Question 1

Which of the following best describes a concentration gradient?

Accepted Answer

A difference in the concentration of a substance between two areas.

Question 2

In the context of diffusion, which direction do molecules naturally move?

Accepted Answer

From an area of high concentration to an area of low concentration.

Question 3

Which process requires energy input from the cell?

Accepted Answer

Movement of molecules against their concentration gradient.

Question 4

A cell is placed in a solution with a higher concentration of solute than inside the cell. What will most likely happen to water movement?

Accepted Answer

Water will move out of the cell toward the higher solute concentration.

Question 5

Which equation best represents the rate of diffusion ($R$) across a membrane, given concentration difference ($\Delta C$) and membrane permeability ($P$)?

Accepted Answer

$R = P 	imes \Delta C$

Question 6

Which of the following statements about equilibrium in diffusion is correct?

Accepted Answer

At equilibrium, there is no net movement of molecules across the membrane.

Question 7

A student adds a drop of dye to a beaker of water. After several minutes, the dye is evenly distributed. What process has occurred?

Accepted Answer

Diffusion

Question 8

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

Accepted Answer

Requires cellular energy (ATP)

Question 9

If a molecule moves 'against' its concentration gradient, what does this mean?

Accepted Answer

It moves from an area of low concentration to an area of high concentration.

Question 10

Which of the following best explains why energy is required for active transport?

Accepted Answer

Because molecules are moved against their concentration gradient.

Question 11

A cell membrane is described as 'semi-permeable.' What does this mean?

Accepted Answer

It allows some substances to pass through while blocking others.

Question 12

Which of the following scenarios best illustrates osmosis?

Accepted Answer

Water moves across a semi-permeable membrane from an area of low solute concentration to high solute concentration.

Question 13

If the concentration of a solute outside a cell is lower than inside, what will happen to the solute?

Accepted Answer

It will tend to move out of the cell by diffusion.

Question 14

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

Accepted Answer

Perfume molecules spreading throughout a room.

Question 15

A scientist measures the concentration of a dye in two regions of a beaker over time. She notices the concentrations become equal. What term best describes this final state?

Accepted Answer

Equilibrium

Question 16

Which of the following would increase the rate of diffusion across a membrane?

Accepted Answer

Increasing the concentration difference across the membrane.

Question 17

Which formula correctly expresses Fick's Law for diffusion rate ($J$) given area ($A$), concentration difference ($\Delta C$), and distance ($d$)?

Accepted Answer

$J = D 	imes \frac{A 	imes \Delta C}{d}$

Question 18

Which of the following statements about the energy required for diffusion is correct?

Accepted Answer

Diffusion does not require cellular energy because it is driven by kinetic energy of molecules.

Question 19

A patient receives an intravenous solution that is hypotonic compared to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

Water will enter the cells, causing them to swell.

Question 20

Which of the following is true about the movement of molecules at equilibrium?

Accepted Answer

Molecules continue to move randomly, but there is no net movement across the membrane.

Concentration Gradients and Diffusion in Anatomy & Physiology

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