Q: Which equation correctly represents the Nernst equation for calculating the equilibrium potential ($$E) of an $$ion across a membrane?

$$E = \frac{RT}{zF} \ln \left( \frac{[\text{ion}]_{\text{outside}}}{[\text{ion}]_{\text{inside}}} \right)$$

Question 1

Which of the following best describes the difference between passive and active transport across cell membranes?

Accepted Answer

Passive transport moves molecules down their concentration gradient without energy input, while active transport moves molecules against their gradient using energy.

Question 2

Which equation correctly represents the Nernst equation for calculating the equilibrium potential ($$E) of an $$ion across a membrane?

Accepted Answer

$$E = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 3

A neuron is at rest. Which ion has the highest concentration inside the cell compared to outside?

Accepted Answer

K$$^+$$

Question 4

Which of the following statements about ion channels is TRUE?

Accepted Answer

Ion channels are selective for specific ions and can be gated by stimuli such as voltage or ligands.

Question 5

During an action potential, which event occurs first?

Accepted Answer

Voltage-gated Na$$^+$$ channels open, allowing Na$$^+ to $$enter the cell.

Question 6

Which process is responsible for restoring the resting ion concentrations after an action potential?

Accepted Answer

Na$$^+/K$^+$$ ATPase pump

Question 7

A mutation causes voltage-gated Na$$^+$$ channels to remain inactivated. What is the most likely effect on neuronal signaling?

Accepted Answer

Action potentials will fail to propagate along the axon.

Question 8

Which of the following best explains why K$$^+$$ leak channels are important for the resting membrane potential?

Accepted Answer

They allow K$$^+ to $$move out of the cell, balancing the negative charge from organic anions inside.

Question 9

Which of the following is a real-life example of a ligand-gated ion channel?

Accepted Answer

The acetylcholine receptor at the neuromuscular junction

Question 10

Which step in synaptic transmission directly depends on the influx of Ca$$^{2+}$$ ions?

Accepted Answer

Release of neurotransmitter from synaptic vesicles

Question 11

A patient is exposed to a toxin that blocks acetylcholine receptors at the neuromuscular junction. What is the most likely physiological effect?

Accepted Answer

Muscle contraction will be inhibited.

Question 12

Which of the following is TRUE about the propagation of an action potential along an axon?

Accepted Answer

It is actively renewed by sequential opening of voltage-gated Na$$^+$$ channels.

Question 13

Which formula best describes the relationship between membrane potential ($$V_m$$), ion concentrations, and permeability according to the Goldman-Hodgkin-Katz equation?

Accepted Answer

$$V_m = \frac{RT}{F} \ln \left( \frac{P_{K^+}[K^+]_{	ext{outside}} + P_{Na^+}[Na^+]_{	ext{outside}} + P_{Cl^-}[Cl^-]_{	ext{inside}}}{P_{K^+}[K^+]_{	ext{inside}} + P_{Na^+}[Na^+]_{	ext{inside}} + P_{Cl^-}[Cl^-]_{	ext{outside}}} ight)$$

Question 14

Which of the following would most likely result from a defect in the Na$$^+/K$^+$$ pump?

Accepted Answer

The resting membrane potential would be lost due to disrupted ion gradients.

Question 15

Which of the following is NOT a characteristic of facilitated diffusion?

Accepted Answer

It requires direct energy input from ATP hydrolysis.

Question 16

A researcher uses patch-clamp recording to study ion channel activity. What is being measured?

Accepted Answer

The electrical current flowing through individual ion channels

Question 17

Which of the following best describes the role of voltage-gated Ca$$^{2+}$$ channels in synaptic transmission?

Accepted Answer

They trigger the fusion of synaptic vesicles with the presynaptic membrane.

Question 18

Which of the following scenarios would most likely result in an inhibitory postsynaptic potential (IPSP)?

Accepted Answer

Opening of ligand-gated Cl$$^-$$ channels

Question 19

Which of the following is TRUE regarding the selectivity of ion channels?

Accepted Answer

Selectivity is determined by the size and charge of the channel's pore lining.

Transport Across Cell Membranes and Membrane Potential

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