Question 1

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

Accepted Answer

A double layer of phospholipids with proteins embedded throughout, allowing for flexibility and diverse functions.

Question 2

Why is the plasma membrane described as selectively permeable?

Accepted Answer

It regulates the movement of certain substances in and out of the cell based on size, charge, and polarity.

Question 3

Which of the following molecules would most easily diffuse across a plasma membrane without the help of a transport protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

A cell is placed in a solution and water moves into the cell, causing it to swell. What type of solution is the cell in?

Accepted Answer

Hypotonic

Question 5

Which process requires the cell to expend energy in the form of ATP?

Accepted Answer

Active transport

Question 6

A freshwater Paramecium uses contractile vacuoles to expel water. Why is this necessary?

Accepted Answer

The pond water is hypotonic to the Paramecium, causing water to enter the cell by osmosis.

Question 7

Which of the following best explains why facilitated diffusion does not require energy?

Accepted Answer

Molecules move down their concentration gradient with the help of transport proteins.

Question 8

What is the main function of aquaporins in the plasma membrane?

Accepted Answer

To facilitate the rapid diffusion of water molecules.

Question 9

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

Accepted Answer

Outside the cell

Question 10

Which of the following is an example of receptor-mediated endocytosis?

Accepted Answer

A cell taking in cholesterol by binding LDL particles to specific receptors.

Question 11

Which of the following statements about membrane proteins is correct?

Accepted Answer

Membrane proteins can function as enzymes, receptors, transporters, or attachment sites.

Question 12

A red blood cell is placed in a 2% NaCl solution. What will happen to the cell?

Accepted Answer

It will shrink as water leaves the cell.

Question 13

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

Accepted Answer

They act as ID tags that may be recognized by other cells.

Question 14

Which of the following scenarios best illustrates osmoregulation in bull sharks?

Accepted Answer

Bull sharks use their kidneys and rectal gland to excrete excess water and conserve salts when in freshwater.

Question 15

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

Accepted Answer

Synthesizing DNA

Question 16

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

Accepted Answer

Membranes also require embedded proteins to regulate the movement of substances.

Question 17

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

Accepted Answer

Increasing the temperature

Question 18

Which of the following is true about exocytosis?

Accepted Answer

It is used to export bulky molecules such as proteins or polysaccharides.

Question 19

A solution contains 0.5% sucrose on one side of a membrane and 2% sucrose on the other. The membrane is not permeable to sucrose. In which direction will water move?

Accepted Answer

From the 0.5% sucrose solution to the 2% sucrose solution

Question 20

Which of the following equations best represents the movement of molecules during passive transport?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Chapter 5: The Working Cell – Membrane Structure, Function, and Transport

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