Question 1

Which of the following best describes the main function of the plasma membrane in maintaining homeostasis?

Accepted Answer

It selectively controls which molecules enter and leave the cell, allowing exchange with the environment.

Question 2

A red blood cell is placed in a solution containing 2.0 Osm/L NaCl. The osmolarity of the cell is 0.3 Osm/L. What will happen to the cell, and why?

Accepted Answer

The cell will shrink because water will move out of the cell into the hypertonic solution.

Question 3

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

Accepted Answer

Small nonpolar molecules such as $ O_2 $ and $ CO_2 $

Question 4

A cell is placed in a 0.3 M solution of CaCl$_2$. What is the osmolarity of this solution?

Accepted Answer

$ 0.3 	imes 3 = 0.9 $ Osm/L

Question 5

Which of the following statements about facilitated diffusion is TRUE?

Accepted Answer

It uses membrane proteins to move hydrophilic molecules down their concentration gradient.

Question 6

What is the main difference between primary and secondary active transport?

Accepted Answer

Primary active transport uses ATP directly, while secondary active transport uses the energy stored in ion gradients.

Question 7

A cell is placed in a solution containing 1 M glucose. What is the osmolarity of this solution?

Accepted Answer

$ 1 	imes 1 = 1 $ Osm/L

Question 8

Which of the following best describes osmosis?

Accepted Answer

The movement of water molecules from an area of low solute concentration to high solute concentration across a selectively permeable membrane.

Question 9

Which of the following is an example of secondary active transport?

Accepted Answer

Glucose being transported into a cell using the energy from a sodium ion gradient.

Question 10

A cell is placed in a solution that is hypotonic relative to its cytoplasm. What will happen to the cell?

Accepted Answer

The cell will swell as water enters the cell.

Question 11

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It moves 3 sodium ions out of the cell and 2 potassium ions in, using ATP.

Question 12

Which of the following factors would increase the rate of diffusion across a cell membrane?

Accepted Answer

Increasing the concentration gradient.

Question 13

Which of the following best explains why ions such as Na+ cannot cross the plasma membrane by simple diffusion?

Accepted Answer

They are charged and require membrane proteins to cross the hydrophobic core.

Question 14

A cell is placed in a 0.3 M NaCl solution. What is the osmolarity of this solution, and how does it compare to a cell with 0.3 Osm/L cytoplasm?

Accepted Answer

$ 0.3 	imes 2 = 0.6 $ Osm/L; the solution is hypertonic to the cell.

Question 15

Which of the following transport mechanisms requires energy input from the cell?

Accepted Answer

Active transport

Question 16

Which of the following best describes the process of exocytosis?

Accepted Answer

The release of substances from the cell by fusion of vesicles with the plasma membrane.

Question 17

If a cell is placed in a solution containing 0.3 M glucose and 0.3 M NaCl, what is the total osmolarity of the solution?

Accepted Answer

$ 0.3 + (0.3 	imes 2) = 0.9 $ Osm/L

Question 18

Which of the following is NOT a characteristic of passive transport?

Accepted Answer

It requires membrane proteins for all substances.

Question 19

Which of the following scenarios best illustrates the concept of tonicity?

Accepted Answer

A cell placed in a hypertonic solution shrinks due to water loss.

Question 20

Which of the following statements about bulk transport is correct?

Accepted Answer

Endocytosis and exocytosis are forms of bulk transport that require energy.

Transport Across the Cell Membrane: Mechanisms and Principles

Study Guide - Practice Questions