Question 1

Which of the following best explains why biological membranes are described as 'selectively permeable'?

Accepted Answer

They allow some substances to cross more easily than others due to the structure and composition of the lipid bilayer and embedded proteins.

Question 2

A researcher increases the proportion of unsaturated fatty acids in a cell membrane. What is the most likely effect on membrane fluidity and permeability?

Accepted Answer

Membrane fluidity will increase and permeability will increase because unsaturated tails prevent tight packing.

Question 3

Which of the following best describes the mechanism of the Na+/K+ pump?

Accepted Answer

It moves 3 Na+ ions out of the cell and 2 K+ ions into the cell using ATP hydrolysis.

Question 4

A cell is placed in a solution and begins to swell. Which of the following best describes the tonicity of the solution relative to the cell?

Accepted Answer

The solution is hypotonic to the cell.

Question 5

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It uses membrane proteins to move molecules down their concentration gradient without energy input.

Question 6

Which of the following best describes the function of the endomembrane system in eukaryotic cells?

Accepted Answer

It synthesizes, modifies, sorts, and transports proteins and lipids within the cell.

Question 7

A mutation causes a eukaryotic cell to lack functional lysosomes. Which of the following processes would be most directly affected?

Accepted Answer

Breakdown of macromolecules and cellular debris

Question 8

Which of the following is a key difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus containing DNA, while prokaryotic cells have DNA in a nucleoid region.

Question 9

Which of the following best describes the role of cadherins in animal cells?

Accepted Answer

They are adhesion molecules that mediate selective cell-cell recognition and tissue cohesiveness.

Question 10

A scientist observes that a certain membrane channel only opens in response to a specific voltage across the membrane. Which type of channel is this?

Accepted Answer

Voltage-gated channel

Question 11

Which of the following best explains why the addition of cholesterol to a membrane at high temperatures decreases membrane fluidity?

Accepted Answer

Cholesterol stabilizes the membrane by restricting the movement of phospholipids.

Question 12

Which of the following is true regarding signal transduction via G-protein-coupled receptors (GPCRs)?

Accepted Answer

Binding of a ligand to the receptor activates a G protein, which then activates downstream effectors.

Question 13

A cell is exposed to a signaling molecule that binds to an enzyme-linked receptor. Which of the following is most likely to occur next?

Accepted Answer

The receptor undergoes a conformational change and initiates a phosphorylation cascade.

Question 14

Which of the following best describes the function of tight junctions in animal cells?

Accepted Answer

They form a barrier that prevents the movement of substances between cells.

Question 15

A plant cell is placed in a solution with a lower solute concentration than its cytoplasm. What will happen to the cell?

Accepted Answer

Water will move into the cell, causing it to become turgid.

Question 16

Which of the following is a correct sequence of events in the endomembrane system for a secreted protein?

Accepted Answer

Rough ER → Golgi apparatus → vesicle → plasma membrane

Question 17

Which of the following best describes the process of receptor-mediated endocytosis?

Accepted Answer

The cell takes in specific molecules after they bind to receptors on the cell surface.

Question 18

A cell has a higher concentration of glucose outside than inside. Which transport mechanism is most likely responsible for the net movement of glucose into the cell?

Accepted Answer

Facilitated diffusion via a carrier protein such as GLUT-1

Question 19

Which of the following best explains the role of phosphorylation cascades in cell signaling?

Accepted Answer

They amplify the signal by activating multiple downstream proteins through sequential phosphorylation.

Question 20

A cell is exposed to a toxin that blocks all aquaporins. What is the most likely effect on the cell?

Accepted Answer

The cell will have reduced water permeability, impairing osmosis.

Membranes, Cell Structure, and Cell-Cell Interactions: Study Guide for Biology 161 Test 2

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