Question 1

Which of the following best explains how cholesterol affects the fluidity of animal cell membranes at low temperatures?

Accepted Answer

Cholesterol increases membrane fluidity by preventing fatty acid tails from packing tightly together.

Question 2

A cell is placed in a solution containing a high concentration of glucose. Glucose is a large polar molecule. Which transport mechanism will most likely be used for glucose to enter the cell?

Accepted Answer

Facilitated diffusion through a specific transporter protein.

Question 3

Which of the following statements about the second law of thermodynamics is correct?

Accepted Answer

The entropy of the universe always increases in a spontaneous process.

Question 4

Given the following reaction: $A ightarrow B$, with $G_{	ext{initial}} = 10\ \mathrm{kJ/mol}$ and $G_{	ext{final}} = 2\ \mathrm{kJ/mol}$, what is $\Delta G$ and is the reaction spontaneous?

Accepted Answer

$\Delta G = -8\ \mathrm{kJ/mol}$; the reaction is spontaneous.

Question 5

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

Accepted Answer

ATP hydrolysis releases energy that is coupled to the endergonic reaction, making the overall process exergonic.

Question 6

A scientist adds a molecule to an enzyme-catalyzed reaction. The molecule binds to the active site, preventing substrate binding. What type of inhibitor is this?

Accepted Answer

Competitive inhibitor

Question 7

During glycolysis, which enzyme is responsible for transferring a phosphate group from ATP to glucose?

Accepted Answer

Kinase

Question 8

In the electron transport chain of aerobic respiration, what is the final electron acceptor, and why is it essential?

Accepted Answer

Oxygen; it allows the chain to continue by accepting electrons and forming water.

Question 9

Which of the following best explains why controlled energy release during cellular respiration is important for living organisms?

Accepted Answer

It allows cells to capture energy efficiently in the form of ATP rather than losing it all as heat.

Question 10

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation regenerates NAD+ by transferring electrons to an organic molecule, allowing glycolysis to continue in the absence of oxygen.

Question 11

A metabolic pathway involves the following reaction: $\mathrm{NAD}^+ + 2e^- + 2H^+ \rightarrow \mathrm{NADH} + H^+$. In this reaction, which molecule is reduced and what is its role?

Accepted Answer

$\mathrm{NAD}^+$ is reduced; it acts as an electron carrier.

Question 12

Which of the following best describes the main function of the electron transport chain in mitochondria?

Accepted Answer

To create a proton gradient across the inner mitochondrial membrane, which drives ATP synthesis via chemiosmosis.

Question 13

Which of the following statements about substrate-level phosphorylation and oxidative phosphorylation is correct?

Accepted Answer

Substrate-level phosphorylation directly transfers a phosphate group to ADP from a phosphorylated intermediate, while oxidative phosphorylation uses a proton gradient to drive ATP synthesis.

Question 14

A patient is diagnosed with a genetic disorder that prevents the formation of functional voltage-gated ion channels in neurons. Which process would be most directly affected?

Accepted Answer

The ability of neurons to generate and propagate action potentials.

Question 15

Which of the following best describes the difference between catabolism and anabolism?

Accepted Answer

Catabolism breaks down molecules and releases energy; anabolism builds molecules and requires energy.

Question 16

In which part of a eukaryotic cell does glycolysis occur, and what is the net ATP gain per glucose molecule?

Accepted Answer

Cytoplasm; net gain of 2 ATP per glucose.

Question 17

A cell is exposed to a toxin that inhibits dehydrogenase enzymes. Which process would be most directly impaired?

Accepted Answer

The transfer of electrons to NAD+ and FAD during cellular respiration.

Question 18

During anaerobic respiration in some bacteria, which molecule can serve as the final electron acceptor instead of oxygen?

Accepted Answer

Nitrate ($\mathrm{NO}_3^-$)

Question 19

Which of the following best explains why unsaturated fatty acids increase membrane fluidity at low temperatures?

Accepted Answer

Their kinks prevent tight packing of phospholipids, allowing more movement.

Question 20

A metabolic pathway has the following steps: $A \xrightarrow{	ext{isomerase}} B \xrightarrow{	ext{dehydrogenase}} C$. If $A$ is converted to $B$ by isomerase, what is the role of the dehydrogenase in the next step?

Accepted Answer

It catalyzes the removal of electrons from $B$, transferring them to an electron carrier.

Cell Membranes, Thermodynamics, and Cellular Respiration: Study Guide

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