Question 1

Which of the following statements best describes an exergonic reaction?

Accepted Answer

The products have lower free energy than the reactants, and energy is released.

Question 2

A scientist observes that the reaction $$ 	ext{Glucose} + 	ext{Phosphate} ightarrow 	ext{Glucose-6-phosphate} $$ does not occur spontaneously in a test tube. However, in a living cell, this reaction proceeds rapidly. Which process explains this observation?

Accepted Answer

The cell couples the reaction to ATP hydrolysis, making the overall process exergonic.

Question 3

Which of the following best explains why enzymes do not alter the overall free energy change ($$ \Delta G ) of a $$reaction?

Accepted Answer

Enzymes lower the activation energy but do not change the energy difference between reactants and products.

Question 4

A patient is given a drug that binds to the active site of an enzyme, preventing the substrate from binding. What type of inhibition is this?

Accepted Answer

Competitive inhibition

Question 5

Which of the following scenarios is an example of allosteric regulation?

Accepted Answer

A molecule binds to a site other than the active site, causing a conformational change that alters enzyme activity.

Question 6

If the tertiary structure of an enzyme is disrupted by heat, what is the most likely consequence?

Accepted Answer

The active site may be altered, reducing or eliminating enzyme activity.

Question 7

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

Accepted Answer

The end product of the pathway inhibits an enzyme involved early in the pathway.

Question 8

A cell is found to have very low ATP levels. What is the most likely effect on ATP-producing metabolic pathways?

Accepted Answer

Inhibition of enzymes in ATP-producing pathways will be relieved, increasing ATP production.

Question 9

Which of the following equations correctly represents the hydrolysis of ATP?

Accepted Answer

$$ \mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} $$

Question 10

A researcher adds a competitive inhibitor to an enzyme-catalyzed reaction. Which of the following changes would most likely restore the original reaction rate?

Accepted Answer

Increasing the concentration of the substrate.

Question 11

Which of the following statements about the coupling of ATP hydrolysis to endergonic reactions is correct?

Accepted Answer

ATP hydrolysis is exergonic and can drive endergonic reactions by making the overall $$ \Delta G $$ negative.

Question 12

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

Accepted Answer

The enzyme's active site has a unique 3D shape that fits only specific substrates.

Question 13

A mutation changes a single amino acid in the primary structure of an enzyme. Which of the following outcomes is most likely?

Accepted Answer

The enzyme's 3D structure may be altered, potentially affecting its function.

Question 14

Which of the following is true regarding the activation energy ($$ E_a ) of a $$reaction?

Accepted Answer

Enzymes lower $$ E_a $$, allowing reactions to proceed more rapidly.

Question 15

A metabolic pathway produces ATP. When ATP levels are high, the pathway slows down. What is the most likely mechanism for this regulation?

Accepted Answer

ATP acts as an allosteric inhibitor for an enzyme early in the pathway.

Question 16

Which of the following best describes an endergonic reaction?

Accepted Answer

The products have higher free energy than the reactants, and energy is absorbed.

Question 17

A cell is exposed to a toxin that disrupts allosteric sites on enzymes. Which of the following is a likely consequence?

Accepted Answer

Enzymes will lose the ability to be regulated by molecules that bind outside the active site.

Question 18

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

Accepted Answer

Changing the DNA sequence of the enzyme after it is made

Question 19

A metabolic pathway is responsible for synthesizing a vital amino acid. If the final product of this pathway accumulates and inhibits the first enzyme in the pathway, what is this an example of?

Accepted Answer

Feedback inhibition

Question 20

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

Accepted Answer

ATP stores energy in its phosphate bonds, which can be released to drive endergonic reactions when hydrolyzed.

Energy, Enzymes, and Regulation in Cellular Metabolism

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