Mathias Exam Questions
25. A kidney cell receives a signal (ADH) to insert more aquaporins into its plasma membrane. The apical side of the cell faces a solution containing 145 mM NaCl, 4 mM KCl and 2 mM CaCl2 (we can assume the osmotic coefficients are unity). The intracellular solution has an osmolarity of 300 mOsm. Immediately following insertion of the aquaporin, water flow across the apical membrane will:
a. increase into the cell.
b. decrease into the cell.
c. not change.
d. increase out of the cell.
e. decrease out of the cell.
26. A red blood cell initially contains 200 mOsm of permeant solute and 100 mOsm of impermeant solute. After being placed in a large bath containing 300 mOsm of permeant solute, you would expect:
a. its volume will increase to 3/2 of its initial volume.
b. its volume will decrease to 2/3 of its initial volume.
c. its volume will decrease to 1/3 of its initial volume.
d. its volume will increase until it ruptures.
e. its volume will not change.
27. In all animal cells the energy stored in ATP is directly used to:
a. transport Na+ out.
b. transport K+ out.
c. transport Ca2+ in.
d. transport H+ in.
e. transport glucose in.
28. Small ions do not enter cells by:
a. pinocytosis.
b. membrane channels.
c. primary active transport.
d. secondary active transport.
e. diffusion through the lipid barrier.
29. The membrane conductance does not directly depend on:
a. the open probability of membrane channels.
b. the Nernst potential for each ion.
c. the number of channels in the membrane.
d. random gating of membrane channels.
e. the single channel conductance of each contributing channel.
30. In a cell at rest, there are 108 K+ channels in the plasma membrane, each with an open probability of 0.1 and a single channel conductance of 10 x 10-12 S. The total K+ conductance of the membrane due to these channels is:
a. 10-3 S.
b. 10-4 S.
c. 10-5 S.
d. 1019 S.
e. 1021 S.
31. Given intracellular Na+ is 10 mM; extracellular Na+ is 100 mM; intracellular K+ is 100 mM; extracellular K+ is 10 mM; gNa = 0.01 mS/cm2; gK = 0.11 mS/cm2; and Cl- is in equilibrium, what is the Cl- Nernst potential?
a. ECl = -50 mV
b. ECl = -60 mV
c. ECl = +60 mV
d. ECl = 0 mV
e. ECl cannot be determined
32. Which of the following is never true of sheets of epithelial cells?
a. The cells are connected by gap junctions.
b. Active and passive membrane transport are on opposite sides.
c. They line body cavities.
d. They transport both salt and water.
e. They contract in response to a Ca2+ action potential.
33. An action potential is recorded and found to have a duration of 300 ms. The recording was most likely made from:
a. a nerve axon.
b. a motor neuron.
c. a skeletal muscle fiber.
d. a cardiac muscle fiber.
e. a smooth muscle cell.
34. A genetically altered squid has no voltage dependent K+ channels in its nerves. The effect on action potentials is to:
a. There is no effect.
b. decrease propagation velocity.
c. increase (more positive) threshold.
d. increase the relative refractory period.
e. decrease the relative refractory period.
35. Which of the following gating processes has the most rapid kinetics?
a. Na+ channel inactivation
b. Na+ channel activation
c. K+ channel activation
d. Ca2+ Channel activation
e. Ca2+ channel inactivation
36. A smooth muscle action potential is generated by Ca2+ channels and K+ channels. Given ECa = +90 mV, EK = -90 mM and peak action potential voltage is +30 mV, what is the ration of GCa:GK at the peak?
a. 1:1
b. 2:1
c. 4:1
d. 6:1
e. 8:1
37. Which of the following would result from a demyelinating disease?
a. Increased propagation velocity
b. Decreased conductance per length of axon
c. Decreased capacitance per length of axon
d. Decreased safety factor
e. Increased frequency of action potentials
38. Which of the following would decrease propagation velocity of a nerve action potential?
a. Myelination of the axon
b. Increased diameter of the axon
c. Increased capacitance per length of axon
d. Decreased capacitance per length of axon
e. Increased length constant of the axon
39. One action potential in a motor neuron causes a train of action potentials in the skeletal muscle fibers of its motor unit. The defect could be:
a. too little ACh per quanta.
b. too few quanta released per nerve action potential.
c. too few ACh receptors.
d. too little ACh esterase.
e. too few Ca2+ channels in the presynaptic terminal.
40. At the neuromuscular junction, the miniature end plate potential (MEPP) is due to:
a. the release of one molecule of ACh.
b. the activation of one ACh receptor.
c. one presynaptic action potential.
d. the release of one quanta of ACh.
e. one muscle action potential.
41. An unknown neurotransmitter causes a postsynaptic current that reverses from inward to outward at a membrane voltage of 0 mV. Which of the following is true?
a. The postsynaptic receptor is a K+ channel.
b. The postsynaptic effect is excitatory.
c. The postsynaptic effect is inhibitory.
d. The postsynaptic receptor is a Cl- channel.
e. The neurotransmitter is GABA.
42. Which of the following is not true of a slow synapse?
a. The postsynaptic receptor is an ion channel.
b. The postsynaptic receptor is coupled to a G protein.
c. The postsynaptic response persists after transmitter release ceases.
d. The postsynaptic response may be the opening of an ion channel.
e. The neurotransmitter binds to a postsynaptic receptor.