Question 1

Which statement best describes the difference between catabolic and anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down large molecules into smaller ones and release energy, while anabolic pathways use energy to build complex molecules from simpler ones.

Question 2

A chemical reaction has a negative change in enthalpy ($$\Delta H  0). $$According to the Gibbs free energy equation $$\Delta G = \Delta H - T\Delta S$$, what can be concluded about the spontaneity of the reaction at high temperatures?

Accepted Answer

The reaction will be spontaneous at high temperatures.

Question 3

Which of the following best explains why ATP has a high potential energy?

Accepted Answer

ATP contains three phosphate groups with clustered negative charges that repel each other, making the bonds unstable and high in potential energy.

Question 4

During a redox reaction, which of the following statements is true?

Accepted Answer

Oxidation is the loss of electrons (often accompanied by loss of H), and reduction is the gain of electrons (often accompanied by gain of H).

Question 5

Which of the following is a direct result of the first law of thermodynamics in biological systems?

Accepted Answer

Energy in cells is conserved and can only be transferred or transformed, not created or destroyed.

Question 6

A researcher increases the temperature and concentration of reactants in a chemical reaction. What is the expected effect on the reaction rate, and why?

Accepted Answer

The reaction rate will increase because both higher temperature and concentration increase the frequency and energy of collisions between reactant molecules.

Question 7

Which of the following best describes how enzymes lower the activation energy of a reaction?

Accepted Answer

Enzymes bring substrates together in precise orientation and stabilize the transition state through interactions with active site R-groups.

Question 8

Which of the following is an example of competitive inhibition in enzyme regulation?

Accepted Answer

A molecule binds to the enzyme's active site, preventing the substrate from binding.

Question 9

Why do enzyme-catalyzed reactions show saturation kinetics at high substrate concentrations?

Accepted Answer

All available enzyme molecules are occupied, so the reaction rate cannot increase further even if more substrate is added.

Question 10

Which of the following statements about feedback inhibition in metabolic pathways is correct?

Accepted Answer

Feedback inhibition occurs when the final product of a pathway inhibits an enzyme earlier in the pathway, preventing overproduction.

Question 11

Which equation correctly represents the standard free-energy change for a chemical reaction?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 12

Which of the following is true regarding the effect of pH and temperature on enzyme activity?

Accepted Answer

Each enzyme has an optimal pH and temperature at which its activity is highest; deviations can alter enzyme shape and reduce activity.

Question 13

Which molecule acts as an electron carrier by accepting two electrons and one proton to form NADH?

Accepted Answer

NAD+

Question 14

What is the role of phosphorylation in enzyme regulation?

Accepted Answer

Phosphorylation is a reversible modification that can activate or deactivate enzymes by changing their shape.

Question 15

Which of the following is NOT a way that enzymes can be regulated?

Accepted Answer

Changing the DNA sequence of the enzyme after translation

Question 16

In a metabolic pathway, what is the consequence if the final product accumulates in high concentration?

Accepted Answer

The final product inhibits an earlier enzyme in the pathway, reducing further production (feedback inhibition).

Question 17

Which of the following statements about enzyme cofactors is correct?

Accepted Answer

Cofactors can be inorganic ions that reversibly interact with enzymes and are essential for enzyme function.

Question 18

Which of the following best describes the induced fit model of enzyme action?

Accepted Answer

The enzyme undergoes a conformational change when substrates bind, optimizing the fit and facilitating the reaction.

Question 19

Which of the following is a correct statement about metabolic pathway evolution according to the Horowitz model?

Accepted Answer

Enzymes evolve to produce new substrates when existing substrates decline, leading to the development of multistep pathways.

Chapter 8: Energy and Enzymes – An Introduction to Metabolism (General Biology Study Notes)

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