Question 1

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

Accepted Answer

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

Question 2

A cell performs an endergonic reaction by coupling it to ATP hydrolysis. Which of the following best explains why this is possible?

Accepted Answer

The free energy released from ATP hydrolysis ($$ \Delta G  0 $$ when the two are coupled.

Question 3

Which of the following equations correctly represents the change in free energy for a reaction?

Accepted Answer

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

Question 4

Which of the following best describes a spontaneous reaction in terms of free energy?

Accepted Answer

A reaction with $$ \Delta G \u003c 0 $$ that can proceed without energy input.

Question 5

Which of the following is an example of how ATP hydrolysis is coupled to an endergonic reaction in cells?

Accepted Answer

The phosphorylation of glucose to glucose-6-phosphate, driven by ATP hydrolysis.

Question 6

How do enzymes increase the rate of metabolic reactions?

Accepted Answer

By lowering the activation energy ($$ E_a ) $$required for the reaction.

Question 7

A metabolic pathway is regulated by feedback inhibition. Which of the following best describes this process?

Accepted Answer

The final product of the pathway inhibits the first enzyme in the pathway.

Question 8

Which of the following statements about exergonic and endergonic reactions is correct?

Accepted Answer

Exergonic reactions have $$ \Delta G \u003c 0 $$ and are spontaneous.

Question 9

Which scenario best illustrates the Second Law of Thermodynamics in a biological context?

Accepted Answer

A cell uses energy from ATP to create order locally, but releases heat, increasing the disorder of the surroundings.

Question 10

Which of the following is NOT a way that enzyme activity can be regulated in cells?

Accepted Answer

Changing the DNA sequence of the enzyme.

Question 11

A scientist measures the $$ \Delta G  of a $$reaction and finds it to be $$ +5  kJ/$$mol. What does this indicate about the reaction?

Accepted Answer

The reaction is endergonic and requires an input of energy to proceed.

Question 12

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 that fits only specific substrates.

Question 13

If a cell's ATP supply is depleted, which of the following processes would be most directly affected?

Accepted Answer

Active transport of ions against their concentration gradient.

Question 14

Which of the following is a correct statement about the relationship between free energy and stability?

Accepted Answer

Systems with lower free energy are more stable.

Question 15

A mutation causes an enzyme's active site to change shape. What is the most likely consequence?

Accepted Answer

The enzyme may no longer bind its substrate, reducing or eliminating its activity.

Question 16

Which of the following best describes the role of entropy ($$ S ) in $$biological systems according to the Second Law of Thermodynamics?

Accepted Answer

Biological systems increase the entropy of the universe even as they maintain local order.

Question 17

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

Accepted Answer

A molecule binds to a site other than the active site, changing the enzyme's shape and activity.

Question 18

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

Accepted Answer

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

Question 19

A patient is given a drug 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 because the inhibitor binds to a site other than the active site, altering enzyme function.

Question 20

Which of the following best describes the relationship between metabolic pathways and enzyme regulation?

Accepted Answer

Enzyme regulation allows cells to control the flow of metabolites and respond to changing conditions.

Energy, Thermodynamics, and Enzymes in Biological Systems

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