Question 1

Which of the following best describes the 'fluid mosaic model' of the plasma membrane? (Concept 7.1)

Accepted Answer

The membrane consists of a phospholipid bilayer with proteins and other molecules embedded and able to move laterally, creating a dynamic and flexible structure.

Question 2

Which of the following molecules would be least likely to diffuse passively across a plasma membrane without the help of a transport protein? (Concept 7.2)

Accepted Answer

Glucose

Question 3

A red blood cell is placed in a 0.2 M sucrose solution. The cell shrinks and becomes crenated. What is the best explanation for this observation? (Concept 7.3)

Accepted Answer

The sucrose solution is hypertonic to the cell, causing water to leave the cell by osmosis.

Question 4

Which of the following statements about facilitated diffusion is correct? (Concept 7.4)

Accepted Answer

Facilitated diffusion uses transport proteins to move solutes down their concentration gradient.

Question 5

Which of the following best describes the function of cholesterol in animal cell membranes? (Concept 7.1)

Accepted Answer

Cholesterol stabilizes membrane fluidity by preventing tight packing at low temperatures and restraining movement at high temperatures.

Question 6

A plant cell is placed in distilled water. What will happen to the cell? (Concept 7.3)

Accepted Answer

The cell will gain water, become turgid, and the cell wall will prevent bursting.

Question 7

Which of the following is NOT a function of membrane proteins? (Concept 7.1)

Accepted Answer

Energy storage

Question 8

A sodium-potassium pump moves sodium and potassium ions across the plasma membrane. Which of the following statements about this pump is correct? (Concept 7.4)

Accepted Answer

It requires ATP to move sodium out of the cell and potassium into the cell against their concentration gradients.

Question 9

Which of the following best describes the mechanism by which Ca$$^{2+}$$ enters the cell? (Concept 7.4)

Accepted Answer

Facilitated diffusion through a specific channel protein

Question 10

If a cell is placed in a solution with a higher concentration of solutes than inside the cell, what will happen to the cell? (Concept 7.3)

Accepted Answer

The cell will lose water and shrink.

Question 11

Which of the following statements about osmosis is correct? (Concept 7.3)

Accepted Answer

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

Question 12

Which of the following would increase the rate of diffusion of a substance across a biological membrane? (Concept 7.2)

Accepted Answer

Increasing the concentration gradient of the substance

Question 13

Which of the following statements about active transport is correct? (Concept 7.4)

Accepted Answer

Active transport requires energy, usually in the form of ATP.

Question 14

A cell is placed in a solution and water moves into the cell by osmosis. Which of the following best describes the solution? (Concept 7.3)

Accepted Answer

The solution is hypotonic to the cell.

Question 15

Which of the following statements about membrane carbohydrates is correct? (Concept 7.1)

Accepted Answer

Membrane carbohydrates are involved in cell-cell recognition.

Question 16

Which of the following best explains why ions such as Na$$^+$$ and K$$^+$$ cannot diffuse freely across the plasma membrane? (Concept 7.2)

Accepted Answer

They are charged and cannot pass through the hydrophobic core of the membrane without the help of transport proteins.

Question 17

Which of the following is a real-world example of active transport in human physiology? (Concept 7.4)

Accepted Answer

Glucose being absorbed from the gut into intestinal epithelial cells against its concentration gradient

Question 18

Which of the following statements about the sodium-potassium pump is correct? (Concept 7.4)

Accepted Answer

It moves three sodium ions out of the cell and two potassium ions into the cell, using ATP.

Question 19

Which of the following best describes the role of aquaporins in the plasma membrane? (Concept 7.2)

Accepted Answer

They facilitate the rapid diffusion of water across the membrane.

Plasma Membrane Structure and Transport Mechanisms in General Biology

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