Question 1

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

Accepted Answer

A flexible bilayer of phospholipids with proteins and carbohydrates embedded and moving within it.

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which type of solution was the cell placed in, and what process caused this outcome?

Accepted Answer

Hypotonic solution; water moved into the cell by osmosis.

Question 3

Which of the following substances can most easily diffuse directly through the phospholipid bilayer of the cell membrane?

Accepted Answer

Small nonpolar molecules such as $$\mathrm{O_2$}$$ and $$\mathrm{CO_2$}$$

Question 4

Which of the following best explains why ions such as $$\mathrm{Na^+}$$ cannot freely cross the cell membrane?

Accepted Answer

They are repelled by the hydrophobic core of the membrane.

Question 5

Which of the following is an example of active transport?

Accepted Answer

Pumping $$\mathrm{Na^+}$$ out of a neuron using the sodium-potassium pump

Question 6

A cell is placed in a hypertonic solution. Predict what will happen to the cell and explain why.

Accepted Answer

The cell will shrink as water leaves by osmosis.

Question 7

Which statement correctly distinguishes between passive and active transport?

Accepted Answer

Passive transport moves substances down their concentration gradient without energy input, while active transport moves substances against their gradient using energy.

Question 8

Which of the following best describes the function of transmembrane transport proteins?

Accepted Answer

They provide channels or carriers for specific molecules to cross the membrane.

Question 9

A cell needs to import a large quantity of glucose, which is present at a higher concentration outside the cell than inside. Which transport mechanism is most likely used?

Accepted Answer

Facilitated diffusion via a glucose transporter protein

Question 10

Which equation correctly represents the calculation of concentration ($$C) in $$terms of moles of solute ($$n) $$and volume of solution ($$V$$)?

Accepted Answer

$$C = \frac{n}{V}$$

Question 11

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

Accepted Answer

Osmosis

Question 12

A white blood cell engulfs a bacterium by surrounding it with its plasma membrane and forming a vesicle. This process is best described as:

Accepted Answer

Endocytosis

Question 13

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 phospholipids

Question 14

Which of the following best describes the difference between diffusion and facilitated diffusion?

Accepted Answer

Facilitated diffusion requires a transport protein, while simple diffusion does not.

Question 15

A plant cell is placed in a solution and its central vacuole shrinks. What can you infer about the tonicity of the solution and the direction of water movement?

Accepted Answer

The solution is hypertonic; water moved out of the cell.

Question 16

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

Accepted Answer

Synthesizing proteins for export

Question 17

During exocytosis, which of the following occurs?

Accepted Answer

A vesicle fuses with the plasma membrane to release its contents outside the cell.

Question 18

Which of the following best explains how the endomembrane system contributes to protein secretion?

Accepted Answer

Proteins are synthesized in the rough ER, modified in the Golgi apparatus, and transported in vesicles to the plasma membrane for exocytosis.

Question 19

A mutation causes a cell's membrane to become less permeable to water. Which of the following is a likely consequence?

Accepted Answer

The cell will have difficulty maintaining osmotic balance.

Question 20

Which of the following scenarios best illustrates the concept of a concentration gradient?

Accepted Answer

A higher concentration of $$\mathrm{K^+}$$ ions inside the cell than outside

Cell Membranes: Structure, Function, and Transport Mechanisms

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