Question 1

Which of the following best describes the main function of the sodium-potassium pump in maintaining the resting membrane potential of a neuron?

Accepted Answer

It actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell, using ATP.

Question 2

A red blood cell is placed in a hypotonic solution. What is the most likely outcome, and why?

Accepted Answer

The cell will swell and may lyse because water will move into the cell.

Question 3

Which equation is used to calculate the equilibrium potential for a single ion, and what does a negative value indicate?

Accepted Answer

$$E_x = 61 \log \frac{[ion]_o}{[ion]_i}$$; a negative value means the inside of the cell is negative.

Question 4

Which of the following is a property of the plasma membrane described by the fluid mosaic model?

Accepted Answer

The membrane is dynamic, with proteins and lipids moving laterally within the bilayer.

Question 5

A patient has a genetic defect that prevents the formation of aquaporins in their cell membranes. Which process would be most directly affected?

Accepted Answer

Osmosis of water

Question 6

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

Accepted Answer

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

Question 7

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

Accepted Answer

Storing genetic information

Question 8

A cell is placed in a solution and begins to crenate (shrink). What can you infer about the tonicity of the solution relative to the cell cytosol?

Accepted Answer

The solution is hypertonic to the cytosol.

Question 9

Which of the following transport processes requires energy directly from ATP hydrolysis?

Accepted Answer

Primary active transport

Question 10

A cell uses a symporter to move glucose into the cell against its concentration gradient, using the energy from sodium ions moving down their gradient. This is an example of:

Accepted Answer

Secondary active transport

Question 11

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

Accepted Answer

It stabilizes the membrane structure during temperature changes.

Question 12

Given the following ion concentrations: $$[K^+]_{out} = 5 mM$$, $$[K^+]_{in} = 150 mM$$, calculate the equilibrium potential for potassium ($$E_{K^+}) $$using the Nernst equation: $$E_{K^+} = 61 \log \frac{[K^+]_{out}}{[K^+]_{in}}.$$

Accepted Answer

$$-90 mV$$

Question 13

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

It is a type of pinocytosis that concentrates specific molecules using receptors.

Question 14

If the 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

Net force is $$-130 mV$$; sodium will move into the cell.

Question 15

Which of the following is a real-life example of phagocytosis?

Accepted Answer

A white blood cell engulfing a bacterium

Question 16

Which of the following statements about the cytoskeleton is TRUE?

Accepted Answer

It provides structural support and helps transport substances within the cell.

Question 17

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

Accepted Answer

They are too large and hydrophilic to pass through the hydrophobic core of the phospholipid bilayer.

Question 18

Which of the following is a function of glycolipids and glycoproteins in the plasma membrane?

Accepted Answer

Facilitating cell recognition

Question 19

A cell is exposed to a toxin that inhibits all carrier proteins. Which of the following processes would be most directly affected?

Accepted Answer

Facilitated diffusion of glucose

Question 20

Which of the following best describes the difference between primary and secondary active transport?

Accepted Answer

Primary active transport uses ATP directly, while secondary active transport uses the energy stored in an ion gradient.

The Cell: Structure, Membrane Transport, and Membrane Potential

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