt D. choline E. ethanolamine

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4 SECTION A For each question in this section, blacken the area that corresponds to the BEST answer. A single answer is required for each question. 8. Using the compositional data in the table below select the combination which best fit lipoprotein particle descriptors for Lipoprotein A & B respectively: A. LDL and VLDL B. VLDL and Chylomicrons C. VLDL and LDL D. Chylomicrons and LDL E. Chylomicrons and VLDL 9. Which of the following is a (are) high energy phosphate bond(s) A. adenosine - a PO 4 bond only B. a PO 4 - b PO 4 bond only C. b PO 4 - g PO 4 bond only D. both adenosine - a PO 4 bond and a PO 4 - b PO 4 bond E. both a PO 4 - b PO 4 bond and b PO 4 - g PO 4 bond 10. Which of the following statements regarding ketogenesis/ketone body utilization is CORRECT: A. ketone bodies are made exclusively in the liver and kidney B. ketogenesis involves the mitochondrial enzyme HMG-CoA synthase C. ketogenesis is absent in individuals with myopathic carnitine deficiency D. ketone body use by the liver depends upon oxaloacetate supply by pyruvate carboxylase E. ketone body utilization is absent from the brain due to the blood-brain barrier

5 SECTION A For each question in this section, blacken the area that corresponds to the BEST answer. A single answer is required for each question. 11. Muscle contains which of the following combinations of transporters, enzymes and receptors: A. GLUT2, hexokinase I and ONLY the glucagon receptor B. GLUT4, hexokinase IV and BOTH glucagon and epinephrine receptors C. GLUT2, hexokinase IV and ONLY the glucagon receptor D. GLUT4, hexokinase I and ONLY the epinephrine receptor E. GLUT2, hexokinase IV, and BOTH glucagon and epinephrine receptors 12. Which of the following structures is a (are) ketone body (ies): A. Structure 1 only B. Structure 2 only C. Structure 3 only D. Structures 1 & 2 E. Structures 1 & 3 13. The lipid structure below is best classified as: A. 1-stearoyl, 2-linolenoyl phosphatidyl ethanolamine B. 1-palmitoyl, 2-linoleoyl phosphatidyl choline C. 1-palmitoyl, 2-linoleoyl phosphatidyl ethanolamine D. 1-palmitoyl, 2-linolenoyl phosphatidyl serine E. 1-stearoyl, 2-linolenoyl phosphatidyl choline END OF SECTION A 14

6 SECTION B For the following questions, ONE or MORE of the statements are correct. Indicate on your answer sheet which letter A through E is the correct answer. (A) if only 1, 2 and 3 are correct. (B) if only 1 and 3 are correct. (C) if only 2 and 4 are correct. (D) if only 4 is correct. (E) if ALL are correct. 14. The carnitine transport system for fatty acids: 1. requires two pools of CoA in the cytoplasm and the mitochondrial matrix 2. exists to help fatty acids to traverse the impermeable outer mitochondrial membrane 3. is down regulated by malonyl CoA levels 4. transports fatty acids with a range of chain lengths from C 12 to C 22 15. Peroxisomal β-oxidation of fatty acids involves : 1. oxidation of medium chain (>C 10 -C 14 ) fatty acids 2. export of NADH + H + to mitochondria for reoxidation to NAD 3. regeneration of FAD using the enzyme catalase to reoxidise the FADH 2 4. export of acetyl CoA to mitochondria to enter the citric acid cycle 16. The steps of mitochondrial β-oxidation of fatty acids to acetyl CoA : 1. directly releases about 75% of the available energy as ATP 2. involves two dehydrogenation (oxidation) steps each generating NADH 3. directly releases 1 water molecule per β-oxidation cycle 4. occurs while the fatty acid is attached to coenzyme A 17. The action of adipocyte lipases involves: 1. lipolysis of the triglyceride to three “free” fatty acids and glycerol 2. recycling of the glycerol backbone by glycerol kinase in the adipocyte 3. direct phosphorylation of perilipin and activation of a lipase by protein kinase A 4. transport of the fatty acids on LDL back to the liver 18. Muscle carries out glycogenolysis and glycolysis during fasting because: 1. muscle lacks glucagon receptors so cannot inhibit glycolysis 2. muscle lacks glucose-6-phosphatase 3. muscle needs glycolysis to generate energy from the G-6-P formed during glycogenolysis 4. muscle exports pyruvate to the liver as part of the Cori cycle

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7 SECTION B For the following questions, ONE or MORE of the statements are correct. Indicate on your answer sheet which letter A through E is the correct answer. (A) if only 1, 2 and 3 are correct. (B) if only 1 and 3 are correct. (C) if only 2 and 4 are correct. (D) if only 4 is correct. (E) if ALL are correct. 19. Which of the following enzymes/pathways is (are) CORRECTLY listed with one of its (their) regulators : 1. pyruvate carboxylase- acetyl CoA 2. glycogen phosphorylase a - glucose 3. pentose phosphate pathway- NADPH 4. pyruvate dehydrogenase- [NADH/NAD] ratio 20. Which of the following enzymes depends upon pyrophosphatase for energy needed to drive it : 1. glucose-6-phosphatase 2. fatty acyl CoA synthetase 3. fructose-1,6-bisphosphatase 4. UDP-glucose pyrophosphorylase 21. Which coenzymes of Pyruvate Dehydrogenase bind the substrate or release the product: 1. NAD 2. thiamin pyrophosphate (TPP) 3. FAD 4. lipoic acid 22. Human Glucose-6-Phosphate Dehydrogenase deficiency results in : 1. compromised NADPH production for antioxidant defenses 2. reduced biosynthesis of ribose-5-phosphate needed for nucleic acid biosynthesis 3. increased sensitivity to chemotherapeutic drugs 4. decreased protection from malaria in mosquito-affected areas

8 SECTION B For the following questions, ONE or MORE of the statements are correct. Indicate on your answer sheet which letter A through E is the correct answer. (A) if only 1, 2 and 3 are correct. (B) if only 1 and 3 are correct. (C) if only 2 and 4 are correct. (D) if only 4 is correct. (E) if ALL are correct. 23. Which of the following statements about the synthesis of docosahexaenoic acid (DHA) from an essential fatty acid in mammals is (are) CORRECT: 1. the initial steps alternate between firstly a) desaturation and then b) elongation steps 2. desaturation steps involve sequentially: Δ 6 -desaturase, Δ 5 -desaturase & Δ 6 -desaturase again 3 . it starts with 18:3Δ 9,12,15 and involves the intermediate 24:6Δ 6,9,12,15,18,21 4. the final step involves removal of a C-2 unit by mitochondrial β-oxidation 24. The regulation of glycolysis/gluconeogenesis is mainly through the action of insulin: 1. activating phosphofructokinase-2 activity in a bifunctional (PFK-2/FBPase-2) enzyme 2. by causing a dephosphorylation event which inactivates FBPase-2 3. thereby generating increased concentrations of the activator, fructose-2,6-bisphosphate 4. which up-regulates glycolysis and down-regulates gluconeogenesis 25. During the later stages of fasting the brain becomes dependent upon which of the following enzymes to efficiently generate energy: 1. thiolase 2. PEP carboxykinase 3. 3β-ketoacyl CoA transferase 4. isocitrate dehydrogenase END OF TEST