Question 1

Which of the following best explains why the plasma membrane is described as a 'selectively permeable barrier'?

Accepted Answer

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

Question 2

A red blood cell is placed in a solution and swells until it bursts. Which type of solution was the cell placed in, and what is the underlying mechanism?

Accepted Answer

Hypotonic; water moved into the cell by osmosis.

Question 3

Which of the following best describes the function of the sodium-potassium pump ($$\mathrm{Na^+/K^+}-$$ATPase) in animal cells?

Accepted Answer

It uses ATP to move sodium ions out of the cell and potassium ions into the cell, maintaining an electrochemical gradient.

Question 4

Which of the following is a correct comparison between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus and membrane-bound organelles, while prokaryotic cells do not.

Question 5

A scientist observes that a certain enzyme-catalyzed reaction proceeds much faster in the presence of a molecule that binds to a site other than the active site. What is the most likely explanation?

Accepted Answer

The molecule is an allosteric activator, increasing enzyme activity by stabilizing the active form.

Question 6

Which of the following best describes the process of endocytosis?

Accepted Answer

The cell imports large molecules by engulfing them in vesicles formed from the plasma membrane.

Question 7

Which statement about the fluid mosaic model of the plasma membrane is correct?

Accepted Answer

Proteins and lipids can move laterally within the layer, contributing to membrane fluidity.

Question 8

A cell is placed in a solution containing a high concentration of glucose. Over time, glucose enters the cell through a membrane protein, but no ATP is used. What type of transport is this?

Accepted Answer

Facilitated diffusion

Question 9

Which of the following best explains how ATP hydrolysis can drive an endergonic reaction in a cell?

Accepted Answer

ATP hydrolysis is coupled to the endergonic reaction, so the overall $$\Delta G$$ for the combined process is negative.

Question 10

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The final product of a pathway binds to an allosteric site on an earlier enzyme, decreasing its activity.

Question 11

Which of the following best describes the role of ribosomes in the cell?

Accepted Answer

They are the site of protein synthesis, translating mRNA into polypeptides.

Question 12

A mutation causes a cell to lack functional lysosomes. Which of the following would most likely result?

Accepted Answer

The cell would accumulate undigested macromolecules, leading to cellular damage.

Question 13

Which of the following best describes the difference between competitive and noncompetitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind to the active site, while noncompetitive inhibitors bind to a different site, changing the enzyme's shape.

Question 14

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

Accepted Answer

Providing structural support, enabling cell movement, and facilitating intracellular transport.

Question 15

Which of the following statements about signal transduction pathways is correct?

Accepted Answer

Signal transduction often involves a cascade of protein phosphorylation events, amplifying the original signal.

Question 16

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

It helps maintain membrane fluidity by preventing tight packing of phospholipids at low temperatures and restraining movement at high temperatures.

Question 17

A cell is exposed to a toxin that blocks the function of microtubules. Which process would be most directly affected?

Accepted Answer

Chromosome separation during mitosis.

Question 18

Which of the following best describes the difference between catabolic and anabolic pathways?

Accepted Answer

Catabolic pathways break down complex molecules to release energy, while anabolic pathways use energy to build complex molecules.

Question 19

Which of the following is true regarding the Second Law of Thermodynamics as it applies to living systems?

Accepted Answer

Living systems increase the entropy of the universe by releasing heat and waste products, even as they maintain local order.

General Biology: Cell Structure, Membranes, Communication, and Metabolism Study Guide

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