$$ATP \rightarrow ADP + P_i + \text{energy}$$

Question 1

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

Accepted Answer

A double layer of phospholipids with proteins and carbohydrates embedded and able to move laterally.

Question 2

Which component of the plasma membrane is primarily responsible for selective permeability?

Accepted Answer

Phospholipid bilayer

Question 3

A cell is placed in a solution with a higher concentration of solutes than inside the cell. Which process will most likely occur?

Accepted Answer

Water will leave the cell by osmosis, causing it to shrink.

Question 4

Which of the following molecules can most easily cross the plasma membrane by simple diffusion?

Accepted Answer

Oxygen ($$O_2)$$

Question 5

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

It requires transport proteins to move polar molecules across the membrane.

Question 6

Which equation best represents the movement of molecules during diffusion?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Question 7

Active transport is necessary for cells to:

Accepted Answer

Maintain internal concentrations of ions that differ from the extracellular environment.

Question 8

The sodium-potassium pump is an example of:

Accepted Answer

Electrogenic pump

Question 9

Which process involves the cell taking in macromolecules by forming vesicles from the plasma membrane?

Accepted Answer

Endocytosis

Question 10

A white blood cell engulfing a bacterium is an example of:

Accepted Answer

Phagocytosis

Question 11

Which of the following best explains why glucose requires a transport protein to cross the plasma membrane?

Accepted Answer

Glucose is a large, polar molecule and cannot pass through the hydrophobic core.

Question 12

Which type of membrane protein is most likely to be involved in cell-cell recognition?

Accepted Answer

Glycoprotein

Question 13

During receptor-mediated endocytosis, what is the role of the receptor?

Accepted Answer

To bind specific molecules and trigger vesicle formation for their uptake.

Question 14

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

Accepted Answer

Energy storage

Question 15

A cell uses ATP to move $$Na^+$$ ions out and $$K^+$$ ions in, maintaining a voltage across its membrane. This is an example of:

Accepted Answer

Active transport

Question 16

Which of the following statements about membrane carbohydrates is correct?

Accepted Answer

They are involved in cell-cell recognition and vary among species.

Question 17

Which process is used by cells to secrete hormones into the bloodstream?

Accepted Answer

Exocytosis

Question 18

Which of the following best describes cotransport?

Accepted Answer

Use of energy from one molecule moving down its gradient to transport another molecule against its gradient.

Question 19

A mutation causes a cell to lack functional channel proteins. Which process would be most directly affected?

Accepted Answer

Facilitated diffusion of ions

Question 20

Which of the following equations represents the energy provided by ATP hydrolysis for active transport?

Accepted Answer

$$ATP ightarrow ADP + P_i + 	ext{energy}$$

Membrane Transport and Cell Signaling: Structure and Function of the Plasma Membrane

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