BIO250 April 2007 Final Exam.pdf

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University of Toronto St. George

UNIVERSITY OF TORONTO Faculty of Arts and Science April Exam Tuesday, April 24, 2007 BIO250Y1Y From 2-5 pm DURATION: three (3) hours (180 minutes) No Examination Aids Allowed Number of pages: 25 (not including this one) Number of questions: 75 multiple choice This examination is worth 30% of your final mark. INSTRUCTIONS: Please read carefully! 1. Questions 1- 50 are based on lecture materia(Sections III and IV), questions 51 75 are based on labs 7 - 12. You are to choose the BEST answer; there is ONE and only one correct answer per question (multiple answers for a qu estion will be marked wrong). There is no additional penalty for incorrect answers, sodo NOT leave any questions unanswered (blank) on your answer sheet. Write your name on your exam question paper. 2. Green Computer Answer Sheet: SCANTRON(See sample on the back of this page) Transfer your answers to the computer scan tron answer sheet using a soft lead pencil darken inside one box ONLY as mult iple answers will be marked wrong . Erase all corrections completely. ONLY your answer sheet will be marked. On the left side of your computer answer sheet: a) Print your last name in the boxes provided, and darken the appropriate letters in each column. Print your first name initial(s) in the far right columns and darken the appropriate letters. b) Print your student number and carefully darken the appropriate numbers. Do not leave this section blank. c) Print the exam version in "CODE" and darken in the appropriate numbers. The exam version is at the bottom of every page of this exam. ------------------------------ Hand in BOTH your COMPUTER ANSWER SHEET and your Exam PAPER EXAM VERSION 99 Version 99 2 Continued 1. Which of the following statements concerning the composition of cell membranes is CORRECT? a) Plasma membranes contain lipid rafts that are rich in phospho lipids with short fatty acid chains. b) Phosphatidylserine is found in high concentra tions in the outer l eaflet of the plasma membrane. c) Phospholipids in the plasma membrane can be covalently modified during cell signalling. d) The percentage of specific phospholipids is the same for all cellular membranes. e) Glycolipids are found in higher amounts in the cytosolic leaflet of the plasma membrane. 2. You would like to determine how a specific memb rane protein is anchored to the plasma membrane. You express a fusion protein in cells in which the protein of interest is fused to GFP. As expected, most of the fluorescence is localized to the plasma membrane. You then add phospholipase C to the medium bathing th e cells. The fluorescence disappears from the membrane. What can you conclude? a) The protein is anchored via its transmembrane region, which is composed of amino acids. b) The protein is a peripheral protein. c) The protein is anchored via a prenyl anchor. d) The protein is anchored via a glycosylphosphatidylinositol anchor. e) The protein is anchored via a fatty acid chain. + + 3. Which of the following is a step in the model of Na /K pump action? a) The pump is not phosphorylated, instead the hydrolysis of ATP simply provides energy. b) In one conformation, 3 Na ions bind to high affinity sites on the extracellular face. + c) Na ions dissociate from low affinity sites on the cytosolic face. + + d) Na ions and K ions are transported through the pump simultaneously. e) In one conformation, 2 K ions bind to high affinity sites on the exoplasmic face. 4. Glucose uniporters are a family of proteins th at transport glucose. Which of the following concerning these uniporters is CORRECT? a) GLUT-2 has a high K inmicating that it has a high affinity for glucose. b) GLUT-4 is localized to plasma membranes of fat and muscle cells when insulin levels are low. c) GLUT-1 supplies glucose to most cells of the body independent of insulin concentrations. d) GLUT-1 has a low K m indicating that it has a low affinity for glucose. e) At low glucose concentrations, the rate of tr ansport through GLUT-2 is faster than the rate of transport through GLUT-1. Version99 3 Continued 5. Which of the following statements concerning ATP synthase and the synthesis of ATP is NOT correct? a) ATP synthase contains a transmembrane F regio0 through which protons travel. b) The energy supplied as protons move down their electrochemical gradient is converted to mechanical energy. c) ATP synthases are of ancient origin and occur in plants, animals and bacteria. d) ADP and Pi bind to subunits in the F 1region where they are converted to ATP. e) V-type ATPases pump protons into the in termembrane space of mitochondria to generate a gradient that provides the energy for ATP synthesis. 6. Which of the following contributes most to the generation of the resting membrane potential in animal cells? a) Active transport of K into the cell by the Na /K ATP pump. + + b) Passive transport of K out of cells via K leak channels. + c) P-type ATPases that actively pump H out of cells. + + + d) Active transport of Na into the cells by the Na /K ATP pump. e) Passive transport of K out of cells via voltage-gated K channels. 7. Which of the following is (are) CORRECT concerning characteristics of antiporters? a) They transport two solutes in the same direction across the membrane. b) They transport one solute against and one solute with an electrochemical gradient. c) They transport one solute in one direction and another solute in the opposite direction across the membrane. d) both a and b. e) both b and c. 8. Which of the following statements concerning plant vacuoles is CORRECT? a) Cl -moves down its concentration gradient and into vacuoles via channel proteins. b) V-type ATPases pump protons out of vacuoles and into the cytoplasm. + + + c) The energy required to transport Na into vacuoles via Na /H antiporters is supplied by a proton motive force. d) The inside of the membrane of the vacuole is negatively charged in comparison with the cytosolic side of the membrane. e) P-type ATPases pump Ca 2+against its electrochemical gradient into the lumen of the vacuole. Version99 4 Continued
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