AY2022 Semester 2 A223 ESE Biochemistry Exam PDF

AY2022 Semester 2 Name A223 ESE Student ID Assessment Seat Venue Number A223 Biochemistry...

AY2022 Semester 2 Name A223 ESE Student ID Assessment Seat Venue Number A223 Biochemistry AY2022 Semester 2 End-Semester Examination (ESE) Instructions to student: This Segment is to be used by staff grader(s) only. 1) For this question paper, there are 24 Question Marks Max pages (including this cover page). Number Awarded Marks 2) Note that textbooks are not allowed. Section A/Q1 1 You may refer to paper-based notes (in bound form, and no larger than Section A/Q2 1 A4 size) during the assessment. Section A/Q3 1 This segment is to be used by the invigilator Section A/Q4 1 only and for 'online' and 'online and paper' mode assessments only. Section A/Q5 1 Please tick the box below if the student Invigilator's Invigilator's Section A/Q6 1 has done part of the Name: Signature: assessment online: Section A/Q7 1 Partially done Section A/Q8 1 online Section A/Q9 1 Section A/Q10 1 Section A/Q11 1 Section A/Q12 1 Section A/Q13 1 Section A/Q14 1 Section A/Q15 1 Section A/Q16 1 Section A/Q17 1 Section A/Q18 1 Section A/Q19 1 Section A/Q20 1 Section A/Q21 5 DO NOT write below this line 10/30/2020 9:05:32 AM Page 1 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Assessment Seat Venue Number Section B/Q22 9 Section B/Q23 6 Section B/Q24 6 Section B/Q25 6 Section B/Q26 8 Total 60 DO NOT write below this line 10/30/2020 9:05:32 AM Page 2 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Full Marks: 60 Section A (21 Questions) Maximum Marks for This Section: 25 Question 1 (1 mark) Figure 1 shows a biochemical reaction occurring in muscle cells. Which of the following statements about the reaction in its forward direction is FALSE? (A) The reaction occurs after glycolysis. (B) The reaction is exergonic. (C) Pyruvate undergoes oxidation. (D) An electron carrier is regenerated. Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 3 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 2 (1 mark) Krebs cycle is different from glycolysis as it ____________________________. (A) does not produce carbon dioxide (B) is a linear metabolic pathway (C) does not require dehydrogenase enzyme (D) can only operate in the presence of oxygen Answer: ( ) Question 3 (1 mark) Oxidative phosphorylation differs from substrate-level phosphorylation as it____________________________. (A) produces less ATP for the same amount of substrate (B) only takes place in cytosol (C) does not require any enzyme (D) involves electron transfer, oxidation and reduction reactions Answer: ( ) Question 4 (1 mark) The coupled reaction is best described as a/an ________________ reaction. (A) exergonic (B) endothermic (C) exothermic (D) anabolic Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 4 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 5 (1 mark) Which of the following statements about ATP in human cells is CORRECT? (A) Excessive amounts of ATP are stored in mitochondria as energy storage. (B) In glycolysis, a high energy phosphate group is transferred from a substrate to form ATP. (C) Less ATP is produced under aerobic condition compared to anaerobic condition. (D) ATP molecules are highly stable energy-carrying molecules. Answer: ( ) Question 6 (1 mark) A hexokinase enzyme is treated with concentrated hydrochloric acid. Which of the following are least likely to be affected by this treatment? (A) Hydrogen bonds (B) Van der Waal’s forces (C) Peptide bonds (D) Electrostatic interactions Answer: ( ) Question 7 (1 mark) Which of the following statement about hydrophobic interactions in protein folding is FALSE? (A) The interactions stabilizes the protein structure in an aqueous environment. (B) The hydrophobic R groups are forced to cluster and are kept away from water. (C) Hydrogen bonds are formed between hydrophilic R groups and water molecules. Amino acids with polar side chains are found in the interior core of the protein, in an (D) aqueous environment. Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 5 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 8 (1 mark) Enzymes that catalyse removal of hydrogen atoms from one substrate and addition of hydrogen atoms to another substrate are termed as _________. (A) oxidoreductases (B) transferases (C) lyases (D) ligases Answer: ( ) Question 9 (1 mark) (A) The enzyme is not sensitive to pH changes. (B) The active site of the enzyme remains intact at pH 8. (C) Substrate binds to the enzyme more at pH 9 than pH 7. (D) The enzyme is most likely resistant to heat. Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 6 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 10 (1 mark) Below are five enzymes and their corresponding Km values. Identify the option that indicates the tightest binding between the substrate and enzyme? (A) Enzyme A (Km = 3.2 x 10-6) (B) Enzyme B (Km = 1.4 x 10-4) (C) Enzyme C (Km = 9.6 x 10-6) (D) Enzyme D (Km = 1.8 x 10-5) Answer: ( ) Question 11 (1 mark) In spectrophotometry, the absorbance of the analyte is_________________. (A) inversely proportional to the diameter of cuvette (B) directly proportional to the light emitted by the spectrophotometer (C) inversely proportional to the light absorbed by the analyte (D) directly proportional to the analyte concentration Answer: ( ) Question 12 (1 mark) When using a standard curve for determining the concentration of a substance, the standard curve is NOT usable when ______________________. (A) it is a linear curve (B) the absorbance of the sample falls within the range of the absorbance of the standard (C) the concentration of the sample is higher than the highest concentration of standard (D) the standard is assayed using the same method as the sample Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 7 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 13 (1 mark) The glycogen in muscle does not contribute to the maintenance of blood glucose level as the muscle does not express the enzyme _________________. (A) transferase (B) glycogen phosphorylase (C) glucosidase (D) glucose-6-phosphatase Answer: ( ) Question 14 (1 mark) Which of the following CORRECTLY describes the action of insulin in regulation of blood glucose levels? (A) Inhibits glycogen synthesis in the liver (B) Inhibits glycolysis in both liver and muscle (C) Promotes glycogenolysis in the muscle (D) Promotes glucose uptake by both liver and muscle cells Answer: ( ) Question 15 (1 mark) Which of the following statements about blood glucose regulation is FALSE? (A) Liver has a large glycogen store to ensure a normal blood glucose level during exercise. (B) Epinephrine promotes glycogen synthesis to reduce blood glucose level after meal. (C) Gluconeogenesis increases blood glucose level during starvation. Glucagon signalling results in activation of protein kinase A to promote glycogen (D) breakdown. Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 8 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 16 (1 mark) In fatty acid synthesis, _________________ is the active donor of ___________ carbon atoms to elongate the growing fatty acid chain. (A) acetyl-CoA; two (B) acetyl-CoA; three (C) malonyl-CoA; two (D) malonyl-CoA; three Answer: ( ) Question 17 (1 mark) The gene that codes for liver aldehyde dehydrogenase is mutated in an individual. Which of the following will most likely happen during alcohol consumption by the individual? (A) Ethanol cannot be converted to acetaldehyde. (B) There is an accumulation of acetic acid in the liver. (C) There is a build-up of NADH and acetaldehyde in the liver. (D) Fatty acids synthesis from acetyl-CoA is promoted. Answer: ( ) Question 18 (1 mark) In ammonia metabolism, α-ketoglutarate is produced from glutamate in the liver through _______________________. (A) transamination (B) oxidative deamination (C) condensation (D) reduction Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 9 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 19 (1 mark) In the above redox reaction, which is an oxidizing agent? (A) Succinate (B) Fumarate (C) FAD (D) FADH2 Answer: ( ) Question 20 (1 mark) The most likely process occurring when a badminton player undergoes training for 2-hours is ___________________. (A) glycogenesis (B) fatty acid synthesis (C) ketogenesis (D) glycogenolysis Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 10 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 21 (5 marks) Question 21a (1 mark) At substrate concentration of 2.0mM and in the absence of inhibitor, all the enzyme active sites are occupied by substrate molecules. (A) True (B) False Answer: ( ) Question 21b (1 mark) From the data, a Michaelis-Menten curve can be plotted and the maximum velocity of both reactions can be determined. (A) True (B) False Answer: ( ) DO NOT write below this line 10/30/2020 9:05:32 AM Page 11 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 21c (1 mark) The inhibitor is likely to be a competitive inhibitor. (A) True (B) False Answer: ( ) Question 21d (1 mark) In both reactions, product formation increases as the substrate concentration increases from 0.2 to 1.2 mM. (A) True (B) False Answer: ( ) Question 21e (1 mark) The reaction without inhibitor produces more products than the reaction with inhibitor at any given substrate concentration. (A) True (B) False Answer: ( ) END OF SECTION A DO NOT write