Question 1

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

Accepted Answer

A double layer of phospholipids with scattered proteins that can move laterally within the layer.

Question 2

Why are phospholipids critical for the selective permeability of the cell membrane?

Accepted Answer

Their hydrophilic heads and hydrophobic tails form a bilayer that blocks most polar and charged molecules, allowing only small, nonpolar molecules to pass.

Question 3

Which of the following molecules can pass directly through the phospholipid bilayer without the help of a membrane protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

A patient has a genetic defect that prevents the formation of tight junctions in their intestinal cells. Which of the following is a likely consequence?

Accepted Answer

Water and water-soluble chemicals can leak between cells, compromising the intestinal barrier.

Question 5

Which type of cell junction is most abundant in tissues subjected to mechanical stress, such as the skin and heart muscle?

Accepted Answer

Desmosomes

Question 6

Gap junctions are essential for which of the following physiological processes?

Accepted Answer

Allowing synchronized electrical activity in cardiac muscle

Question 7

Which of the following best describes the function of integral membrane proteins?

Accepted Answer

They are firmly embedded in the membrane and can function as channels, receptors, or enzymes.

Question 8

A scientist is studying a membrane protein that catalyzes the hydrolysis of a peptide bond. What type of protein is this and what is its function?

Accepted Answer

Integral protein; enzymatic activity

Question 9

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

Accepted Answer

Storing genetic information

Question 10

A mutation causes a cell to lack cholesterol in its plasma membrane. Which of the following is the most likely effect?

Accepted Answer

The membrane will become too fluid and less structurally stable.

Question 11

Which of the following best explains why large, polar molecules cannot pass directly through the phospholipid bilayer?

Accepted Answer

The hydrophobic core of the bilayer repels polar and charged molecules.

Question 12

Which of the following is a real-life example of the importance of tight junctions?

Accepted Answer

They prevent the leakage of digestive enzymes between cells in the intestines.

Question 13

Which of the following best describes the role of desmosomes in tissue integrity?

Accepted Answer

They anchor adjacent cells together, providing mechanical strength.

Question 14

A researcher observes that certain cells can rapidly exchange ions and small molecules. Which type of cell junction is most likely responsible for this observation?

Accepted Answer

Gap junctions

Question 15

Which of the following is a correct sequence in the levels of biological organization from smallest to largest?

Accepted Answer

Atom → Macromolecule → Cell → Tissue → Organ → Organ System → Organism

Question 16

Which of the following best explains why enzymes are considered biological catalysts?

Accepted Answer

They increase the rate of chemical reactions without being consumed in the process.

Question 17

A drug is designed to block the function of gap junctions in cardiac muscle. What is the most likely effect on heart function?

Accepted Answer

The heart will lose its ability to contract in a coordinated manner.

Question 18

Which of the following statements about peripheral membrane proteins is correct?

Accepted Answer

They are loosely associated with the membrane and often function as enzymes or in cell signaling.

Question 19

Which of the following best describes the function of the plasma membrane in displaying and secreting biological markers?

Accepted Answer

It allows the cell to be recognized by other cells and the immune system.

Cell Membrane Structure, Function, and Cellular Junctions

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