BIOS5003 Biochemistry of Cell Function 2021 Exam PDF

BIOS5003 Biochemistry of Cell Function 04 May 2021 10:00 - 12:00 2 Hours Student Materials Not Permitted Do not turn over or open the examination paper until the beginning of the examination is announced This examination paper must not be removed from the examination room. The pap...

BIOS5003 Biochemistry of Cell Function 04 May 2021 10:00 - 12:00 2 Hours Student Materials Not Permitted Do not turn over or open the examination paper until the beginning of the examination is announced This examination paper must not be removed from the examination room. The paper will be published on RADAR after the exam © Oxford Brookes University 04/05/2021 Semester 2, 2020-2021 BIOS5003 BIOS5003 Biochemistry of Cell Function Examination Rubric Examination length: 2 hours. Answer three questions, one from Section A and two from Section B. Answer each question on a separate page. All questions carry equal marks, the marks shown indicate the marks for each part of the question. Page 1 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 Examination Questions Section A A1 Below is some data collected from an experiment to determine the specific activity of an enzyme from a serum sample. The data in the tables has been plotted on to graphs. Time (seconds) Abs340nm 0 0.0000 10 0.1200 20 0.2200 30 0.3000 40 0.3700 50 0.4500 60 0.5100 70 0.5500 80 0.5900 90 0.6200 0.7 0.6 0.5 Abs340nm 0.4 0.3 0.2 0.1 0.0 0 10 20 30 40 50 60 70 80 90 Time (seconds) Page 2 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 [BSA] mg ml-1 Abs595nm 0.0000 0.0000 0.1000 0.1100 0.2500 0.2600 0.5000 0.5500 0.7500 0.7400 1.0000 1.0500 Enzyme Sample (1 ml) 0.460 1.2 1.0 0.8 Abs595nm 0.6 0.4 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 [BSA] mg ml-1 a) What might be the reasons for the initial rate of rise of Abs340nm and then subsequent plateauing in the first graph? Include brief reasoning for your suggestions. 4 marks b) Calculate the specific activity of the enzyme and explain why this is a useful measure of enzyme activity. Please show all your working. 5 marks Page 3 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 c) Describe the molecular mechanisms through which competitive, non- competitive and uncompetitive inhibitors inhibit enzyme function. In your answer, explain the effects of each type of inhibitor on the Km and Vmax of an enzyme. 6 marks d) Describe the components of a modern HPLC system and how they would function to purify this enzyme from the sample. 5 marks Page 4 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 A2 a) You are attempting to size four unknown proteins (A, B, C and D). The migration distances of these proteins following SDS-PAGE is shown, along with those of a set of molecular weight standards. Using information from the table and plot below, determine the molecular weights of proteins A, B, C and D, explaining how you have done this. Marker Mr (kDa) 250 150 100 75 50 37 25 20 15 5 Migration (mm) 7 21 35 43 60 72 87 94 103 120 Protein A B C D Migration (mm) 28 52 78 96 4 marks Page 5 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 c) Describe how to visualize a protein of interest using a western blot. 8 marks d) Compare and contrast the techniques of antibody and metal affinity column chromatography, indicating when you would use each. 8 marks Page 6 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 Section B B1 a) Discuss how G protein-coupled receptors (GPCRs) and enzyme-coupled receptors differ in structure and in the mechanism by which they transduce their signal. Name one example of each of these types of receptor. 8 marks b) Why is it important to be able to switch signalling off as well as on? Describe two different negative feedback strategies that cells may use to switch activated signalling pathways off. 6 marks c) Why are the signalling pathways required during embryonic development frequently implicated in cancer pathogenesis? 2 marks d) Describe two examples of how mis-regulated Sonic Hedgehog signalling leads to disease. 4 marks B2 a) What are protein chaperones and why are they important? 2 marks b) Give a brief summary of how Cryo Electron Microscopy (Cryo-EM) works, its advantages compared to X-Ray crystallography (for studying protein structure) and give one example where Cryo-EM is being used to understand disease. 8 marks c) Describe how proteins that are secreted from the cell are translated and released from the cell. 8 marks d) Why is ricin highly toxic, even in small doses? 2 marks Page 7 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 B3 a) Glycogen metabolism is often described as a good example of reciprocal regulation. What is meant in this case by the term ‘reciprocal regulation’? 2 marks b) Give one advantage and one disadvantage of storing energy in the form of glycogen. 2 marks c) Describe the steps involved in the regulation of: (i) glycogen synthesis (ii) glycogen catabolism Your answer should include all the steps from the binding of the appropriate hormone(s) to its receptor. 16 marks B4 a) Why are mitochondria more susceptible to damage than lysosomes? What are the consequences of damaged mitochondria to human health? 6 marks b) Compare the structure and function of mitochondria with the cell nucleus. 6 marks c) Describe the effects of factors that inhibit oxidative phosphorylation on cellular metabolism. Include specific examples in your answer. 8 marks Page 8 of 9 © Oxford Brookes University 04/05/21 Semester 2, 2020-2021 BIOS5003 B5 a) Describe the major metabolic changes that occur as the body goes from the well-fed state to the starved state. Include in your answer the role of hormones and how they co-ordinate this response at a molecular level. 14 marks b) Compare and contrast the benefits of 3 different ways Type I diabetics can monitor and control their blood plasma glucose. 6 marks B6 a) After a meal, how are amino acids that are not needed for protein synthesis metabolized? 10 marks b) Why is ammonia toxic, and how is it detoxified and excreted? 10 marks End of Examination Paper Page 9 of 9 © Oxford Brookes University 04/05/21