Question 1

Which of the following 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 bear eats a fish and then runs, generating heat. Which law of thermodynamics does this scenario illustrate, and why?

Accepted Answer

Second law, because energy transformation increases entropy as heat is released.

Question 3

Which of the following equations correctly represents the change in free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

$$\Delta G = G_{final} - G_{initial}$$

Question 4

Which of the following is true about exergonic reactions in metabolism?

Accepted Answer

They proceed with a net release of free energy and have a negative $$\Delta G.$$

Question 5

Photosynthesis is an example of which type of metabolic reaction, and what is the sign of $$\Delta G$$ for this process?

Accepted Answer

Anabolic; $$\Delta G is $$positive

Question 6

Why do living cells never reach equilibrium in their metabolic pathways?

Accepted Answer

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

Question 7

Which of the following statements about ATP hydrolysis is correct?

Accepted Answer

ATP hydrolysis releases energy due to the repulsive force of the phosphate groups.

Question 8

How does ATP typically power cellular work?

Accepted Answer

By coupling exergonic ATP hydrolysis to endergonic reactions via phosphorylation.

Question 9

Which of the following best explains why enzymes are necessary for metabolic reactions?

Accepted Answer

Enzymes lower the activation energy ($$E_a$$), allowing reactions to occur at moderate temperatures.

Question 10

A patient is given a drug that acts as a competitive inhibitor for a key metabolic enzyme. What is the most likely effect of this drug?

Accepted Answer

It binds to the active site, preventing substrate binding.

Question 11

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

Accepted Answer

The end product of a pathway inhibits an enzyme that acts early in the pathway.

Question 12

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

Accepted Answer

Cofactors are nonprotein molecules that assist enzymes in catalysis.

Question 13

A mutation changes the amino acid sequence of an enzyme, resulting in a new substrate specificity. What is the evolutionary significance of this change?

Accepted Answer

If the new function is beneficial, the altered enzyme may persist in the population.

Question 14

Which of the following is NOT a way that enzymes lower activation energy ($$E_a$$)?

Accepted Answer

Increasing the temperature of the reaction.

Question 15

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 in organisms, but the total entropy of the universe increases.

Question 16

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

Accepted Answer

As free energy decreases, the stability of a system increases.

Question 17

Which of the following is an example of energy coupling in a cell?

Accepted Answer

The use of ATP hydrolysis to drive the synthesis of glutamine from glutamic acid and ammonia.

Question 18

Which of the following best describes the effect of temperature on enzyme activity?

Accepted Answer

Enzyme activity increases with temperature up to an optimal point, then decreases as the enzyme denatures.

Question 19

Which of the following statements about allosteric regulation is correct?

Accepted Answer

Allosteric regulation can either inhibit or stimulate enzyme activity by binding to a site other than the active site.

Question 20

A scientist observes that increasing substrate concentration increases the rate of an enzyme-catalyzed reaction, but only up to a certain point. What is the most likely explanation for this observation?

Accepted Answer

The enzyme is saturated; all active sites are occupied, so adding more substrate does not increase the rate.

Chapter 6: An Introduction to Metabolism – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard