Question 1

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

Accepted Answer

It separates intracellular materials from extracellular fluids and regulates the movement of substances in and out of the cell.

Question 2

A red blood cell (RBC) has a diameter of approximately 7.5 micrometers. What is this value in millimeters? Use the conversion $1 	ext{ mm} = 1000 	ext{ \mu m}$.

Accepted Answer

$0.0075 	ext{ mm}$

Question 3

Which of the following statements about the fluid mosaic model of the plasma membrane is correct?

Accepted Answer

Proteins and carbohydrates are embedded in a double layer of lipids, allowing for flexibility and selective permeability.

Question 4

Which type of membrane protein is primarily responsible for the movement of sodium ($\mathrm{Na^+}$) and potassium ($\mathrm{K^+}$) ions across the cell membrane?

Accepted Answer

Integral proteins

Question 5

A scientist observes that two adjacent cells in cardiac muscle are connected by channels that allow ions to pass directly from one cell to another. Which type of cell junction is being observed?

Accepted Answer

Gap junction

Question 6

Which of the following best explains why steroid hormones (such as estrogen) can pass through the plasma membrane more easily than amino acid-based hormones?

Accepted Answer

Steroid hormones are lipid-soluble and can diffuse through the hydrophobic core of the lipid bilayer.

Question 7

Which organelle is responsible for packaging and delivering proteins within the cell, and consists of sacs called cisternae?

Accepted Answer

Golgi apparatus

Question 8

If a mutation caused all receptor proteins in a cell membrane to become nonfunctional, which process would be most directly affected?

Accepted Answer

Signal transduction

Question 9

Which of the following is NOT a function of the endoplasmic reticulum (ER)?

Accepted Answer

Packaging proteins for secretion (Golgi apparatus)

Question 10

A cell is observed to have a large number of ribosomes attached to its endoplasmic reticulum. What is the most likely function of this cell?

Accepted Answer

Active secretion of proteins

Question 11

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

Accepted Answer

It increases membrane rigidity and helps maintain cell shape.

Question 12

Which of the following statements about cell marker proteins is correct?

Accepted Answer

They are involved in cell identification and can act as antigens.

Question 13

A researcher is studying a tissue where the cells are tightly fused together to prevent leakage of extracellular fluid. Which type of intercellular junction is most likely present?

Accepted Answer

Tight junction

Question 14

Which of the following best explains why the plasma membrane is described as 'selectively permeable'?

Accepted Answer

It allows some substances to pass while restricting others based on size, charge, or solubility.

Question 15

Which of the following correctly matches the organelle with its function?

Accepted Answer

Golgi apparatus – protein packaging and delivery

Question 16

A cell is found to have defective integral proteins in its plasma membrane. Which of the following processes would be most directly impaired?

Accepted Answer

Transport of ions and molecules across the membrane

Question 17

Which of the following is a property of the hydrophobic tails of phospholipids in the plasma membrane?

Accepted Answer

They face the interior of the lipid bilayer, away from water.

Question 18

If a cell lacked functional desmosomes, which tissue property would be most affected?

Accepted Answer

Mechanical strength and resistance to stretching

Question 19

Which of the following best describes the difference between rough and smooth endoplasmic reticulum?

Accepted Answer

Rough ER has ribosomes attached and is involved in protein synthesis, while smooth ER lacks ribosomes and is involved in lipid synthesis.

Question 20

A mutation causes the hydrophilic heads of phospholipids in the plasma membrane to become hydrophobic. What is the most likely consequence for the cell?

Accepted Answer

The membrane would lose its bilayer structure, compromising cell integrity.

Cells: The Living Units – Structure and Function

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