Q: A chemical reaction has a negative free-energy change ($\Delta G < 0$). What does this indicate about the reaction?

The reaction is exergonic and will occur spontaneously.

Q: Which of the following best distinguishes between exergonic and endergonic reactions?

Exergonic reactions release energy ($\Delta G 0$).

Question 1

Which statement best describes the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 2

A chemical reaction has a negative free-energy change ($\Delta G < 0$). What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and will occur spontaneously.

Question 3

Which of the following best distinguishes between exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions release energy ($\Delta G < 0$); endergonic reactions require energy input ($\Delta G > 0$).

Question 4

How does ATP typically power cellular work?

Accepted Answer

By coupling the hydrolysis of ATP (an exergonic reaction) to endergonic reactions, making them energetically favorable.

Question 5

Which of the following is NOT a main kind of cellular work powered by ATP?

Accepted Answer

Photosynthetic work, such as absorbing sunlight directly.

Question 6

What is the relationship between ATP and ADP in cellular metabolism?

Accepted Answer

ATP is formed by the addition of a phosphate group to ADP, storing energy; hydrolysis of ATP to ADP releases energy for cellular work.

Question 7

Why do enzymes dramatically increase the rate of biological reactions?

Accepted Answer

They lower the activation energy barrier ($E_a$) required for the reaction to proceed.

Question 8

Which property of enzymes allows them to be highly specific for their substrates?

Accepted Answer

The unique three-dimensional structure of their active site.

Question 9

A patient has a fever of 41°C. How might this affect the activity of most human enzymes?

Accepted Answer

Enzyme activity will decrease because the enzyme may denature at high temperatures.

Question 10

Which scenario best illustrates the effect of a competitive inhibitor on enzyme activity?

Accepted Answer

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

Question 11

How does feedback inhibition regulate metabolic pathways?

Accepted Answer

The end product of a pathway acts as an allosteric inhibitor of an enzyme early in the pathway, preventing overproduction.

Question 12

Which of the following best describes allosteric regulation of an enzyme?

Accepted Answer

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

Question 13

A cell needs to tightly regulate the production of isoleucine. Which mechanism is most likely used?

Accepted Answer

Isoleucine acts as a feedback inhibitor, binding to the first enzyme in its biosynthetic pathway.

Question 14

Which of the following is an example of coupling an exergonic and an endergonic reaction in a cell?

Accepted Answer

Using the energy released from ATP hydrolysis ($\Delta G < 0$) to drive the synthesis of glutamine from glutamate and ammonia ($\Delta G > 0$).

Question 15

Which of the following would most likely increase the rate of an enzyme-catalyzed reaction that is currently below its optimal temperature?

Accepted Answer

Increasing the temperature to the enzyme's optimal range.

Question 16

A metabolic pathway is regulated by the end product binding to an enzyme at a site other than the active site. What is this type of regulation called?

Accepted Answer

Allosteric inhibition

Question 17

Which of the following best explains why enzymes do not alter the $\Delta G$ of a reaction?

Accepted Answer

Enzymes lower the activation energy but do not affect the overall free energy change.

Question 18

A scientist adds a molecule that binds to an enzyme and decreases its activity, but the molecule does not bind to the active site. What is this molecule called?

Accepted Answer

Allosteric inhibitor

Question 19

Which of the following is a real-world example of feedback inhibition in human metabolism?

Accepted Answer

ATP inhibits phosphofructokinase in glycolysis when cellular energy is high.

Question 20

If a cell's environment becomes more acidic, how might this affect enzyme activity?

Accepted Answer

Enzyme activity may decrease because the enzyme's structure and active site can be altered by changes in pH.

Cellular Energy and Enzyme Function: Study Notes

Study Guide - Practice Questions

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