Q: A scientist measures the enthalpy change ($$\Delta H) $$and entropy change ($$\Delta S) of a $$reaction at 298 K. If $$\Delta H = +10 kJ/$$mol and $$\Delta S = +50 J/($$mol·K), what is $$\Delta G$$ for the reaction? (Note: 1 kJ = 1000 J)

$$\Delta G = +10,000 - (298 \times 50) = -4,900 J/$$mol

Question 1

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

Accepted Answer

Energy is transformed from one form to another, but the total amount remains constant.

Question 2

A runner eats a meal rich in carbohydrates before a race. Which process best illustrates the transformation of energy in this scenario?

Accepted Answer

Chemical energy in glucose is converted to kinetic energy as the runner moves.

Question 3

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 4

Which of the following statements about entropy ($$S) is $$correct in the context of the second law of thermodynamics?

Accepted Answer

Entropy tends to increase in spontaneous processes, leading to greater disorder.

Question 5

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

Accepted Answer

Synthesis of glucose during photosynthesis

Question 6

A scientist measures the enthalpy change ($$\Delta H) $$and entropy change ($$\Delta S) of a $$reaction at 298 K. If $$\Delta H = +10 kJ/$$mol and $$\Delta S = +50 J/($$mol·K), what is $$\Delta G$$ for the reaction? (Note: 1 kJ = 1000 J)

Accepted Answer

$$\Delta G = +10,000 - (298 	imes 50) = -4,900 J/$$mol

Question 7

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

Accepted Answer

ATP can directly transfer a phosphate group to other molecules, releasing energy for cellular work.

Question 8

Which of the following best describes the role of enzymes in chemical reactions?

Accepted Answer

Enzymes lower the activation energy, increasing the rate of the reaction.

Question 9

A mutation changes the shape of an enzyme's active site. What is the most likely consequence?

Accepted Answer

The enzyme will lose its specificity and may not function properly.

Question 10

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

Accepted Answer

A product of the pathway binds to an allosteric site on the first enzyme, decreasing its activity.

Question 11

Which of the following best describes the difference between competitive and noncompetitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind to the active site, while noncompetitive inhibitors bind to a different site on the enzyme.

Question 12

During a marathon, a runner's muscle cells switch from aerobic to anaerobic metabolism. Which statement best explains this metabolic shift?

Accepted Answer

Oxygen becomes limited, so cells use anaerobic pathways to continue producing ATP.

Question 13

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

Accepted Answer

The energy released by exergonic reactions is used to drive endergonic reactions.

Question 14

Which of the following best describes the specificity of an enzyme for its substrate?

Accepted Answer

Enzyme specificity is determined by the shape and chemical properties of the active site.

Question 15

A patient is diagnosed with a genetic disorder that results in a nonfunctional enzyme in a metabolic pathway. Which of the following is the most likely consequence?

Accepted Answer

The substrate for the defective enzyme will accumulate, and the final product will be deficient.

Question 16

Which of the following best explains why some energy is lost as heat during metabolic reactions?

Accepted Answer

Heat is a form of energy that cannot be used to do work in biological systems.

Question 17

Which of the following is NOT a function of ATP in the cell?

Accepted Answer

Serving as a building block for DNA synthesis

Question 18

Which of the following best describes 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 19

Which of the following scenarios best illustrates the concept of free energy ($$\Delta G) in a $$biological reaction?

Accepted Answer

A reaction with $$\Delta G \u003c 0 is $$spontaneous and can perform work in the cell.

Chapter 8: An Introduction to Metabolism – Study Notes

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