Untitled Notes

for question 305 to 327, answer the following subheadings:

question

answer

explain why or why not a?

explain why or why not b?

explain why or why not c?.

example:

question

325. The magnitude of the diffusion potential in an isolated system which starts with off-equilibrium:

a) remainsconstantintime;

b) changes in time, depending on the diffusion coefficient;

c) afterreachingamaximumitdecreasestozero.

answer

e.g. c) afterreachingamaximumitdecreasestozero.

explain why or why not a?

explain why or why not b?

explain why or why not c?.

use these questions and answer bank: 305- C

306- A

307- B

308- B

309_ A

310- A

311- B

312- A

313- A

314- B

315- A

316- B

317- A

318-C

319-B

320- B

321- B

322- A

323- B

324-C

325- C

326- B

327- B EXERCISE 9: DIFFUSION AND MEMBRANE POTENTIAL: EXPERIMENTAL METHODS

305. Which of the following formulas gives the closest approximation of the membrane potential at all times:

a) Henderson’s equation:

b) Nernst equation:

c) Goldman equation:

Where: u+ and u- are the mobilities of positive and negative ions,Cin/out or [ion] is the concentration of ions on both sides of the membrane, R is the universal gas constant, T is the absolute temperature in kelvin, F is the faraday’s constant, z is the valence of ion species (note that for Na+ and K+, z = 1; for Cl-, z = -1), Pion = permeability of the membrane for respective ion species.

306. Which of the following equations is used to calculate the diffusion potential for non-selective membrane?

a) Henderson equation:

b) Nernst equation:

c) Goldman equation:

307. Which of the following equations is used to calculate the diffusion potential for non-selective membrane?

a) Henderson equation:

b) Nernst equation:

c) Goldman equation:

308. How does the diffusion potential evolve with time?

a) thepotentialincreasesuntilthesystemreachesathermodynamicequilibrium,thenitassumesa constant value;

b) the potential increases until reaching a maximum value (stationary point) then it decreases back to zero;

c) the magnitude of the diffusion potential increases continuously with time.

309. What type of membrane allows for the generation of diffusion potential?

a) apermeablemembrane:allionscanpass;

b) non-permeable membrane: no ions can pass;

c) semipermeable membrane: only certain type of ions can pass.

310. What kind of state is established between the extra and the intra-cellular spaces during constant membrane potential?

a) astationarystate;

b) a thermodynamic equilibrium;

c) anon-equilibrium.

311. What conditions are necessary for the generation of diffusion potential?

a) a semipermeable membrane and two types of ion species;

b) a concentration gradient and ion species with different mobility;

c) a non-selective membrane and ions species with equal mobility.

312. Choose the correct statement:

a) after reaching a maximum, the diffusion potential decreases to zero;

b) after reaching a maximum, the membrane potential decreases to zero; c) the membrane potential never reaches a stationary point.

313. Choose the best definition for diffusion:

a) thedirectedmotionofthemoleculesofthesolutefromareawithhighsoluteconcentrationtoward area of low solute concentration;

b) the directed motion of the molecules of the solvent from area of low solute concentration toward area of high solute concentration;

c) thedirectedmotionofthemoleculesofthesolute,leadingtodecreaseofthetotalentropyofthe system.

314. Choose the correct statement regarding the process of diffusion.

a) therateofdiffusionisindependentofthetemperatureofthesystem;

b) the rate of diffusion depends on the concentration gradient;

c) therateofdiffusiondependsontheforthdigitofpi.

315. Which of the following conditions are necessary for the generation of membrane potential?

a) regulationofiontraffic,andthemaintenanceofionicconcentrationgradients;

b) maximisation of the entropy for the combined system of intra and extra-cellular spaces; c) activation of the Na+/K+ pump in non-electrogenic mode.

316. Choose the correct statement regarding the relative electric load between the extra and the intra- cellular environments during the resting state of the cell:

a) intracellular space is positive relative to the extracellular space;

b) extracellular space is positive relative to the intracellular space;

c) extracellularspaceiselectro-neutralrelativetotheintracellularspace.

317. Diffusion potential arises in a model system that satisfies the following conditions:

a) two electrolyte solutions of different initial concentrations (c1 ≠ c2) and different anion and cation mobility (u1 ≠ u2) are separated by a porous membrane;

b) two electrolyte solutions of the same initial concentrations (c1 = c2) and different anion and cation mobility (u1 ≠ u2) are separated by a porous membrane;

c) twoelectrolytesolutionsofdifferentinitialconcentrations(c1≠c2)andthesameanionandcation mobility (u1 = u2) are separated by a porous membrane.

318. Membrane potential is defined as:

a) the potential difference between two points on the external side of, and distant from the cellular membrane;

b) the potential difference between two points on the internal side of, and distant from the cellular membrane;

c) thepotentialdifferencebetweentwopointsonbothsides,andincloseproximity,ofthecellular membrane.

319. Choose the most precise definition of diffusion:

a) the process of migration of substance from area of higher concentration into area of lower concentration;

b) the spontaneous migration of substance from volume of high concentration into volume of low concentration due to the random thermal motion of the constituent particles;

c) theprocessofmasstransferdowntheconcentrationgradient.

320. Diffusion potential is measured with:

a) the “voltage clamp” method pioneered by Hodgkin and Huxley;

b) voltmeter placed between the two compartments with different concentrations;

c) scintillationcounterplacedatthemembrane,thatregisterstheiontraffic.

321. How do cells maintain a lower sodium concentration on the intracellular side of the membrane?

a) by balancing the concentration and electrical gradients of Na+ across the membrane;

b) with continuous use of energy of ATP;

c) bybalancingthediffusionandmembranepotentialsacrossthelipidbilayer.

322. Equilibrium potential across the membrane is achieved when:

a) forces due to concentration gradient = forces due to electric gradient;

b) osmotic pressure = hydrostatic pressure; c) membranepotential=diffusionpotential.

323. Membrane potential is measured in units of:

a) amperes

b) volts

c) coulombs

324. In a thermodynamic system under constant external conditions, the magnitude of the diffusion potential:

a) remainsconstantintime;

b) approaches the resting potential; c) approaches zero.

325. The magnitude of the diffusion potential in an isolated system which starts with off-equilibrium:

a) remainsconstantintime;

b) changes in time, depending on the diffusion coefficient; c) afterreachingamaximumitdecreasestozero.

326. In a thermodynamic system under constant external conditions, the diffusion potential:

a) approaches the membrane potential;

b) has a different maximum value depending on temperature;

c) has a maximum value that does not depend on the mobility ion species.

327. The magnitude of the membrane potential in a thermodynamic system under constant external conditions:

a) isamodelversionofthediffusionpotential;

b) has a different value under different temperature;

c) hasamaximumvaluedependingonthemobilityofpotential-generatingions.