Question 1

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

Accepted Answer

It acts as a selectively permeable barrier, controlling the movement of substances into and out of the cell.

Question 2

A scientist injects a dye that cannot cross the plasma membrane into the extracellular fluid surrounding a cell. After several hours, the dye is only found outside the cell. Which property of the plasma membrane does this experiment demonstrate?

Accepted Answer

Selective permeability

Question 3

Which of the following molecules is most responsible for the fluidity of the plasma membrane at normal body temperature?

Accepted Answer

Cholesterol

Question 4

The plasma membrane is described by the fluid mosaic model. Which statement best explains this model?

Accepted Answer

The membrane consists of a dynamic arrangement of lipids and proteins that can move laterally within the bilayer.

Question 5

Which of the following is a function of membrane proteins that is directly involved in cell recognition, such as in blood transfusions?

Accepted Answer

Cell-identity marker

Question 6

A patient receives a blood transfusion with mismatched blood type. Which plasma membrane component is most likely responsible for the immune reaction?

Accepted Answer

Glycoproteins acting as cell-identity markers

Question 7

Which equation best represents the permeability coefficient ($P$) of a membrane, given the membrane thickness ($d$) and the rate of diffusion ($D$)?

Accepted Answer

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

Question 8

Integral membrane proteins can function as channels. Which of the following ions is most likely to pass through a channel protein in the plasma membrane?

Accepted Answer

Potassium ($K^+$)

Question 9

The glycocalyx is a carbohydrate-rich region on the cell surface. Which of the following is NOT a function of the glycocalyx?

Accepted Answer

Acts as a rigid structural barrier

Question 10

Which of the following best explains why phospholipids form a bilayer in aqueous environments?

Accepted Answer

Phospholipids have both hydrophilic heads and hydrophobic tails, causing them to arrange with heads facing water and tails facing each other.

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

Active transport of glucose

Question 12

Which of the following best describes the role of cholesterol in the plasma membrane at low temperatures?

Accepted Answer

It increases membrane fluidity by preventing fatty acid tails from packing tightly.

Question 13

Which of the following is a correct sequence of the three main parts of a cell?

Accepted Answer

Plasma membrane, cytoplasm, nucleus

Question 14

A cell is placed in a solution containing a high concentration of nonpolar molecules. Which region of the plasma membrane will these molecules most likely accumulate in?

Accepted Answer

Hydrophobic interior

Question 15

Which of the following membrane proteins is most likely to be involved in the initial binding of the hormone insulin to a cell?

Accepted Answer

Receptor protein

Question 16

If a cell's plasma membrane loses its asymmetry, which of the following is most likely to occur?

Accepted Answer

The cell will lose its ability to maintain selective permeability.

Question 17

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

Accepted Answer

Proteins are either integral or peripheral, with integral proteins spanning the bilayer and peripheral proteins attached to the surface.

Question 18

Which of the following is a direct consequence of the lipid bilayer's amphipathic nature?

Accepted Answer

The membrane forms a stable barrier with hydrophilic heads facing water and hydrophobic tails facing inward.

Question 19

A cell exposed to a toxin that disrupts the hydrogen bonding between neighboring phospholipid heads will most likely experience which effect?

Accepted Answer

Increased membrane fluidity

Cell Structure and the Plasma Membrane: Foundations of Anatomy & Physiology

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