Question 1

Which of the following statements best describes the first law of thermodynamics as it applies to biological systems?

Accepted Answer

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

Question 2

A cell assembles a protein from amino acids. This process is an example of which type of metabolic pathway?

Accepted Answer

Anabolic pathway

Question 3

Which of the following best explains why the hydrolysis of ATP is used to drive endergonic reactions in cells?

Accepted Answer

ATP hydrolysis releases free energy that can be coupled to drive nonspontaneous reactions.

Question 4

Given the equation for free energy change: $$\Delta G = \Delta H - T\Delta S$$, which scenario would most likely result in a spontaneous reaction?

Accepted Answer

$$\Delta H is $$negative and $$\Delta S is $$positive

Question 5

Which of the following is true about enzymes and their effect on chemical reactions?

Accepted Answer

Enzymes lower the activation energy barrier, allowing reactions to occur more rapidly.

Question 6

A competitive inhibitor decreases the rate of an enzyme-catalyzed reaction by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 7

Which of the following best describes the role of cofactors in enzyme activity?

Accepted Answer

Cofactors are nonprotein helpers that are required for some enzymes to function.

Question 8

Which of the following is an example of energy transformation in a biological system that illustrates both the first and second laws of thermodynamics?

Accepted Answer

A bear eating a fish, converting chemical energy to kinetic energy, and releasing heat.

Question 9

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

Accepted Answer

Exergonic reactions have a negative $$\Delta G$$ and occur spontaneously.

Question 10

A scientist observes that an enzyme-catalyzed reaction proceeds much faster at pH 7 than at pH 2 or pH 10. What is the most likely explanation?

Accepted Answer

The enzyme has an optimal pH near 7, and extreme pH values reduce its activity.

Question 11

Which of the following best explains why cells do not spontaneously break down all their macromolecules, even though these reactions are exergonic?

Accepted Answer

The activation energy barrier prevents spontaneous breakdown.

Question 12

Which of the following is a real-life example of energy coupling in cells?

Accepted Answer

The hydrolysis of ATP is used to power the active transport of ions across a membrane.

Question 13

Which of the following is true about the induced fit model of enzyme function?

Accepted Answer

The enzyme changes shape slightly to fit more snugly around the substrate.

Question 14

A reaction has $$\Delta G = +5$$ kcal/mol. Which of the following statements is true?

Accepted Answer

The reaction is endergonic and requires an input of energy.

Question 15

Which of the following best describes the ATP cycle in cells?

Accepted Answer

ATP is synthesized from ADP and phosphate using energy from catabolic reactions, and hydrolyzed to power cellular work.

Question 16

Which of the following would most likely increase the rate of an enzyme-catalyzed reaction?

Accepted Answer

Adding more substrate when a competitive inhibitor is present.

Question 17

Which of the following is an example of a catabolic pathway?

Accepted Answer

The breakdown of glucose during cellular respiration.

Question 18

Which of the following statements about noncompetitive enzyme inhibitors is correct?

Accepted Answer

They bind to a different site on the enzyme, changing its shape and reducing activity.

Question 19

A reaction in a cell has $$\Delta H = -10$$ kcal/mol, $$\Delta S = +0.02$$ kcal/(mol·K), and occurs at $$T = 300 K. $$What is $$\Delta G$$ for this reaction, and is it spontaneous?

Accepted Answer

$$\Delta G = -10.6$$ kcal/mol; the reaction is spontaneous.

Chapter 8: An Introduction to Metabolism – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards