Q: Which of the following equations correctly represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation?

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[\text{ion}]_{\text{outside}}}{[\text{ion}]_{\text{inside}}} \right)$$

Question 1

Which of the following best describes the amphipathic nature of phospholipids in the plasma membrane?

Accepted Answer

They have both a hydrophilic phosphate-containing head and two hydrophobic fatty acid tails.

Question 2

A patient is diagnosed with a genetic disorder that affects the formation of desmosomes. Which tissue is most likely to be affected, and what is the expected consequence?

Accepted Answer

Epidermal tissue; increased risk of skin tearing under mechanical stress.

Question 3

Which type of cell junction allows for direct communication between adjacent cells by permitting the passage of ions and small molecules?

Accepted Answer

Gap junction

Question 4

Which of the following best explains why ions such as $$\mathrm{Na^+}$$ and $$\mathrm{K^+}$$ require membrane channels to cross the plasma membrane?

Accepted Answer

Ions are charged and cannot pass through the hydrophobic core of the lipid bilayer.

Question 5

A researcher adds a chemical that blocks ATP synthesis in a cell. Which membrane transport process will be most directly affected?

Accepted Answer

Primary active transport

Question 6

Which of the following is a key advantage of receptor-mediated endocytosis over pinocytosis?

Accepted Answer

It allows the cell to selectively take up specific molecules from the extracellular fluid.

Question 7

Which of the following best describes the function of tight junctions in epithelial tissue?

Accepted Answer

They form a permeability barrier that prevents substances from passing between adjacent cells.

Question 8

A cell is placed in a solution with a higher concentration of non-penetrating solutes than its cytoplasm. What will happen to the cell, and which process is responsible?

Accepted Answer

The cell will shrink due to osmosis.

Question 9

Which of the following best describes the role of G-protein coupled receptors (GPCRs) in cell signaling?

Accepted Answer

They activate intracellular second messengers in response to ligand binding.

Question 10

Which of the following equations correctly represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 11

Which of the following scenarios best illustrates secondary active transport?

Accepted Answer

A sodium-glucose symporter uses the sodium gradient established by the Na+/K+ ATPase to transport glucose into the cell.

Question 12

Which of the following best explains why the movement of $$\mathrm{K^+}$$ out of a neuron makes the membrane potential more negative?

Accepted Answer

Positive charge leaves the cell, increasing the negative charge inside relative to outside.

Question 13

Which of the following is a characteristic of facilitated diffusion?

Accepted Answer

It requires a membrane protein but does not require ATP.

Question 14

A mutation causes a cell to lack hemidesmosomes. Which function would be most directly impaired?

Accepted Answer

Anchoring the cell to the underlying extracellular matrix.

Question 15

Which of the following best describes the difference between primary and secondary active transport?

Accepted Answer

Primary active transport directly uses ATP, while secondary active transport uses the energy stored in an ion gradient.

Question 16

Which of the following is true regarding the distribution of major cations in body fluid compartments?

Accepted Answer

Potassium ($$\mathrm{K^+}) is $$the major intracellular cation, while sodium ($$\mathrm{Na^+}) is $$the major extracellular cation.

Question 17

Which of the following best describes the function of enzyme-linked membrane receptors?

Accepted Answer

They activate intracellular enzymes, often through phosphorylation, upon ligand binding.

Question 18

A cell is exposed to a toxin that locks all voltage-gated sodium channels in the closed state. What is the most likely effect on the cell's ability to generate an action potential?

Accepted Answer

The cell will be unable to depolarize and generate an action potential.

Question 19

Which of the following best explains why the osmotic concentration of body fluid compartments is the same, even though their ionic compositions differ?

Accepted Answer

Water moves freely across cell membranes, balancing osmotic pressure between compartments.

Cellular Level of Organization: Review of Cell Membrane Features

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