below this line 10/30/2020 9:05:32 AM Page 12 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Section B (5 Questions) Maximum Marks for This Section: 35 Answer ALL Questions in this Section B; Total Marks: 35 marks Write your answers clearly in the spaces provided. Question 22 (9 marks) Patient A suffers from McArdle disease (muscle glycogen phosphorylase deficiency). He has muscle cramps and extreme tiredness after physical exercise. His blood lactate concentration after exercise is shown in Figure 3. The results from a normal, healthy individual (Control) is also shown in the graph. a. Explain why Patient A experiences muscle pain and extreme tiredness after exercise. (2 marks) b. After exercise, blood lactate concentration was increased in the control patient but not in Patient A. Explain why this is so. (3 marks) c. Patient A has taken a meal, and his muscle glycogen level was tested 4 hours later. Will you expect his level of muscle glycogen to be low, normal or high? Explain. (2 marks) d. His doctor has advised Patient A to consume glucose supplements frequently while exercising. How would this help alleviate his discomfort during and after exercise? (2 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 13 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID DO NOT write below this line 10/30/2020 9:05:32 AM Page 14 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 23 (6 marks) a. A migrating bird stores higher amounts of triglycerides than glycogen in its body. Explain how this composition of fuel sources is beneficial for the bird’s long-distance migration. (2 marks) b. Lignoceric acid is a fatty acid with 24 carbons per molecule. How many molecules of ATP will be produced through a complete beta-oxidation of 1 molecule of lignoceric acid? Show your working clearly. (4 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 15 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 24 (6 marks) Answer the following questions according to the figure provided. Question 24a (2 marks) Figure 4 illustrates processes involved in the formation and removal of reactive oxygen species (ROS). DO NOT write below this line 10/30/2020 9:05:32 AM Page 16 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID With reference to Figure 4, identify the processes that lead to the formation of reactive oxygen species. (2 marks) Question 24b (4 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 17 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Figure 5 illustrates the peroxidation of unsaturated lipids leading to the formation of lipid peroxyl radicals (ROO·) in biological systems. i. Explain the role of Vitamin E as an antioxidant. (1 mark) ii.Explain the role of Vitamin C in the prevention of lipid peroxidation. (3 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 18 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 25 (6 marks) a. Build-up of ammonium ion in the blood results in ammonia crossing the blood-brain barrier. In the brain ammonia is used to make glutamate, depleting the brain of α-ketoglutarate. Explain why this would result in neural cell damage and cell death. (2 marks) b. Given the following information about two newborn infants who appeared normal at birth but developed hyperammonemia after 24 hours, determine which urea cycle enzyme(s) might be defective in each case. (4 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 19 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID i. Infant A had low levels of blood urea nitrogen and high levels of ammonia, argininosuccinate, and citrulline in the blood. ii. Infant B had elevated plasma glutamine and low citrulline levels in the blood. DO NOT write below this line 10/30/2020 9:05:32 AM Page 20 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID Question 26 (8 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 21 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID a. Identify the metabolic Pathways A, B and C in Figure 6. (2 marks) b. Type I diabetics do not produce any insulin and therefore the glucose cannot enter the cells. State whether metabolic Pathways B and C will be functional / non-functional in a type 1 diabetic individual. Support your answers with explanations. (4 marks) c. Why is the brain able to use ketone bodies under starvation conditions? (2 marks) DO NOT write below this line 10/30/2020 9:05:32 AM Page 22 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID DO NOT write below this line 10/30/2020 9:05:32 AM Page 23 of 24 2220ESEA223MainA001X00001x  AY2022 Semester 2 Name A223 ESE Student ID END OF SECTION B End of Assessment DO NOT write below this line 10/30/2020 9:05:32 AM Page 24 of 24 2220ESEA223MainA001X00001x