Question 1

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

Accepted Answer

A double layer of phospholipids with embedded proteins and cholesterol, where components can move laterally

Question 2

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

Accepted Answer

To increase the stiffness and stability of the membrane

Question 3

Which of the following molecules can most easily diffuse directly through the plasma membrane by simple diffusion?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

A cell is placed in a solution with a higher concentration of solutes than inside the cell. What will happen to the cell due to osmosis?

Accepted Answer

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

Question 5

Which of the following best explains why facilitated diffusion is necessary for glucose transport across the plasma membrane?

Accepted Answer

Glucose is a large, polar molecule that cannot cross the hydrophobic core of the membrane without assistance

Question 6

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It uses ATP to move 3 sodium ions out of the cell and 2 potassium ions into the cell

Question 7

A nerve cell has a resting membrane potential of $$-70\ \mathrm{mV}. $$Which ion is primarily responsible for establishing this potential, and why?

Accepted Answer

Potassium ($$K^+$$), because it diffuses out of the cell, leaving behind a negative charge

Question 8

Which of the following is a function of integral membrane proteins?

Accepted Answer

Acting as enzymes, transporters, and receptors

Question 9

A patient is given a drug that blocks all ATP production in their cells. Which of the following transport processes would be most directly affected?

Accepted Answer

Primary active transport of sodium and potassium

Question 10

Which of the following best describes the difference between ionotropic and metabotropic receptors?

Accepted Answer

Ionotropic receptors are ligand-gated ion channels that mediate rapid responses, while metabotropic receptors activate second messenger systems and mediate slower, prolonged responses

Question 11

Which of the following scenarios best illustrates secondary active transport?

Accepted Answer

A sodium-glucose cotransporter uses the sodium gradient established by the sodium-potassium pump to bring glucose into the cell

Question 12

Which of the following is true regarding the selective permeability of the plasma membrane?

Accepted Answer

Lipid-soluble molecules can cross unassisted, while water-soluble and large molecules require transport proteins

Question 13

A cell is exposed to a toxin that permanently opens all potassium ($$K^+) $$channels. What is the most likely effect on the resting membrane potential?

Accepted Answer

The membrane potential would become more negative (hyperpolarized)

Question 14

Which of the following best explains the role of G-proteins in cell signaling?

Accepted Answer

They act as intermediaries, relaying signals from membrane receptors to intracellular second messengers

Question 15

Which of the following is an example of contact signaling?

Accepted Answer

Two immune cells recognizing each other by their unique surface membrane receptors

Question 16

Which of the following factors would increase the rate of simple diffusion across the plasma membrane?

Accepted Answer

Increasing the concentration gradient

Question 17

Which of the following best describes the function of aquaporins in the plasma membrane?

Accepted Answer

They allow water to move rapidly across the membrane by facilitated diffusion

Question 18

A mutation causes a cell to lack peripheral proteins. Which of the following cellular functions would be most directly affected?

Accepted Answer

Cell-to-cell connections and shape changes during cell division

Question 19

Which of the following best explains why the inside of a resting cell is negative relative to the outside?

Accepted Answer

Potassium ions diffuse out of the cell, leaving behind negatively charged proteins and other anions

Question 20

Which of the following is a real-life example of a disease or condition resulting from defective membrane transport proteins?

Accepted Answer

Cystic fibrosis, caused by a mutation in the CFTR chloride channel

Membrane Transport and the Plasma Membrane: Structure and Function

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