Question 1

Which of the following best describes the function of the plasma membrane in a typical human cell?

Accepted Answer

It is a selectively permeable barrier that regulates the movement of substances into and out of the cell.

Question 2

The lipid bilayer of the plasma membrane is primarily composed of which type of molecules?

Accepted Answer

Phospholipids

Question 3

A molecule with both hydrophilic and hydrophobic regions is described as:

Accepted Answer

Amphipathic

Question 4

Which of the following statements about membrane proteins is correct?

Accepted Answer

Peripheral proteins are attached to the membrane surface and do not span the bilayer.

Question 5

A patient receives a blood transfusion. Why is it important that the donor and recipient have compatible cell-identity markers?

Accepted Answer

To prevent the recipient's immune system from attacking the donor cells.

Question 6

Which equation best represents the permeability of the plasma membrane to a solute?

Accepted Answer

$$P = \frac{D \cdot K}{d}$$

Question 7

If a cell is placed in a solution with a lower concentration of solutes than its cytosol, what will happen?

Accepted Answer

Water will move into the cell, causing it to swell.

Question 8

Which of the following membrane proteins is most likely to function as a channel for potassium ions ($$K^+$$)?

Accepted Answer

Integral protein

Question 9

Cholesterol in the plasma membrane primarily serves to:

Accepted Answer

Increase membrane fluidity at low temperatures and decrease it at high temperatures.

Question 10

Which of the following best explains why water molecules can pass through the plasma membrane despite being polar?

Accepted Answer

Water molecules are small enough to pass through transient gaps in the lipid bilayer.

Question 11

A mutation causes a cell to produce defective carrier proteins in its plasma membrane. Which process would be most directly affected?

Accepted Answer

Transport of specific molecules such as glucose across the membrane.

Question 12

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

Accepted Answer

Cell recognition and signaling

Question 13

If the concentration of cholesterol in a cell membrane increases, what is the most likely effect on membrane permeability to small polar molecules?

Accepted Answer

Permeability will decrease.

Question 14

Which of the following best describes the arrangement of phospholipids in the plasma membrane?

Accepted Answer

Hydrophilic heads face outward toward the aqueous environment, and hydrophobic tails face inward.

Question 15

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

Accepted Answer

Synthesizing proteins for the cell

Question 16

A cell is exposed to a toxin that disrupts the lipid bilayer, causing increased permeability. Which of the following is a likely consequence?

Accepted Answer

Uncontrolled movement of ions and molecules into and out of the cell

Question 17

Which of the following best describes the role of integral proteins in the plasma membrane?

Accepted Answer

They span the membrane and can function as channels or carriers for specific molecules.

Question 18

Which of the following would most likely increase the fluidity of a cell membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids

Question 19

Which of the following is true regarding the permeability of the plasma membrane to oxygen ($$O_2) $$and carbon dioxide ($$CO_2$$)?

Accepted Answer

Both $$O_2$$ and $$CO_2$$ can easily diffuse through the lipid bilayer because they are nonpolar.

The Structure and Function of the Plasma Membrane

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