Question 1

Which statement best describes the relationship between the first and second laws of thermodynamics as they apply to biological systems?

Accepted Answer

The first law states that energy is conserved, and the second law states that every energy transfer increases the disorder (entropy) of the universe.

Question 2

Which of the following best explains why ATP hydrolysis is often coupled to unfavorable reactions in cells?

Accepted Answer

ATP hydrolysis releases energy, which can be used to drive endergonic reactions by coupling them, making the overall process exergonic.

Question 3

A reaction has a positive $$\Delta G$$ under cellular conditions. Which of the following is most likely to occur?

Accepted Answer

The reaction will require energy input, possibly from ATP hydrolysis, to proceed.

Question 4

Which of the following best describes the role of enzymes in metabolic reactions?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed faster without changing the overall $$\Delta G.$$

Question 5

Which of the following is a correct application of the Law of Conservation of Matter to cellular respiration?

Accepted Answer

The total number of atoms in the reactants equals the total number of atoms in the products.

Question 6

During glycolysis, which step is most directly responsible for the net production of ATP?

Accepted Answer

The substrate-level phosphorylation of ADP to ATP during the conversion of phosphoenolpyruvate to pyruvate.

Question 7

Which of the following best explains why oxygen is considered the ultimate electron acceptor in aerobic respiration?

Accepted Answer

Oxygen has the highest reduction potential in the electron transport chain, allowing it to accept electrons and form water.

Question 8

Which of the following statements about the citric acid cycle is correct?

Accepted Answer

The citric acid cycle generates NADH and FADH$$_2$$, which donate electrons to the electron transport chain.

Question 9

Which of the following best describes the role of the electron transport chain (ETC) in cellular respiration?

Accepted Answer

The ETC uses the energy from electrons to pump protons across the mitochondrial membrane, creating a gradient used for ATP synthesis.

Question 10

Which of the following best explains why the coupling of oxidation and reduction reactions is essential in metabolism?

Accepted Answer

It enables the transfer of energy through electron carriers, facilitating ATP production.

Question 11

A mutation causes a defect in Complex IV of the electron transport chain. Which of the following is the most likely consequence?

Accepted Answer

Oxygen will not be reduced to water, causing a backup of electrons and decreased ATP synthesis.

Question 12

Which of the following best describes substrate-level phosphorylation?

Accepted Answer

ATP is produced directly by transferring a phosphate group from a substrate to ADP.

Question 13

Which of the following is a major reason why glycolysis is considered an ancient metabolic pathway?

Accepted Answer

It occurs in the cytoplasm and does not require membrane-bound organelles or oxygen.

Question 14

Which of the following best explains the importance of compartmentalization in cellular metabolism?

Accepted Answer

It separates incompatible reactions and allows for regulation and efficiency of metabolic pathways.

Question 15

Which of the following statements about redox reactions in the electron transport chain is correct?

Accepted Answer

Electrons move from carriers with lower to higher reduction potential, releasing energy.

Question 16

Which of the following best describes the role of NADH in cellular respiration?

Accepted Answer

NADH donates electrons to the electron transport chain, helping to generate a proton gradient for ATP synthesis.

Question 17

Which of the following best explains why the oxidation of glucose is highly exergonic?

Accepted Answer

The products (CO$$_2$$ and H$$_2O) $$are at a much lower free energy than the reactants (glucose and O$$_2$$), resulting in a large negative $$\Delta G.$$

Question 18

Which of the following is the best explanation for why ATP synthase requires a proton gradient to function?

Accepted Answer

The proton gradient provides the energy needed to drive the phosphorylation of ADP to ATP as protons flow through ATP synthase.

Question 19

Which of the following best describes the fate of pyruvate in the presence of oxygen?

Accepted Answer

Pyruvate is transported into the mitochondria and converted to acetyl-CoA, which enters the citric acid cycle.

Question 20

Which of the following best explains the importance of the 'decision point' at pyruvate in cellular metabolism?

Accepted Answer

Pyruvate can be directed toward fermentation or aerobic respiration depending on oxygen availability, allowing cells to adapt to changing conditions.

Central Metabolism, Thermodynamics, and Cellular Respiration Study Guide

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