$$\text{Water moves from}~[\text{low solute}]~\text{to}~[\text{high solute}]$$

Question 1

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

Accepted Answer

A flexible bilayer of phospholipids with proteins embedded and often grouped for common functions.

Question 2

What is the primary function of cholesterol in animal cell membranes?

Accepted Answer

It stabilizes membrane fluidity by reducing phospholipid movement at moderate temperatures and preventing solidification at low temperatures.

Question 3

A freshwater fish lives in cold environments. Which membrane adaptation would you expect in its cells?

Accepted Answer

A high proportion of unsaturated hydrocarbon tails in membrane phospholipids.

Question 4

Which of the following molecules can most easily cross the plasma membrane without the aid of a transport protein?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 5

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

Accepted Answer

It will lose water and shrivel.

Question 6

Which equation best represents the movement of water during osmosis across a selectively permeable membrane?

Accepted Answer

$$	ext{Water moves from}~[	ext{low solute}]~	ext{to}~[	ext{high solute}]$$

Question 7

Which type of membrane protein is most likely to be involved in signal transduction?

Accepted Answer

Integral protein

Question 8

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

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

Question 9

Which of the following is an example of active transport?

Accepted Answer

Sodium-potassium pump moving $$\mathrm{Na^+}$$ out and $$\mathrm{K^+}$$ into the cell using ATP.

Question 10

A plant cell is placed in a hypotonic solution. What is the expected outcome?

Accepted Answer

The cell will gain water and become turgid.

Question 11

Which process is responsible for the secretion of insulin from pancreatic cells?

Accepted Answer

Exocytosis

Question 12

Which of the following best explains why individuals lacking the CCR5 co-receptor are immune to HIV infection?

Accepted Answer

HIV cannot bind and enter immune cells without the CCR5 co-receptor.

Question 13

Which of the following is a function of membrane carbohydrates?

Accepted Answer

Acting as markers for cell identification and recognition.

Question 14

Which of the following statements about channel proteins is correct?

Accepted Answer

They provide a hydrophilic tunnel for specific molecules or ions to pass through the membrane.

Question 15

Which equation represents the energy input required for active transport by the sodium-potassium pump?

Accepted Answer

$$\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i}$$

Question 16

Which scenario best illustrates coupled transport (co-transport) in plant cells?

Accepted Answer

A proton pump creates an $$\mathrm{H^+}$$ gradient, which is used to actively transport sucrose into the cell.

Question 17

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

Accepted Answer

Synthesis of phospholipids

Question 18

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

Accepted Answer

It will remain stable.

Question 19

Which of the following best describes the movement of molecules during diffusion?

Accepted Answer

Molecules move down their concentration gradient until dynamic equilibrium is reached.

Question 20

Which of the following statements about facilitated diffusion is true?

Accepted Answer

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

Structure and Function of the Plasma Membrane

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