Question 1

Which of the following best describes the effect of cholesterol on the fluidity of animal cell membranes at different temperatures?

Accepted Answer

Cholesterol stabilizes membrane fluidity by preventing excessive fluidity at high temperatures and excessive rigidity at low temperatures.

Question 2

A red blood cell is placed in a solution with a lower solute concentration than the cytoplasm. Which process will primarily occur, and what will be the result?

Accepted Answer

Osmosis; water will move into the cell, causing it to swell.

Question 3

Which of the following statements correctly distinguishes between channel proteins and carrier proteins in the plasma membrane?

Accepted Answer

Channel proteins form hydrophilic tunnels for specific molecules or ions, while carrier proteins bind to molecules and change shape to shuttle them across the membrane.

Question 4

Which of the following molecules is least likely to diffuse directly through the phospholipid bilayer of a cell membrane without the help of a transport protein?

Accepted Answer

Glucose

Question 5

A cell is placed in a solution and water moves out of the cell. Which of the following best describes the solution relative to the cell cytoplasm?

Accepted Answer

The solution is hypertonic to the cell.

Question 6

Which of the following best explains why facilitated diffusion does not require energy input from the cell?

Accepted Answer

Molecules move down their concentration gradient with the help of transport proteins.

Question 7

Which of the following scenarios best illustrates active transport?

Accepted Answer

A sodium ion ($$\mathrm{Na^+}) is $$pumped from an area of low concentration to an area of high concentration using ATP.

Question 8

Which of the following changes would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids.

Question 9

A patient is given an intravenous (IV) solution that is hypertonic relative to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

The red blood cells will shrink as water leaves the cells.

Question 10

Which of the following best describes the movement of water across a selectively permeable membrane?

Accepted Answer

Water moves from an area of low solute concentration to an area of high solute concentration by osmosis.

Question 11

A cell uses a transport protein to move glucose into the cell against its concentration gradient. Which process is being used?

Accepted Answer

Active transport

Question 12

Which of the following is a key difference between simple diffusion and facilitated diffusion?

Accepted Answer

Facilitated diffusion requires transport proteins, while simple diffusion does not.

Question 13

A plant cell is placed in a hypotonic solution. What will happen to the cell, and why?

Accepted Answer

The cell will swell but not burst due to the presence of the cell wall.

Question 14

Which of the following best explains why ions such as $$\mathrm{Na^+}$$ and $$\mathrm{K^+}$$ require transport proteins to cross the plasma membrane?

Accepted Answer

Ions are charged and cannot pass through the hydrophobic core of the membrane.

Question 15

Which of the following is an example of facilitated diffusion in human physiology?

Accepted Answer

Glucose entering a muscle cell via a GLUT transporter.

Question 16

A scientist observes that a certain molecule can cross the cell membrane only when a specific protein is present, and the process does not require ATP. Which type of transport is most likely occurring?

Accepted Answer

Facilitated diffusion

Question 17

Which of the following best describes the effect of increasing temperature on membrane fluidity?

Accepted Answer

Membrane fluidity increases as temperature increases.

Question 18

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the passive movement of water across a selectively permeable membrane from low to high solute concentration.

Question 19

A cell is placed in an isotonic solution. What will happen to the cell's volume over time?

Accepted Answer

The cell's volume will remain constant as there is no net movement of water.

Question 20

Which of the following best explains why a cell membrane is described as a 'fluid mosaic'?

Accepted Answer

The membrane is a dynamic structure with proteins and lipids that can move laterally within the layer.

Membrane Structure and Transport Mechanisms

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