School of Chemistry CHEM2523 Practice Quiz 1. Which of the following solutions would have the highest osmotic pressure? a. 0.1 M sucrose b. 0.05 M CaCl2 c. 0.1 M NaNO3 d. 0.075 M MgCl2 e. 0.2 M glucose General feedback: The answer is d. Osmotic pressure depends on the number of particles in solution, not on their charge. 2. How many hydrogen bonds does a water molecule form on average in liquid water: a. 4. b. 3.4. c. 3. d. 2. e. 2.4. General feedback: The answer is b. 3. What would the osmotic pressure of a 0.25 M solution of magnesium chloride at 37°C if it were an ideal solution? a. 5.2 x 106 N m-2 b. 2.6 x 106 N m-2 c. 1.9 x 106 N m-2 d. 1.3 x 106 N m-2 e. 3.9 x 103 N m-2 General feedback: The answer is c. The osmotic pressure is given by cRT. Remember that MgCl2 dissociates into three ions. Remember to use SI units, i.e. temperature in K, concentration in mol m-3. 4. Which of the following ions would you expect to have the lowest energy for transfer into the centre of a lipid bilayer? a. Na+ b. K+ c. Rb+ d. Li+ e. Cs+ General feedback: The answer is e. It has the lowest charge density. 5. Why can’t the patch clamp technique be used to measure the kinetics of single ion pumps? a. the molecules are too large b. the currents they produce are too small c. the currents they produce are too large d. the molecules are too small e. their kinetics are too fast General feedback: The answer is b. 6. In the cytoplasm of a cell the Na+ concentration is 10 mM; in the external solution it is 150 mM. The membrane potential, Vm = psiin – psiout = -60 mV. What is the free energy change (at 37°) for the transport of 1 mole of Na+ ions from the cytoplasm into the extracellular space? a. 146 J mol-1 b. 12800 J mol-1 c. -12800 J mol-1 d. 5930 J mol-1 e. -146 J mol-1 General feedback: The answer is b. The free energy change is given by the difference in the electrochemical potential of Na+ ions, i.e. extracellular space (final state) minus cytoplasm (initial state). Remember to use SI units, i.e. temperature in K and membrane potential in V. 7. Which of the following lipids is an ester? a. cholesterol. b. lauric acid. c. prostaglandin. d. beeswax. e. thromboxane. General feedback: The answer is d. 8. Which of the following is a complex lipid? a. myristic acid b. phosphatidylserine c. triglyceride d. olive oil e. carnauba wax General feedback: The answer is b. 9. Which of the following experimental techniques is used to measure the rate of rotational motion of molecules within a membrane surface? a. fluorescence recovery after photobleaching b. fluorescence correlation spectroscopy c. differential scanning calorimetry d. electron paramagnetic resonance spectroscopy e. time-resolved fluorescence anisotropy or polarisation General feedback: The answer is e. 10. Which of the following proteins requires ATP as a source of energy? a. Na+-glucose cotransporter b. ATP synthase c. Cytochrome c oxidase d. Na+ channel e. lipid flippase General feedback: The answer is e. 11. Which of these intermolecular forces is broken during the main phase transition of a lipid membrane? a. hydrogen bonding b. van der Waals forces c. hydrophobic interactions d. pi-pi stacking e. salt bridge General feedback: The answer is b. 12. Which of the following has the lowest permeability towards a lipid membrane? a. water b. tetraphenylborate c. chloride d. a sodium ion e. glucose General feedback: The answer is d. 13. For the distribution of an ion across a membrane to be in equilibrium which of the following must be true? a. the electrochemical potential of the ion must be the same on each side of the membrane b. the chemical potential of the ion must be the same on each side of the membrane c. concentration of the ion must be the same on each side of the membrane d. there must be no electrical potential difference across the membrane e. the membrane must be impermeable to the ion. General feedback: The answer is d. 14. Which of the following is not derived from cholesterol? a. bile salts b. prostaglandin c. testosterone d. progesterone e. cortisone General feedback: The answer is b. 15. Which of the following is measured in differential scanning calorimetry? a. temperature b. changes in weight c. heat capacity d. entropy e. free energy General feedback: The answer is c.
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