Q: Which equation best represents Fick's Law of Diffusion, describing the rate of diffusion ($$J) $$across a membrane?

$$J = D \times (C_1$ - C_2$) / d$$

Question 1

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

Accepted Answer

It acts as a selective barrier, regulating the movement of substances into and out of the cell.

Question 2

Which type of membrane protein is most likely to function as a channel for ions to pass through the plasma membrane?

Accepted Answer

Integral protein

Question 3

A patient is experiencing swelling due to excess fluid accumulation in the extracellular space. Which extracellular material is most likely contributing to the adhesion of cells and retention of fluid?

Accepted Answer

Extracellular matrix

Question 4

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

Accepted Answer

Synthesis of DNA

Question 5

Which cell junction allows for the passage of ions and small molecules directly between adjacent cells, facilitating rapid communication?

Accepted Answer

Gap junction

Question 6

A researcher observes that a certain molecule can cross the plasma membrane without the aid of a protein and moves from an area of high concentration to low concentration. Which process is being described?

Accepted Answer

Simple diffusion

Question 7

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

Accepted Answer

Increasing the difference in concentration across the membrane

Question 8

Which equation best represents Fick's Law of Diffusion, describing the rate of diffusion ($$J) $$across a membrane?

Accepted Answer

$$J = D 	imes (C_1$ - C_2$) / d$$

Question 9

A mutation causes a cell to lack glycoproteins on its plasma membrane. Which function would be most directly affected?

Accepted Answer

Cell-cell recognition

Question 10

Which of the following statements about the lipid bilayer of the plasma membrane is correct?

Accepted Answer

Phospholipids have hydrophilic heads and hydrophobic tails.

Question 11

Which scenario best illustrates the concept of selective permeability of the plasma membrane?

Accepted Answer

Water and small nonpolar molecules can pass freely, but ions require specific channels.

Question 12

A cell is placed in a solution containing a high concentration of glucose. Glucose is too large to pass through the membrane by simple diffusion. Which process will most likely allow glucose to enter the cell?

Accepted Answer

Facilitated diffusion

Question 13

Which of the following is a real-world example of homeostatic imbalance related to the plasma membrane?

Accepted Answer

A patient with cystic fibrosis has defective chloride channels, leading to thick mucus production.

Question 14

Which of the following best describes the role of tight junctions in epithelial tissue?

Accepted Answer

They prevent leakage of extracellular fluid between cells.

Question 15

Which membrane protein function is most directly involved in the immune system's ability to distinguish self from non-self?

Accepted Answer

Cell-cell recognition

Question 16

A cell is observed to have a large number of desmosomes. Which tissue type is this cell most likely a part of?

Accepted Answer

Epithelial tissue subject to mechanical stress, such as skin

Question 17

Which of the following statements about passive membrane transport is correct?

Accepted Answer

It relies on the kinetic energy of molecules and moves substances down their concentration gradient.

Question 18

Which equation best describes the relationship between the rate of diffusion ($$R) $$and the surface area ($$A) of $$the membrane?

Accepted Answer

$$R \propto A$$

Question 19

A cell is exposed to a toxin that disrupts the attachment of membrane proteins to the cytoskeleton. Which cellular function would be most directly impaired?

Accepted Answer

Cell shape and stability

Question 20

Which of the following best explains why oxygen can diffuse rapidly across the plasma membrane?

Accepted Answer

Oxygen is a small nonpolar molecule.

Cells: The Living Units – Structure and Function of the Plasma Membrane

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