Question 1

Which of the following best explains why an enzyme increases the rate of a chemical reaction?

Accepted Answer

It lowers the activation energy ($$E_A) $$required to reach the transition state.

Question 2

A cell has abundant ATP and nutrients but is not growing. According to the study materials, which of the following is the most likely explanation?

Accepted Answer

The cell's metabolic demand for growth is low, so energy is used for maintenance instead.

Question 3

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzymes have active sites that bind specific substrates, allowing only certain reactions to occur.

Question 4

If a competitive inhibitor is added to an enzyme-catalyzed reaction, which of the following will occur?

Accepted Answer

The inhibitor will compete with the substrate for the active site, and increasing substrate concentration can overcome the inhibition.

Question 5

Which of the following best describes feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of the pathway inhibits an earlier enzyme, reducing further synthesis.

Question 6

A scientist observes that increasing substrate concentration no longer increases the rate of an enzyme-catalyzed reaction. What is the most likely explanation?

Accepted Answer

The enzyme is saturated; all active sites are occupied.

Question 7

Which of the following is a key difference between competitive and noncompetitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind the active site, while noncompetitive inhibitors bind elsewhere and change enzyme shape.

Question 8

Why do different tissues in an organism respond differently to the same nutrient supply?

Accepted Answer

They express different combinations of enzymes and have different metabolic demands.

Question 9

Which of the following best explains why the optimal temperature for enzyme activity differs between human enzymes and those from thermophilic bacteria?

Accepted Answer

Enzymes evolve to function best at the typical temperature of their environment.

Question 10

A metabolic pathway is regulated by allosteric inhibition. Which of the following is most likely to occur when the allosteric inhibitor is present?

Accepted Answer

The enzyme changes shape, reducing its activity even if substrate is abundant.

Question 11

Which of the following scenarios best illustrates the concept of metabolic demand?

Accepted Answer

A muscle cell increases ATP production during exercise to meet increased energy needs.

Question 12

Which of the following is NOT a way that cells regulate enzyme activity?

Accepted Answer

Changing the DNA sequence of the enzyme gene.

Question 13

A patient is exposed to a toxin that acts as a noncompetitive inhibitor of a key metabolic enzyme. What is the most likely effect on the enzyme's activity?

Accepted Answer

The enzyme's activity will decrease, and this cannot be overcome by increasing substrate concentration.

Question 14

Which of the following best describes the role of compartmentalization in metabolic regulation?

Accepted Answer

It allows cells to concentrate substrates and separate incompatible reactions in different organelles.

Question 15

A tissue in a growing pig increases in size after hemi-castration, as shown in the first image. Which of the following molecular explanations is most consistent with this observation?

Accepted Answer

The remaining tissue increases its metabolic capacity or demand to compensate for the loss.

Question 16

Which of the following equations correctly represents the relationship between free energy change and reaction spontaneity?

Accepted Answer

$$\Delta G \u003c 0$$ indicates a spontaneous reaction.

Question 17

A metabolic pathway is running at maximum rate, but the cell suddenly needs to increase product output. Which of the following is the most effective way for the cell to increase the pathway's flux?

Accepted Answer

Increase the abundance or activity of the pathway's enzymes.

Question 18

Which of the following best explains why metabolic regulation is necessary in cells?

Accepted Answer

To coordinate the use of resources and prevent wasteful synthesis when demand is low.

Metabolic Regulation and Enzyme Activity: Study Notes for General Biology

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