Q: Which equation is used to calculate the equilibrium potential for a single ion across a membrane?

$$E_x = 61 \log \frac{[\text{ion}]_o}{[\text{ion}]_i}$$

Question 1

Which of the following best describes the amphipathic nature of phospholipids in the plasma membrane?

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 2

Which equation is used to calculate the equilibrium potential for a single ion across a membrane?

Accepted Answer

$$E_x = 61 \log \frac{[	ext{ion}]_o}{[	ext{ion}]_i}$$

Question 3

A patient has a mutation that reduces the number of aquaporins in their cell membranes. Which process would be most directly affected?

Accepted Answer

Osmosis

Question 4

Which of the following is NOT a function of the plasma membrane?

Accepted Answer

Synthesizing proteins for the cell

Question 5

Which type of cell junction allows for the direct passage of ions and small molecules between adjacent cells, facilitating electrical communication in cardiac muscle?

Accepted Answer

Gap junctions

Question 6

According to Fick’s Law of Diffusion, which of the following changes would DECREASE the rate of diffusion across a membrane?

Accepted Answer

Increasing the molecular weight of the substance

Question 7

Which of the following best explains why the resting membrane potential of a neuron is closer to the equilibrium potential of potassium ($$E_{K^+}) $$than sodium ($$E_{Na^+}$$)?

Accepted Answer

The membrane is more permeable to potassium ions than sodium ions.

Question 8

A red blood cell is placed in a solution with higher osmolarity than its cytoplasm. What will happen to the cell?

Accepted Answer

It will shrink as water leaves the cell.

Question 9

Which of the following is a characteristic of active transport but NOT facilitated diffusion?

Accepted Answer

Movement of substances against their concentration gradient

Question 10

If the membrane potential ($$V_m) is -70 mV $$and the equilibrium potential for potassium ($$E_{K^+}) is -90 mV$$, what is the net force on potassium ions and in which direction will they move?

Accepted Answer

There is a net force of +20 mV, and potassium will move out of the cell.

Question 11

Which of the following best describes the role of cholesterol in the plasma membrane?

Accepted Answer

It increases membrane fluidity and stability by preventing fatty acid tails from packing together.

Question 12

Which of the following substances would most easily diffuse across the plasma membrane without assistance?

Accepted Answer

Oxygen (O$$_2)$$

Question 13

Which of the following is a function of glycoproteins and glycolipids on the outer surface of the plasma membrane?

Accepted Answer

Cell recognition and identification of ‘self’

Question 14

A cell uses a symport carrier to transport glucose into the cell along with sodium ions. Which of the following best describes this process?

Accepted Answer

Both glucose and sodium move in the same direction across the membrane.

Question 15

Which of the following best describes the Goldman equation?

Accepted Answer

It calculates the steady-state membrane potential considering multiple ions and their permeabilities.

Question 16

Which of the following is true regarding the sodium-potassium pump?

Accepted Answer

It moves 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell, using ATP.

Question 17

Which of the following scenarios would most likely increase the rate of simple diffusion of a small, nonpolar molecule across the plasma membrane?

Accepted Answer

Increasing the concentration gradient of the molecule across the membrane

Question 18

Which of the following best explains why large, polar molecules require facilitated diffusion to cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer prevents their passage.

Question 19

Which of the following is a real-life example of vesicular transport?

Accepted Answer

A white blood cell engulfing a bacterium via phagocytosis

Question 20

If a cell’s membrane potential ($$V_m) is -70 mV $$and the equilibrium potential for sodium ($$E_{Na^+}) is +60 mV$$, what is the net force on sodium ions and in which direction will they move?

Accepted Answer

There is a net force of -130 mV, and sodium will move into the cell.

Plasma Membrane Structure and Membrane Potential: Study Notes for Anatomy & Physiology

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