Question 1

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

Accepted Answer

Anabolic pathways consume energy to build complex molecules, while catabolic pathways release energy by breaking down complex molecules.

Question 2

According to the first law of thermodynamics, which of the following statements is correct?

Accepted Answer

Energy can be transferred and transformed, but it cannot be created or destroyed.

Question 3

A bear eats a fish and then runs, releasing heat and producing $$CO_2$$ and $$H_2O. $$Which law of thermodynamics does this scenario best illustrate?

Accepted Answer

Both the first and second laws of thermodynamics

Question 4

Which of the following equations correctly represents the change in Gibbs free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

$$\Delta G = G_{final} - G_{initial}$$

Question 5

Which of the following is true for an exergonic reaction?

Accepted Answer

$$\Delta G is $$negative and the reaction releases energy.

Question 6

In the context of ATP hydrolysis, why does phosphorylation of a substrate often result in a large change in free energy?

Accepted Answer

Phosphorylation adds three tightly packed negative charges, increasing repulsion and instability.

Question 7

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The active site of an enzyme has a unique shape and chemical environment that fits only specific substrates.

Question 8

Which of the following statements about enzyme-catalyzed reactions is correct?

Accepted Answer

Enzymes lower the activation energy but do not change the overall $$\Delta G of $$the reaction.

Question 9

A graph shows the rate of an enzyme-catalyzed reaction increasing with substrate concentration, then leveling off. What is the most likely explanation for the plateau?

Accepted Answer

All enzyme active sites are saturated with substrate, so adding more substrate does not increase the rate.

Question 10

Which of the following environmental changes is most likely to cause denaturation of an enzyme?

Accepted Answer

A drastic change in pH away from the enzyme's optimal pH.

Question 11

A patient is given a drug that acts as a competitive inhibitor for a key metabolic enzyme. Which of the following would most likely overcome the inhibition?

Accepted Answer

Increasing the concentration of the substrate.

Question 12

Which of the following best describes the effect of a noncompetitive inhibitor on an enzyme?

Accepted Answer

It binds to a site other than the active site, causing a conformational change that reduces enzyme activity.

Question 13

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

Accepted Answer

The final product of a pathway inhibits an earlier enzyme in the pathway.

Question 14

Which of the following statements about cofactors is correct?

Accepted Answer

Cofactors can be either inorganic ions or organic molecules called coenzymes.

Question 15

A graph shows the rate of reaction for an enzyme at different temperatures. The rate increases up to 37°C, then rapidly decreases. What is the most likely explanation for the decrease above 37°C?

Accepted Answer

The enzyme is being denatured at higher temperatures.

Question 16

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP hydrolysis releases energy that can be used to drive endergonic reactions.

Question 17

Which of the following scenarios best illustrates energy coupling in a cell?

Accepted Answer

A catabolic reaction releases energy, which is then used to drive an anabolic reaction.

Question 18

If a metabolic pathway is regulated by feedback inhibition, what would happen if the end product is removed from the system?

Accepted Answer

The pathway would continue to operate, producing more end product.

Question 19

Which of the following best describes the role of the active site in an enzyme?

Accepted Answer

It is a region where the substrate binds and the reaction is catalyzed.

Question 20

A scientist observes that increasing substrate concentration does not increase the rate of reaction in the presence of a noncompetitive inhibitor. What is the best explanation for this observation?

Accepted Answer

The inhibitor binds to a different site, causing a conformational change that reduces enzyme activity regardless of substrate concentration.

Introduction to Metabolism: Energy, Enzymes, and Regulation

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