Solved by a verified expert:Name______________________________TA _____________________________NPB 104L Quiz 5Multiple ChoiceIdentify the letter of the choice that best completes the statement or answers the question.(1 pt each)________1. You are studying the regulation of a proton transport molecule in the outer mitochondrial membrane. Further,you predict that a mystery compound, Y, leads to an increase in the number of proton transport moleculesembedded in this membrane. In order to set up an experiment to test this hypothesis what should you varyand what should you measure?a. vary sodium in the presence and absence of Y, measure transport activityb. vary H+ in the presence and absence of Y, measure transport activityc. vary Y in the presence and absence of H+, measure the number of transportersd. vary the number of transporters, measure proton flux across the membranee. vary transport activity in the presence and absence of Y, measure H+ concentration in theinter-membrane space2. Which of the following is an invalid prediction based upon our model of oxidative phosphorylation?a. A complete block of the electron transport chain at complex III will stop oxygenconsumption.b. Insertion of a gradient driven proton carrier in the outer mitochondrial membrane wouldlead to increased oxygen consumption.c. Excess inorganic phosphate in the matrix will cause a leak of inorganic phosphate into theinter membrane space where it will inhibit binding of protons to the ATP synthasemolecule.d. Artificially increasing the H+ concentration in the inter membrane space should drive moreATP production.Short Answer3. You are asked to investigate the affect of ADH on frog skin and are given the following information (seetable). You then proceed to put a piece of frog skin in an Ussing chamber and fill both sides with 100%Ringers solution. Suspecting that ADH works by increasing the permeability of the apical membrane to Na+you want to see if adding ADH will drive the activity of the pump by increasing availability of substrate. Youprepare to add a physiological concentration of ADH to the chamber facing the basolateral side of theepithelium and set out to measure pump activity. You intend to compare the activity of the pump in thepresence and absence of ADH. What is wrong with the experiment as you’ve set it up? What would you dodifferently? (2 pts)%Na+ (apical)25102050100Na+/K+ pump Velocity20 2.135 1.348 0.852 3.058 2.559 1.51 Name______________________________TA _____________________________4. We know that the production of ATP must be varied in order to match demand and we saw that the P/O ratiosrecorded in lab were consistently lower than the classic value calculated for succinate (2.5). List threedifferent sites in the mitochondrion where cellular regulation could affect the P/O ratio and state how eacheffect would be mediated (these are regulatory mechanisms used by the cell – not artificial interventions likeadding a manufactured uncoupler!). Describe one biologically beneficial reason why P/O ratio’s might belower than 2.5. (2 pts)1.2.3.Why?Long Answer5. You run the following two experiments:1) You vary the concentration of substance X in the solution bathing your test cells and measure the activityof the Na+/K+ ATPase. You get the following data:[X](mM)1 x 10-33 x 10-310 x 10-330 x 10-3100 x 10-3Na+/K+ ATPaseActivity11.2 +/- 0.0317.7 +/- 0.0721.2 +/- 0.0525.3 +/- 0.0329.1 +/- 0.062) You repeat exactly the same experiment with one difference: this experiment is run in the presence ofFCCP and get the following data:With FCCP[X](mM)1 x 10-33 x 10-310 x 10-330 x 10-3100 x 10-3Na+/K+ ATPaseActivity10.2 +/- 0.0311.7 +/- 0.0712.2 +/- 0.0513.3 +/- 0.0313.6 +/- 0.062 Name______________________________TA _____________________________A) What is the important consequence of exposing cells to FCCP as it pertains to Na+/K+ ATPaseactivity? (1 pt)B) State a hypothesis for which the first experiment would be run as a test of that hypothesis. (1 pt)C) What do the results of the second experiment suggest to us about the mechanism of X’s action?(1 pt)6. In class we discussed current-voltage relations for sodium and potassium and I plotted the following data:A) In order to describe ionic current we rearranged Ohm’s Law to get: INa = gNa(Vm-ENa). Wereferred to the term inside the parentheses as the “driving force”. What two forces are accounted forby this term and how is each accounted for? (1 pt)B) Why is the slope of the sodium current line less steep than that of the potassium current line? (1pt)3 Name______________________________TA _____________________________C) Identify Point “A” on the graph. How is sodium current different to the left versus the right ofthis point? Why? (1 pt)D) Which is greater at the normal resting membrane potential, sodium current or potassium current(put dots on the graph to indicate where you’re getting your answer)? Why is this so? How do themagnitudes of these two currents relate to the stoichiometry of the sodium/potassium pump? (3 pts)4
Recent Comments