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 cell synthesizes a protein from amino acids. Which of the following statements about this process is correct?

Accepted Answer

It is a nonspontaneous, endergonic reaction because it requires an input of energy.

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 best explains why living organisms do not violate the second law of thermodynamics?

Accepted Answer

Organisms decrease their own entropy, but increase the entropy of their surroundings.

Question 5

A reaction has a $$\Delta G of$$ $$-15 kJ/$$mol. What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and will occur spontaneously.

Question 6

Which of the following is an example of energy coupling in cells?

Accepted Answer

The hydrolysis of ATP drives the synthesis of glutamine from glutamic acid and ammonia.

Question 7

Which of the following statements about enzymes is correct?

Accepted Answer

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

Question 8

A patient with scurvy is suffering from a deficiency in which vitamin, and what is the primary biochemical consequence?

Accepted Answer

Vitamin C; defective collagen synthesis due to lack of hydroxylation of proline residues

Question 9

Which of the following best describes competitive inhibition of an enzyme?

Accepted Answer

The inhibitor binds to the active site, preventing substrate binding.

Question 10

Which of the following scenarios illustrates feedback inhibition in a metabolic pathway?

Accepted Answer

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

Question 11

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

Accepted Answer

ATP contains high-energy phosphate bonds that, when hydrolyzed, release energy that can be used to drive endergonic reactions.

Question 12

A scientist adds an enzyme to a reaction mixture that is already at equilibrium. What will happen?

Accepted Answer

There will be no net change; the enzyme will not affect the equilibrium position.

Question 13

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

Accepted Answer

A system with lower free energy is more stable than one with higher free energy.

Question 14

Which of the following best describes allosteric regulation of an enzyme?

Accepted Answer

A regulatory molecule binds to a site other than the active site, causing a conformational change that affects enzyme activity.

Question 15

Which of the following is an example of an exergonic reaction in cellular metabolism?

Accepted Answer

The hydrolysis of ATP to ADP and inorganic phosphate ($$ATP \rightarrow ADP + P_i)$$

Question 16

Which of the following statements about metabolic pathways is correct?

Accepted Answer

Each step in a metabolic pathway is catalyzed by a specific enzyme.

Question 17

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The shape and chemical environment of the enzyme's active site are complementary to the substrate.

Question 18

Which of the following is a real-world example of enzyme inhibition with medical relevance?

Accepted Answer

Penicillin inhibits bacterial cell wall synthesis by blocking a key enzyme.

Question 19

Which of the following statements about the hydrolysis of ATP is correct?

Accepted Answer

It is an exergonic reaction that releases energy.

Question 20

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

Accepted Answer

Each enzyme has an optimal temperature at which its activity is maximal; activity decreases above or below this temperature.

Introduction to Metabolism: Principles and Pathways

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