Question 1

Which of the following best distinguishes catabolic pathways from anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down complex molecules into simpler ones, releasing energy, while anabolic pathways build complex molecules from simpler ones, requiring energy input.

Question 2

A ball held at the top of a hill possesses which form of energy, and what is a biological example of this energy type?

Accepted Answer

Potential energy; chemical bonds in ATP

Question 3

Which statement correctly describes the first law of thermodynamics as it applies to biological systems?

Accepted Answer

Energy is transferred from one organism to another, but the total energy in the universe remains constant.

Question 4

During a chemical reaction, the change in free energy ($$\Delta G) is $$calculated using which equation?

Accepted Answer

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

Question 5

A reaction with $$\Delta G \u003c 0 is $$best described as:

Accepted Answer

Spontaneous and exergonic

Question 6

Why do biological organisms not violate the second law of thermodynamics, even though they maintain order within their cells?

Accepted Answer

They increase the entropy of their surroundings by releasing heat and waste, resulting in a net increase in universal entropy.

Question 7

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

Accepted Answer

Photosynthetic work

Question 8

ATP hydrolysis releases a significant amount of free energy because:

Accepted Answer

The repulsion between negatively charged phosphate groups is relieved when a phosphate is removed.

Question 9

In the process of ATP-driven glutamine synthesis, what is a phosphorylated intermediate?

Accepted Answer

A molecule that has gained a phosphate group from ATP, making it more reactive.

Question 10

Which of the following statements about enzymes is TRUE?

Accepted Answer

Enzymes lower the activation energy but do not change the $$\Delta G of $$the reaction.

Question 11

A competitive inhibitor differs from a noncompetitive inhibitor in that a competitive inhibitor:

Accepted Answer

Binds to the active site and prevents substrate binding.

Question 12

Which environmental factor would most likely decrease the rate of an enzyme-catalyzed reaction in the human body?

Accepted Answer

Decreasing the pH from 7.4 to 2

Question 13

Feedback inhibition in a metabolic pathway is best described as:

Accepted Answer

The end product of the pathway acts as an allosteric inhibitor of an enzyme earlier in the pathway.

Question 14

Which of the following best explains why metabolic reactions in living organisms do NOT reach chemical equilibrium?

Accepted Answer

Metabolic pathways are open systems with a constant flow of materials, preventing equilibrium.

Question 15

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 16

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 17

A mutation in the gene encoding an enzyme changes the amino acid sequence of the enzyme's active site. What is the most likely consequence?

Accepted Answer

The enzyme may lose its substrate specificity and catalytic activity.

Question 18

Which of the following scenarios illustrates the coupling of exergonic and endergonic reactions in a cell?

Accepted Answer

ATP hydrolysis (exergonic) provides energy for glucose synthesis (endergonic).

Question 19

Which of the following best describes the difference between open and closed systems in thermodynamics as applied to cells?

Accepted Answer

Open systems exchange energy and matter with their surroundings, while closed systems do not.

Chapter 6: An Introduction to Metabolism – Study Notes

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