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 at room temperature?

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 cytoplasm?

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 substances down their concentration gradient without energy input.

Question 6

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

Cholesterol stabilizes membrane fluidity by preventing extremes of rigidity or fluidity.

Question 7

A mutation causes a cell to lack functional aquaporins. Which process would be most directly affected?

Accepted Answer

Facilitated diffusion of water across the membrane.

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 organelle is primarily responsible for modifying, sorting, and packaging proteins for secretion or delivery to other organelles?

Accepted Answer

Golgi apparatus

Question 10

A white blood cell engulfs a bacterium by surrounding it with its plasma membrane, forming a vesicle. This process is best described as:

Accepted Answer

Phagocytosis

Question 11

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

Accepted Answer

They form a seal that prevents the passage of substances between cells.

Question 12

Which statement about signal transduction via G-protein-coupled receptors (GPCRs) is correct?

Accepted Answer

GPCRs activate G-proteins, which then trigger production of second messengers inside the cell.

Question 13

A scientist observes that a certain animal cell type expresses high levels of cadherins. What is the most likely function of these proteins?

Accepted Answer

Facilitating selective adhesion between similar cells during tissue formation.

Question 14

Which of the following best describes the process of signal amplification in cell signaling?

Accepted Answer

A single signaling molecule leads to the activation of many intracellular molecules, increasing the strength of the signal.

Question 15

Which of the following is a function of the cytoskeleton in eukaryotic cells?

Accepted Answer

Providing structural support and enabling vesicle movement within the cell.

Question 16

A cell is exposed to a toxin that inhibits all ATP production. Which transport process would be most directly affected?

Accepted Answer

Active transport of Na+ and K+ ions.

Question 17

Which of the following best describes the function of the extracellular matrix (ECM) in animal cells?

Accepted Answer

It provides structural support and mediates cell signaling and adhesion.

Question 18

A cell receives a signal molecule that binds to an enzyme-linked receptor. What is the most likely immediate result?

Accepted Answer

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

Question 19

Which of the following best explains why the Na+/K+ pump is essential for maintaining the electrochemical gradient across the plasma membrane?

Accepted Answer

It actively transports Na+ out and K+ in, creating a charge difference and concentration gradient across the membrane.

Question 20

A plant cell is placed in a solution with a lower solute concentration than its cytoplasm. Which equation best describes the net movement of water, and what is the expected outcome for the cell?

Accepted Answer

Water moves into the cell, increasing turgor pressure. $\Delta \Psi = \Psi_{outside} - \Psi_{inside} > 0$

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

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