Question 1

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic bilayer of amphipathic phospholipids with proteins and other molecules embedded and moving laterally.

Question 2

How does cholesterol affect membrane fluidity at different temperatures in animal cells?

Accepted Answer

It reduces membrane fluidity at moderate temperatures but prevents solidification at low temperatures.

Question 3

A red blood cell is placed in a solution and swells until it bursts. Which of the following best describes the tonicity of the solution and the direction of water movement?

Accepted Answer

The solution is hypotonic; water moves into the cell.

Question 4

Which of the following molecules is most likely to diffuse directly through the lipid bilayer of a plasma membrane without the aid of a transport protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 5

What is the main function of glycoproteins and glycolipids in the plasma membrane?

Accepted Answer

Serving as markers for cell recognition and identification

Question 6

A plant cell is placed in a hypertonic solution. What will most likely happen to the cell?

Accepted Answer

It will undergo plasmolysis as the plasma membrane pulls away from the cell wall.

Question 7

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

Accepted Answer

It moves substances down their concentration gradient through transport proteins.

Question 8

The sodium-potassium pump is an example of which type of membrane transport, and what is its main function?

Accepted Answer

Active transport; it maintains high $$K^+$$ and low $$Na^+$$ concentrations inside animal cells using ATP.

Question 9

Which of the following best describes the process of receptor-mediated endocytosis?

Accepted Answer

The cell selectively takes in specific molecules that bind to receptors on the plasma membrane.

Question 10

Which of the following statements about membrane proteins is correct?

Accepted Answer

Transmembrane proteins are a type of integral protein that span the lipid bilayer.

Question 11

A cell is placed in an isotonic solution. What will happen to the movement of water across the plasma membrane?

Accepted Answer

Water will move in and out of the cell at equal rates.

Question 12

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

Accepted Answer

They are charged and cannot pass through the hydrophobic interior of the lipid bilayer.

Question 13

Which of the following is an example of cotransport in plant cells?

Accepted Answer

A proton pump creating an $$H^+$$ gradient that drives the active transport of sucrose into the cell.

Question 14

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

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the membrane.

Question 15

A patient with familial hypercholesterolemia has high blood cholesterol because:

Accepted Answer

Their cells have defective LDL receptor proteins and cannot take up cholesterol efficiently.

Question 16

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

Accepted Answer

They allow rapid passive movement of water molecules across the membrane.

Question 17

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesis of phospholipids

Question 18

If a cell is placed in a solution where the solute concentration is lower outside the cell than inside, what will happen?

Accepted Answer

Water will move into the cell, causing it to swell.

Question 19

Which of the following best explains why the plasma membrane is described as selectively permeable?

Accepted Answer

It allows some substances to cross more easily than others due to the lipid bilayer and specific transport proteins.

Question 20

Which of the following processes requires energy input from the cell?

Accepted Answer

Active transport of $$Na^+$$ and $$K^+$$ via the sodium-potassium pump

Membrane Structure and Function: Study Notes (Campbell Biology, Chapter 7)

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