Question 1

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic structure with proteins and cholesterol embedded in a fluid phospholipid bilayer.

Question 2

What is the primary function of glycoproteins in the plasma membrane?

Accepted Answer

To serve as identification tags recognized by other cells.

Question 3

Which of the following molecules can most easily diffuse directly through the phospholipid bilayer of a cell membrane?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

Cholesterol is found within animal cell membranes. What is its main role?

Accepted Answer

To stabilize membrane fluidity at different temperatures.

Question 5

A cell is placed in a solution containing 2% sucrose, while the cytoplasm contains 0.5% sucrose. The membrane is not permeable to sucrose. What will happen to the cell?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 6

Which of the following best explains why unsaturated fatty acids help maintain membrane fluidity at lower temperatures?

Accepted Answer

Their kinks prevent phospholipids from packing closely together.

Question 7

Which type of membrane protein is responsible for relaying signals from outside the cell to the inside?

Accepted Answer

Receptor proteins

Question 8

A dialysis bag containing 0.4 M sucrose is placed in a beaker of pure water. The bag is permeable to water but not to sucrose. What will happen to the mass of the bag?

Accepted Answer

The bag will gain mass as water enters.

Question 9

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It requires specific transport proteins but does not require energy.

Question 10

Which equation best represents the direction of net diffusion for a solute across a membrane?

Accepted Answer

$$J = -D \frac{dC}{dx}$$, where $$J is $$the flux, $$D is $$the diffusion coefficient, and $$\frac{dC}{dx} is $$the concentration gradient.

Question 11

Which of the following is an example of active transport?

Accepted Answer

Movement of $$Na^+$$ ions from low to high concentration using ATP

Question 12

What would happen to an animal cell placed in a hypotonic solution?

Accepted Answer

It would gain water and potentially burst (lyse).

Question 13

Which process is used by cells to export large molecules such as proteins?

Accepted Answer

Exocytosis

Question 14

A plant cell in a hypertonic environment will:

Accepted Answer

Lose water and undergo plasmolysis.

Question 15

Which of the following best describes osmoregulation?

Accepted Answer

The mechanism organisms use to maintain water balance within their cells.

Question 16

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

Accepted Answer

Forming rigid barriers to prevent all molecule movement.

Question 17

Which type of endocytosis involves the specific binding of molecules to membrane receptors before being engulfed?

Accepted Answer

Receptor-mediated endocytosis

Question 18

A cell actively transports $$Ca^{2+}$$ ions out of the cytoplasm. Where is the concentration of $$Ca^{2+}$$ higher?

Accepted Answer

Outside the cell

Question 19

Which of the following best explains why the formation of a simple lipid bilayer was not sufficient for the origin of life?

Accepted Answer

A bilayer alone cannot maintain selective permeability or perform complex functions without embedded proteins.

Question 20

Which of the following statements about aquaporins is correct?

Accepted Answer

They are protein channels that facilitate rapid water movement across the membrane.

Membrane Structure and Function: The Working Cell

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