Q: Which of the following equations correctly represents the rate of simple diffusion across a membrane?

$\text{Rate of diffusion} = \text{surface area} \times \text{concentration gradient} \times \text{membrane permeability}$

Q: Which of the following is an example of primary active transport?

Na\textsuperscript{+}/K\textsuperscript{+} ATPase pumping Na\textsuperscript{+} out and K\textsuperscript{+} in using ATP

Q: A cell uses the Na\textsuperscript{+}/glucose symporter to bring glucose into the cell against its concentration gradient. Which type of transport is this, and what is the energy source?

Secondary active transport; energy from Na\textsuperscript{+} gradient

Q: A cell is exposed to a toxin that blocks all ATP production. Which of the following transport processes will be most directly affected?

Na\textsuperscript{+}/K\textsuperscript{+} ATPase activity

Question 1

Which of the following best describes the difference between osmolarity and tonicity?

Accepted Answer

Osmolarity is the total solute particle concentration (penetrating and non-penetrating), while tonicity describes the effect of a solution on cell volume and depends only on non-penetrating solutes.

Question 2

A red blood cell is placed in a solution containing 300 mOsm/L of urea (a penetrating solute) and 150 mOsm/L of NaCl (a non-penetrating solute). What will happen to the cell?

Accepted Answer

The cell will swell because the solution is hypotonic.

Question 3

Which of the following equations correctly represents the rate of simple diffusion across a membrane?

Accepted Answer

$	ext{Rate of diffusion} = 	ext{surface area} 	imes 	ext{concentration gradient} 	imes 	ext{membrane permeability}$

Question 4

Which of the following substances is most likely to cross the cell membrane by simple diffusion?

Accepted Answer

O	extsubscript{2} (oxygen)

Question 5

A patient is given an intravenous solution that is isotonic in terms of osmolarity but contains only penetrating solutes. What is the likely effect on the patient's red blood cells?

Accepted Answer

Cells will swell and possibly lyse.

Question 6

Which of the following best describes the function of carrier proteins in the cell membrane?

Accepted Answer

They change conformation to move specific molecules across the membrane, often at a slower rate than channels.

Question 7

Which of the following is an example of primary active transport?

Accepted Answer

Na	extsuperscript{+}/K	extsuperscript{+} ATPase pumping Na	extsuperscript{+} out and K	extsuperscript{+} in using ATP

Question 8

A cell uses the Na	extsuperscript{+}/glucose symporter to bring glucose into the cell against its concentration gradient. Which type of transport is this, and what is the energy source?

Accepted Answer

Secondary active transport; energy from Na	extsuperscript{+} gradient

Question 9

Which of the following statements about channel proteins is TRUE?

Accepted Answer

Their selectivity is determined by the size of the pore and the charge of amino acids lining the pore.

Question 10

A cell is exposed to a toxin that blocks all ATP production. Which of the following transport processes will be most directly affected?

Accepted Answer

Na	extsuperscript{+}/K	extsuperscript{+} ATPase activity

Question 11

Which of the following best explains why facilitated diffusion exhibits saturation kinetics?

Accepted Answer

Because the rate of transport depends on the number of available carrier proteins, which can become fully occupied.

Question 12

Which of the following is a key difference between endocytosis and exocytosis?

Accepted Answer

Endocytosis involves vesicle formation from the plasma membrane to bring substances into the cell, while exocytosis releases substances from vesicles to the extracellular space.

Question 13

Which of the following scenarios best illustrates the concept of competition in carrier-mediated transport?

Accepted Answer

A carrier protein transports both glucose and galactose, but the presence of galactose reduces the rate of glucose transport.

Question 14

Which of the following is TRUE regarding vesicular transport?

Accepted Answer

It requires ATP and is used for transporting large molecules or particles.

Question 15

A cell is placed in a solution containing 200 mOsm/L of non-penetrating solutes and 100 mOsm/L of penetrating solutes. What is the tonicity of the solution relative to the cell?

Accepted Answer

Hypotonic

Question 16

Which of the following best describes the mechanism of the Na	extsuperscript{+}/Ca	extsuperscript{2+} exchanger (NCX) in cardiac muscle cells?

Accepted Answer

It is an antiporter that uses the Na	extsuperscript{+} gradient to move Ca	extsuperscript{2+} out of the cell against its gradient.

Question 17

Which of the following is NOT a property of diffusion?

Accepted Answer

It requires an input of energy from ATP.

Question 18

Which of the following best explains why non-penetrating solutes determine tonicity?

Accepted Answer

Because they cannot cross the membrane, they create an osmotic gradient that causes water to move.

Question 19

Which of the following is an example of facilitated diffusion?

Accepted Answer

Glucose transport into a muscle cell via GLUT transporter

Question 20

A cell is exposed to a solution with a high concentration of non-penetrating solutes. What is the most likely effect on the cell?

Accepted Answer

The cell will shrink due to water efflux.

Cell Membrane Transport: Mechanisms and Principles

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