Q: A reaction has $$\Delta H = -686$$ kcal/mol, $$\Delta S = +0.18$$ kcal/mol\cdot K, and $$T = 298 K. $$What is $$\Delta G$$ for this reaction, and is it spontaneous?

$$ \Delta G = -739.64 \text{ kcal/mol}; $$ The reaction is spontaneous.

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

Which of the following is an example of potential energy in a biological system?

Accepted Answer

The chemical bonds in a molecule of glucose.

Question 3

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

Accepted Answer

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

Question 4

Which equation correctly represents the Gibbs free energy change for a reaction?

Accepted Answer

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

Question 5

A reaction has $$\Delta H = -686$$ kcal/mol, $$\Delta S = +0.18$$ kcal/mol\cdot K, and $$T = 298 K. $$What is $$\Delta G$$ for this reaction, and is it spontaneous?

Accepted Answer

$$ \Delta G = -739.64 	ext{ kcal/mol}; $$ The reaction is spontaneous.

Question 6

Which of the following best explains why ATP hydrolysis releases so much energy?

Accepted Answer

The repulsive force of the three negatively charged phosphate groups is relieved during hydrolysis.

Question 7

Which process is an example of energy coupling in cells?

Accepted Answer

The sodium-potassium pump using ATP hydrolysis to transport ions against their gradients.

Question 8

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy barrier, speeding up reactions.

Question 9

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

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 10

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of a pathway binds to an enzyme early in the pathway, inhibiting its activity.

Question 11

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

Accepted Answer

Every energy transfer or transformation increases the entropy of the universe.

Question 12

Which of the following is true about exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions have a negative $$\Delta G$$ and are spontaneous.

Question 13

Which of the following is NOT a form of work powered by ATP in cells?

Accepted Answer

Passive diffusion of gases across a membrane.

Question 14

Which of the following statements about metabolic pathways is correct?

Accepted Answer

A metabolic pathway begins with a specific molecule and ends with a product, with each step catalyzed by a specific enzyme.

Question 15

Which of the following is an example of an anabolic pathway?

Accepted Answer

The synthesis of proteins from amino acids.

Question 16

Which of the following best explains why the evolution of complex organisms does not violate the second law of thermodynamics?

Accepted Answer

Entropy may decrease locally within an organism, but the total entropy of the universe increases.

Question 17

Which of the following is true about the effect of temperature on enzyme activity?

Accepted Answer

Each enzyme has an optimal temperature, above which the enzyme denatures and activity decreases.

Question 18

Which of the following is a correct statement about cofactors and coenzymes?

Accepted Answer

Coenzymes are organic cofactors, often derived from vitamins.

Question 19

Which of the following is an example of allosteric regulation?

Accepted Answer

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

Question 20

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

Accepted Answer

The enzyme changes shape slightly to fit the substrate more closely upon binding.

Energy, Metabolism, and Thermodynamics in Biological Systems

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