Which of the following statements best describes the features of voltage-gated K+ channels? They consist of 4 subunits, are activated at the same time as voltage-gated Na+ channels, but do not inactivate. They consist of 4 subunits, are activated by depolarisation and close slowly during the refractory period. They have 24 membrane spanning alpha helices, 4 of which have positively charged amino acids which promote a conformational change in the channel following depolarisation. They consist of 4 subunits and are open at rest which causes the resting membrane potential to be close to the K+ equilibrium potential.

Which of the following statements best describes the features of voltage-gated K+ channels? They consist of 4 subunits, are activated at the same time as voltage-gated Na+ channels, but do not inactivate. They consist of 4 subunits, are activated by depolarisation and close slowly during the refractory period. They have 24 membrane spanning alpha helices, 4 of which have positively charged amino acids which promote a conformational change in the channel following depolarisation. They consist of 4 subunits and are open at rest which causes the resting membrane potential to be close to the K+ equilibrium potential.

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter4: Principles Of Neural And Hormonal Communication

Section: Chapter Questions

Problem 17RE

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One of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?
Conformational changes in channel proteins brought about by voltage changes are responsible for opening and closing Na+ and K+ gates during the generation of an action potential. (True or false?)
Assume that a membrane permeable to Na+ but not to Cl- separates two solutions. The concentration of sodium chloride on side 1 is higher than on side 2. Which of the following ionic movements would occur? a. Na+ would move until its concentration gradient is dissipated (until the concentration of Na+ on side 2 is the same as the concentration of Na+ on side 1). b. Cl- would move down its concentration gradient from side 1 to side 2. c. A membrane potential, negative on side 1, would develop. d. A membrane potential, positive on side 1, would develop. e. None of the preceding is correct.
Which of the following statements about voltage gated channels is true? Voltage-gated sodium channels open at a higher (more positive) membrane potential than do potassium-gated channels Voltage-gated sodium channels open at a lower (more negative) membrane potential than do potassium-gated channels Sodium- and postassium-gated channels open at about the same membrane potential, but they have different effects because there are different numbers of the two kinds of channels in neuron cell membranes
Which of the following is the correct statement regarding ion channels? Physical deformation of the membrane cannot open ion channels Ligand-gating means that an ion binds to the channel, which stimulates its opening. If the channel pore was the right size, Na and K could both pass through because they have the same charge A voltage gated Na channel can open to allow Na movement against its electrochemical gradient
You attempt to generate an IV plot for GABA channels in cultured neurons. You apply pentobarbital and perform voltage steps but see no current at any voltage. Which of the following would explain your findings? Concentration of pentobarbital is too low GABA is not present in your solutions Cl- concentration is equal on both sides of the membrane None of the above
Which of the following ion channels are always sensitive to small changes in electric charge? stress-activated channels ligand-gated channels with extracellular ligands voltage-gated channels ligand-gated channels with intracellular ligands all of the above
Which of the following ion channels are always electrosensitive? stress-activated channels ligand-gated channels with extracellular ligands voltage-gated channels ligand-gated channels with intracellular ligands all of the above
Separately, draw a table using arrows to depict the appropriate magnitude and direction of the forces and ion fluxes at different membrane potentials for a ligand-gated channel that is equally permeable to both ion X+ and ion Y+. The equilibrium potential for ion X+ is -60 mV, and the equilibrium potential for ion Y+ is -20 mV. Which item best represents the forces and fluxes for a membrane potential of -20 mV?
Separately, draw a table using arrows to depict the appropriate magnitude and direction of the forces and ion fluxes at different membrane potentials for a ligand-gated channel that is equally permeable to both ion X+ and ion Y+. The equilibrium potential for ion X+ is -60 mV, and the equilibrium potential for ion Y+ is -20 mV. Which item best represents the forces and fluxes for a membrane potential of -60 mV? Pick one of the four tables in the included image please for your answer.
Neurons have a resting membrane potential of ___________________. varying votage as type and composition of channels can differ between neurons. theoretically the same votage because the ionic concentration is the same extracellularly and intracellularly for all neurons. equal to the equillibrium potential for potassium. directly opposing the equillibrium potential for sodium.
What is the free energy change for the transport of calcium ions (Ca++) across a membrane from a region (left) where the concentration is 50 micromolar to a region (right) where the concentration is 50 micromolar? A membrane potential of 60 mV exists across the membrane where the right side is more negative than the left side. The temperature is 25 C.

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		They consist of 4 subunits, are activated at the same time as voltage-gated Na⁺ channels, but do not inactivate.
		They consist of 4 subunits, are activated by depolarisation and close slowly during the refractory period.
		They have 24 membrane spanning alpha helices, 4 of which have positively charged amino acids which promote a conformational change in the channel following depolarisation.
		They consist of 4 subunits and are open at rest which causes the resting membrane potential to be close to the K⁺ equilibrium potential.