Question 1

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

Accepted Answer

It maintains the cell's integrity and controls the movement of substances between the cell and its environment.

Question 2

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

Accepted Answer

$0.0075\ mm$

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 bilayer of phospholipids, allowing for flexibility and selective permeability.

Question 4

A patient is diagnosed with a genetic disorder that affects the function of integral proteins responsible for sodium ($Na^+$) and potassium ($K^+$) transport. Which cellular process is most likely to be directly impaired?

Accepted Answer

Maintenance of membrane potential

Question 5

Which type of cell junction would you expect to find in the lining of the gastrointestinal (G.I.) tract to prevent leakage between cells?

Accepted Answer

Tight junction

Question 6

A scientist observes that certain cells in cardiac muscle are able to rapidly transmit electrical signals to adjacent cells. Which type of intercellular junction is primarily responsible for this function?

Accepted Answer

Gap junctions

Question 7

Which of the following best explains why steroid hormones (such as estrogen) can easily pass through the plasma membrane?

Accepted Answer

They are lipid-soluble and can diffuse through the lipid bilayer.

Question 8

Which organelle is primarily responsible for packaging and delivering proteins within the cell?

Accepted Answer

Golgi apparatus

Question 9

A mutation causes the loss of receptor proteins in the plasma membrane. Which of the following cellular processes would be most directly affected?

Accepted Answer

Signal transduction in response to external stimuli

Question 10

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

Accepted Answer

It provides rigidity and stability to the membrane structure.

Question 11

A researcher is studying a tissue sample and observes that the cells are connected by spot weld-like structures. Which type of junction is being observed?

Accepted Answer

Desmosome

Question 12

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

Accepted Answer

Packaging proteins for export (Golgi apparatus)

Question 13

If a cell's ribosomes were destroyed, which process would be most directly affected?

Accepted Answer

Protein synthesis

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

A cell is observed to have a large number of rough endoplasmic reticulum (RER). What is the most likely function of this cell?

Accepted Answer

Protein synthesis for export

Question 16

Which of the following is a correct sequence of structures that a newly synthesized protein would pass through before being secreted from the cell?

Accepted Answer

Ribosome → Rough ER → Golgi apparatus → Plasma membrane

Question 17

Which of the following best describes the function of cell marker proteins (cell antigens) in the plasma membrane?

Accepted Answer

They identify the cell to other cells and the immune system.

Question 18

A scientist is studying a cell that is highly flexible and can change shape easily. Which component of the plasma membrane is most responsible for this property?

Accepted Answer

Phospholipid bilayer

Question 19

Which of the following statements about the cytoplasm is correct?

Accepted Answer

It is the site of protein synthesis and contains the cell's organelles suspended in cytosol.

Question 20

A cell is observed to have abundant smooth endoplasmic reticulum (SER). Which function is this cell most likely specialized for?

Accepted Answer

Lipid synthesis and detoxification

Cells: The Living Units – Structure and Function

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