Question 1

Which type of molecule is most likely to freely diffuse across a biological membrane without the aid of a transport protein?

Accepted Answer

Small, uncharged, nonpolar molecules

Question 2

A student is studying the movement of oxygen and glucose across the cell membrane. Which statement best explains why oxygen diffuses freely while glucose does not?

Accepted Answer

Oxygen is small and nonpolar, while glucose is large and polar.

Question 3

Which of the following molecules would require a transport protein to cross the plasma membrane?

Accepted Answer

Sodium ion (Na+)

Question 4

Which property prevents glucose from freely diffusing across the lipid bilayer?

Accepted Answer

It is large and polar.

Question 5

A researcher adds a solution of potassium ions (K+) to one side of a membrane. What is the most likely outcome?

Accepted Answer

Potassium ions will require a channel or transporter to cross the membrane.

Question 6

Which of the following best describes the permeability of the plasma membrane to small, uncharged, nonpolar molecules?

Accepted Answer

Highly permeable; they can freely diffuse.

Question 7

Why do ions such as Cl- and Na+ not freely diffuse across the cell membrane?

Accepted Answer

They are charged and hydrophilic.

Question 8

Which of the following statements is TRUE regarding the diffusion of water across the cell membrane?

Accepted Answer

Water is small and polar, so it can diffuse slowly or via aquaporins.

Question 9

A cell is placed in a solution containing urea, a small polar molecule. What is the most likely mechanism for urea to enter the cell?

Accepted Answer

Requires a specific transporter or channel.

Question 10

Which of the following molecules is LEAST likely to cross the plasma membrane by simple diffusion?

Accepted Answer

Glucose

Question 11

Which characteristic would most likely allow a molecule to pass through the cell membrane without assistance?

Accepted Answer

Small, uncharged, and nonpolar

Question 12

A patient is given a drug that is small and nonpolar. How will this drug most likely enter the cells?

Accepted Answer

By simple diffusion across the lipid bilayer

Question 13

Which of the following best explains why steroid hormones can easily cross the plasma membrane?

Accepted Answer

They are nonpolar and hydrophobic.

Question 14

Which of the following molecules would be most likely to require a membrane protein for transport into the cell?

Accepted Answer

Glucose

Question 15

A scientist observes that a certain molecule cannot cross the cell membrane unless a protein is present. Which property does this molecule most likely possess?

Accepted Answer

Large and polar

Question 16

Which of the following is a common misconception about the diffusion of molecules across the cell membrane?

Accepted Answer

All small molecules can freely diffuse regardless of polarity.

Question 17

Which of the following best describes the movement of ions across the cell membrane?

Accepted Answer

Ions require specific channels or transporters.

Question 18

A cell is exposed to a molecule that is large, uncharged, and hydrophilic. What is the most likely outcome?

Accepted Answer

The molecule will require a transporter to enter the cell.

Question 19

Which of the following molecules is most likely to diffuse rapidly across the cell membrane?

Accepted Answer

Oxygen (O2)

Question 20

Which property of the cell membrane allows nonpolar molecules to diffuse freely?

Accepted Answer

The hydrophobic core of the lipid bilayer

Membrane Permeability: Diffusion of Molecules Across the Cell Membrane

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