Question 1

Which of the following best describes the main function of the plasma membrane in a typical animal cell?

Accepted Answer

It separates the intracellular environment from the extracellular environment, controlling the entry and exit of substances.

Question 2

According to the Fluid Mosaic Model, which component is primarily responsible for the membrane's fluidity and stability?

Accepted Answer

Cholesterol

Question 3

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

Accepted Answer

A small nonpolar molecule

Question 4

Which type of cell junction allows for the direct passage of ions and small molecules between adjacent cells, facilitating electrical and metabolic coupling?

Accepted Answer

Gap junctions

Question 5

A patient is given an intravenous solution with a higher osmolarity than their blood plasma. What will happen to their red blood cells?

Accepted Answer

Water will leave the cells, causing them to shrink.

Question 6

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

Accepted Answer

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

Question 7

If the resting membrane potential ($$V_m) is -70 mV $$and the equilibrium potential for potassium ($$E_K) is -90 mV$$, what is the net force acting on potassium ions?

Accepted Answer

$$+20 mV$$, driving K^+ out of the cell

Question 8

Which of the following best explains why the inside of a resting cell membrane is negative relative to the outside?

Accepted Answer

Potassium ions leak out of the cell more easily than sodium ions enter.

Question 9

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

Accepted Answer

Storing genetic information

Question 10

A cell is placed in a solution and water moves into the cell. Which of the following best describes the solution?

Accepted Answer

Hypotonic

Question 11

Which of the following best describes the role of the Na+/K+ pump in maintaining the resting membrane potential?

Accepted Answer

It actively transports Na+ out of the cell and K+ into the cell, maintaining concentration gradients.

Question 12

Which of the following is true regarding facilitated diffusion?

Accepted Answer

It requires a membrane protein and moves substances down their concentration gradient.

Question 13

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

Accepted Answer

Decreasing the surface area ($$A)$$

Question 14

Which of the following best describes the function of carbohydrates on the outer surface of the plasma membrane?

Accepted Answer

They serve as recognition sites for cell-cell interactions.

Question 15

Which of the following transport mechanisms requires energy input and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 16

A mutation causes a cell to lack aquaporins. Which process would be most directly affected?

Accepted Answer

Osmosis

Question 17

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 18

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

Accepted Answer

A white blood cell engulfing a bacterium by phagocytosis

Question 19

Which of the following statements about membrane permeability is correct?

Accepted Answer

The plasma membrane is more permeable to K+ than to Na+ at rest.

Question 20

If the permeability of the membrane to sodium increases dramatically, what would happen to the membrane potential?

Accepted Answer

It would move closer to the equilibrium potential for sodium ($$E_{Na}).$$

The Plasma Membrane and Membrane Potential: Structure, Function, and Transport

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