Question 1

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

Accepted Answer

A dynamic, flexible bilayer of phospholipids with proteins and carbohydrates that move laterally within the layer.

Question 2

Which component of the plasma membrane is primarily responsible for increasing membrane stability and fluidity?

Accepted Answer

Cholesterol

Question 3

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which of the following best describes the tonicity of the solution and the process occurring?

Accepted Answer

The solution is hypotonic; water is moving into the cell by osmosis.

Question 4

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 hydrophilic, so they cannot pass through the hydrophobic core of the bilayer.

Question 5

Which of the following equations correctly represents the calculation of osmolarity for a 1 mM NaCl solution?

Accepted Answer

$$1\ \mathrm{mM\ NaCl} = 2\ \mathrm{mOsm}$$

Question 6

A patient is given an intravenous solution of 0.9% NaCl. What effect will this have on their red blood cells, and why?

Accepted Answer

Cells will remain the same size because the solution is isotonic.

Question 7

Which of the following is a function of membrane glycoproteins in the plasma membrane?

Accepted Answer

They serve as identification tags for cell recognition.

Question 8

Which of the following best describes the process of secondary active transport?

Accepted Answer

It relies on the energy stored in ionic gradients created by primary active transport to move other substances.

Question 9

Which of the following scenarios best illustrates the principle of selective permeability of the plasma membrane?

Accepted Answer

Oxygen and carbon dioxide diffuse freely, but glucose requires a carrier protein to enter the cell.

Question 10

A cell is placed in a solution containing a high concentration of nonpenetrating solutes. What will happen to the cell, and what is the underlying mechanism?

Accepted Answer

The cell will shrink due to water moving out of the cell by osmosis.

Question 11

Which of the following best describes the role of the Na$$ ^+ /K$ ^+ $$ ATPase pump in maintaining membrane potential?

Accepted Answer

It pumps Na$$ ^+ $$ out of the cell and K$$ ^+ $$ into the cell against their concentration gradients using ATP.

Question 12

Which of the following is an example of carrier-mediated facilitated diffusion?

Accepted Answer

Transport of glucose into a muscle cell via a specific protein carrier.

Question 13

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the movement of water from an area of higher water concentration to an area of lower water concentration across a semipermeable membrane.

Question 14

Which of the following best explains why a solution of 1 mM CaCl$$_2$$ has a higher osmolarity than a solution of 1 mM glucose?

Accepted Answer

CaCl$$_2$$ dissociates into three ions, increasing the number of particles in solution.

Question 15

A cell is exposed to a toxin that inhibits all ATP production. Which of the following transport processes would be most directly affected?

Accepted Answer

Active transport of Na$$ ^+ $$ and K$$ ^+ $$ via Na$$ ^+ /K$ ^+ $$ ATPase

Question 16

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

A selective process where specific molecules bind to receptors and are internalized by the cell.

Question 17

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

Accepted Answer

Storing genetic information for the cell.

Question 18

A patient with severe edema is treated with a hypertonic saline solution. What is the physiological rationale for this treatment?

Accepted Answer

The hypertonic solution will draw water out of the tissues into the bloodstream, reducing swelling.

Question 19

Which of the following best describes the difference between primary and secondary active transport?

Accepted Answer

Primary active transport uses ATP directly, while secondary active transport uses the energy from ATP indirectly via ionic gradients.

Cellular Physiology: Plasma Membrane Structure and Transport Mechanisms

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