Question 1

Which statement best describes the fluid-mosaic model of biological membranes?

Accepted Answer

Membranes are dynamic structures with proteins embedded in a fluid phospholipid bilayer, allowing lateral movement of components.

Question 2

A red blood cell is placed in a solution with a higher solute concentration than its cytoplasm. What will happen to the cell, and which term describes the solution?

Accepted Answer

The cell will shrink; the solution is hypertonic.

Question 3

Which of the following molecules can most easily cross the plasma membrane by simple diffusion?

Accepted Answer

Oxygen ($\mathrm{O_2}$)

Question 4

What is the primary function of the sodium-potassium pump in animal cells?

Accepted Answer

To actively transport $3\ \mathrm{Na^+}$ out of the cell and $2\ \mathrm{K^+}$ into the cell, maintaining electrochemical gradients.

Question 5

Which process describes the movement of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration?

Accepted Answer

Osmosis

Question 6

A plant cell is placed in pure water. What will happen to the cell, and why?

Accepted Answer

It will become turgid because water enters the cell due to the hypotonic environment.

Question 7

Which of the following best explains why cholesterol is important for membrane fluidity in animal cells?

Accepted Answer

Cholesterol maintains membrane fluidity by restricting phospholipid movement at high temperatures and preventing tight packing at low temperatures.

Question 8

Which type of membrane transport requires energy input from the cell and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 9

A patient is given a medication that inhibits proton pumps in the stomach lining. What effect will this likely have?

Accepted Answer

Decrease stomach acidity by reducing $\mathrm{H^+}$ secretion.

Question 10

Which of the following is NOT a component of the endomembrane system?

Accepted Answer

Mitochondrion

Question 11

Which statement correctly describes facilitated diffusion?

Accepted Answer

It uses transport proteins to move molecules down their concentration gradient.

Question 12

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

It will remain the same size because there is no net movement of water.

Question 13

Which of the following best describes the role of aquaporins in the cell membrane?

Accepted Answer

They facilitate the rapid movement of water across the membrane via facilitated diffusion.

Question 14

Which of the following is a real-life example of bulk transport in cells?

Accepted Answer

Engulfing bacteria by phagocytosis in white blood cells.

Question 15

Which equation best represents the osmotic pressure ($\Pi$) of a solution, where $C$ is the molar concentration, $R$ is the gas constant, and $T$ is the temperature in Kelvin?

Accepted Answer

$\Pi = CRT$

Question 16

Which of the following best explains why plant cells do not burst when placed in hypotonic solutions?

Accepted Answer

Plant cells have a rigid cell wall that provides structural support and limits expansion.

Question 17

Which of the following statements about the electrochemical gradient is correct?

Accepted Answer

It is the combined effect of the ion concentration gradient and the membrane potential.

Question 18

A cell uses a proton pump to create a gradient of $\mathrm{H^+}$ ions. How can this gradient be used to drive the uptake of another molecule, such as sucrose?

Accepted Answer

By coupling the movement of $\mathrm{H^+}$ ions down their gradient with the co-transport of sucrose into the cell.

Question 19

Which of the following is a function of the Golgi apparatus in eukaryotic cells?

Accepted Answer

Packaging and modifying proteins for secretion or delivery to other organelles.

Membrane Structure and Transport in Cells

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