UNIVERSITY OF YORK. BA, BSc, and MSc Degree Examinations Department : BIOLOGY. Title of Exam: Membrane transport. Time Allowed: 2 hours

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1 Examination Candidate Number: Desk Number: UNIVERSITY OF YORK BA, BSc, and MSc Degree Examinations Department : BIOLOGY Title of Exam: Membrane transport Time Allowed: 2 hours Marking Scheme: Total marks available for this paper: 100 Sec on A: Short Answer / Problem / Experimental Design ques ons (50 marks) Sec on B: Essay ques on (marked out of 100, weighted 50 marks) The marks available for each ques on are indicated on the paper Instructions: Sec on A: Answer all ques ons in the spaces provided on the examina on paper Sec on B: Answer either ques on A or ques on B. Write your answer on the separate paper provided and a ach it to the back of the ques on paper using the treasury tag provided. Materials supplied: For marker use only: CALCULATOR For office use only: Module total as % DO NOT WRITE ON THIS BOOKLET BEFORE THE EXAM BEGINS DO NOT TURN OVER THIS PAGE UNTIL INSTRUCTED TO DO SO BY AN INVIGILATOR page 1 of 9

2 SECTION A: Short Answer / Problem / Experimental Design questions Answer all questions in the spaces provided Mark total for this section: Using an ion selective electrode you measure 0.1 mm Mg in the plasma of a patient and around 1 mm Mg inside red blood cells. You know in a healthy patient the Mg Nernst potential 'E Mg ' (or equilibrium potential) should be ~-60 mv. To what concentration does the red blood cell Mg concentration need to change to reach ~-60 mv? E=RT/zF ln [Mg 2+ ] out /[Mg 2+ ] in (2 marks) 2. Explain why the catalytic mechanism of the Lac permease and other carriers is referred to as the 'rocker switch' model and describe its salient features. (4 marks) page 2 of 9

3 3. You are heterologously expressing KCNQ4 in HEK cells. A whole cell recording shows only a small outward current and you suspect you may be working with a defective KCNQ4 protein. Describe the patch clamp experiments you would run to ensure that your current is generated by KCNQ4. If you find that this is the case, how would you determine whether the protein is wildtype, a gating mutant or a pore mutant. (7 marks) 4. A patient presents with long QT syndrome. Discuss how this affliction is caused and whether treatment with nicorandil would be a viable treatment. (4 marks) page 3 of 9

4 5. a) In what organ/tissue does uric acid transport occur and what are the main diseases that result from faulty uric acid transport? (3 marks) b) Describe the role of URAT1 in gout and discuss a research strategy based on a GWAS (genome wide association study), to identify polymorphisms in this transporter URAT1 and how you would use this to devise a treatment. (7 marks) page 4 of 9

5 6. Single-molecule tracking of a cystic fibrosis transmembrane conductance regulator (CFTR) channel labelled with an extracellular tag yielded mean-square displacement (MSD) data which was dependent on its specific location in the plasma membrane. a) Explain how the above MSD data can be used to quantify the diffusive properties of the CFTR channel in membrane regions 1 and 2, and then compare the diffusive properties observed in each region. (4 marks) b) Describe how these MSD data inform about the long-range mobility of the CFTR channel in membrane regions 1 and 2 of this cell type. (3 marks) page 5 of 9

6 c) What determines the time-resolution in these MSD experiments? (1 mark) d) What are the benefits of using an extracellular tag in these single-particle tracking experiments compared with a GFP fusion to the CFTR channel? (2 marks) e) Adding 10 histidine residues to the C-terminus of the CFTR channel increased the long-range mobility of the channel in the plasma membrane. How might the observed MSD data for region 2 be explained based on these results? (4 marks) the space above this line should be sufficient for your answer page 6 of 9

7 7. Below is the Na + current-voltage relationship of a hippocampal pyramidal neuron from a mouse measured using whole-cell patch clamp recording. The internal solution contained 150 mm KCl and 5 mm NaCl. The external solution contained 5 mm KCl and 150 mm NaCl. The external solution also contained 30 mm TEA-Cl and 0.3 mm CdCl 2 to block K + and Ca 2+ currents, respectively. The whole-cell capacitance was measured to be 40 pf. a) What is the peak current density? (1 mark) b) What is the reversal potential? (1 mark) c) Why is the current non-linear between -50 mv and -10 mv? (2 marks) d) Explain what would happen to the reversal potential if TEA-Cl was removed from the external solution. (2 marks) page 7 of 9

8 e) Design an experiment you could perform to test the involvement of β1 subunits in regulating this Na + current and describe what you would expect to find. (3 marks) the space above this line should be sufficient for your answer page 8 of 9

9 SECTION B: Essay question Answer one question on the separate paper provided Remember to write your candidate number at the top of the page and indicate whether you have answered question A or B Mark total for this section: 50 EITHER A) Design and discuss an experimental approach that would allow you to determine the Michaelis-Menten parameters of an acetylcholine accumulating transporter, located in synaptic vesicles, and how the transporter is energised. OR B) Using specific examples, discuss how preclinical in vitro and i n vivo studies have contributed to our understanding of the role of Nav1.1 channels in Dravet syndrome. page 9 of 9