Q: If the hydrolysis of ATP to ADP and $P_i$ releases $\Delta G = -7.3$ kcal/mol, what is the net $\Delta G$ for a coupled reaction that requires $+5$ kcal/mol?

$$\Delta G = -2.3 \text{ kcal/mol}$$

Question 1

Which of the following best describes a catabolic pathway in cellular metabolism?

Accepted Answer

A pathway that releases energy by breaking down complex molecules into simpler compounds.

Question 2

A diver climbs up a ladder to a diving platform, increasing her potential energy. Which type of energy transformation occurs as she jumps off and enters the water?

Accepted Answer

Potential energy is converted to kinetic energy.

Question 3

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

Accepted Answer

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

Question 4

Which equation correctly represents the change in free energy ($\Delta G$) for a chemical reaction?

Accepted Answer

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

Question 5

A reaction has a $\Delta G$ of $-10$ kcal/mol. What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and will proceed spontaneously.

Question 6

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

Accepted Answer

ATP contains high-energy phosphate bonds that release energy when hydrolyzed.

Question 7

If the hydrolysis of ATP to ADP and $P_i$ releases $\Delta G = -7.3$ kcal/mol, what is the net $\Delta G$ for a coupled reaction that requires $+5$ kcal/mol?

Accepted Answer

$$\Delta G = -2.3 	ext{ kcal/mol}$$

Question 8

Which of the following statements about enzymes is TRUE?

Accepted Answer

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

Question 9

A scientist is studying an enzyme that works best at pH 2. What is the most likely location of this enzyme in the human body?

Accepted Answer

Stomach

Question 10

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

Accepted Answer

The enzyme changes shape slightly to bind the substrate more tightly.

Question 11

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

Accepted Answer

Competitive inhibition

Question 12

Which of the following is a real-life example of feedback inhibition?

Accepted Answer

The end product of a metabolic pathway inhibits an enzyme that acts early in the pathway.

Question 13

Which of the following best explains why increasing substrate concentration can overcome competitive inhibition but not noncompetitive inhibition?

Accepted Answer

Competitive inhibitors bind to the active site, so more substrate can outcompete them; noncompetitive inhibitors bind elsewhere and change enzyme shape.

Question 14

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

Accepted Answer

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

Question 15

Which of the following scenarios best illustrates the second law of thermodynamics in a biological system?

Accepted Answer

A cell uses energy from ATP to build complex molecules, increasing order locally but releasing heat to the environment.

Question 16

Which of the following is TRUE about the equilibrium of a chemical reaction in a living cell?

Accepted Answer

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction.

Question 17

A researcher finds that an enzyme's activity increases as more substrate is added, but then levels off even as substrate continues to increase. What is the most likely explanation?

Accepted Answer

All active sites of the enzyme molecules are occupied (enzyme saturation).

Question 18

Which of the following best describes cooperativity in enzyme regulation?

Accepted Answer

A substrate binding to one active site increases the activity at other active sites.

Question 19

A mutation causes an enzyme to lose its optimal temperature range, resulting in decreased activity at human body temperature. Which of the following is the most likely consequence?

Accepted Answer

The enzyme will be less effective at catalyzing its reaction in the human body.

Question 20

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

Accepted Answer

The shape and chemical environment of the active site are complementary to the substrate.

Introduction to Metabolism and Enzyme Function: General Biology Study Notes (chapter 6)

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