NPB 100 Chapter 4 Test Bank

Based on the observations made by Hodgkin and Huxley, one can expect ion channels to

a. allow ions to move across the membrane quickly.

b. work with the electrochemical gradients to pass ions.

c. exist in distinct variants, allowing different types of ions to pass.

d. respond to changes in the membrane potential.

e. All of the above

e. All of the above

Ion channels that are involved in generation of action potentials open or close in response to

a. voltage.

b. neurotransmitters.

c. second messengers.

d. mechanical stimulation.

e. temperature.

a. voltage.

Which technique is illustrated in the figure, and what can it be used to measure?

a. Whole-cell patch clamp; measures potentials from the entire cell

b. Whole-cell patch clamp; measures the current that flows through a single ion channel

c. Cell-attached patch clamp; measures potentials from the entire cell

d. Cell-attached patch clamp; measures the current that flows through a single ion channel

e. Outside-out patch clamp; measures the current that flows through a single ion channel

d. Cell-attached patch clamp; measures the current that flows through a single ion channel

In the phase labeled B, the voltage-gated sodium channels are ________ and the voltage-gated potassium channels are ________.

a. open; closed

b. closed; open

c. open; open

d. inactivated; open

e. closed; inactivated

a. open; closed

In the phase labeled D, the voltage-gated sodium channels are ________ and the voltage-gated potassium channels are ________.

a. open; closed

b. closed; open

c. open; open

d. inactivated; open

e. closed; inactivated

d. inactivated; open

The proteins that establish ionic gradients are called

a. passive transporters.

b. active transporters.

c. voltage-gated ion channels.

d. ligand-gated ion channels.

e. permeability transition pores.

b. active transporters.

There are nearly 100 genes for K+ channels. What value might there be in such variation?

The value of a large number of genes, which fall into several distinct groups of channel proteins, is that several different K + channel proteins can be produced from them, each different from one another in function, permitting variation in cell function, such as the different signaling properties found among neurons.

What is patch clamping? Explain how it can be used to show that properties of voltage-sensitive Na+ and K+ channels are responsible for the action potential.

Patch clamping is a technique in which a recording pipet is used to grip a cell membrane and record the electrical potential or flow of ions through one ion channel. The patch clamp method allows experimental control of the membrane potential, and it can be used to characterize the voltage dependence of membrane currents. It allows measuring minute electrical currents such as those originating from a single ion channel

What is the net charge transported by one cycle of the Na+/ K+ ATPase pump?

a. One positive charge leaves the cell

b. Two positive charges leave the cell

c. Three positive charges leave the cell

d. One positive charge enters the cell

e. There is no net change in charge

a. One positive charge leaves the cell

Which statement is a common, defining feature of membrane-bound active ion transporters?

a. All are electrogenic.

b. All transport two or more different ions.

c. All catalyze the conversion of ATP to ADP.

d. All are able to move at least one ion against its concentration gradient.

e. All move sodium across the membrane.

d. All are able to move at least one ion against its concentration gradient.

Which structural features of K+ channels account for: a) ion selectivity, b) voltage sensitivity, and c) ion conductance?

a) Selectivity filter: pore loops create a pore too small for larger ions but too large for smaller ions to be stabilized.

b) Voltage sensor

c) Pore

Compare the responses of voltage-gated Na+ and K+ channels to depolarization.

Both types of channels open in response to depolarization; however, depolarization inactivates Na+ channel for a period of time. In contrast, K+ channels are not inactivated.