Question 1

Which of the following best describes the difference between catabolic and anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down complex molecules to release energy, while anabolic pathways build complex molecules and require energy input.

Question 2

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

Accepted Answer

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

Question 3

A chemical reaction has a negative change in free energy ($$\Delta G \u003c 0). $$Which of the following is true about this reaction?

Accepted Answer

It is an exergonic reaction and releases energy.

Question 4

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

Accepted Answer

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

Question 5

A reaction in a cell has a $$\Delta G of $$zero. What does this indicate about the reaction?

Accepted Answer

The reaction is at equilibrium and can do no work.

Question 6

Which of the following scenarios best illustrates energy coupling in metabolism?

Accepted Answer

The hydrolysis of ATP is used to drive the synthesis of glucose from carbon dioxide.

Question 7

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy, increasing the rate of a reaction without being consumed.

Question 8

A competitive inhibitor affects an enzyme by:

Accepted Answer

Binding reversibly to the active site, blocking substrate binding.

Question 9

Which of the following would most likely decrease the rate of an enzyme-catalyzed reaction?

Accepted Answer

Adding a noncompetitive inhibitor that binds to a site other than the active site.

Question 10

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

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

Question 11

A scientist observes that a certain enzyme works optimally at pH 7.4 and 37°C. What is most likely to happen if the enzyme is placed in a solution at pH 3.0 and 60°C?

Accepted Answer

The enzyme will denature, losing its structure and function.

Question 12

Which of the following is true regarding the second law of thermodynamics as it applies to living organisms?

Accepted Answer

Living organisms increase the entropy of their surroundings while maintaining order internally.

Question 13

Which of the following best explains why exergonic reactions can be used to drive endergonic reactions in cells?

Accepted Answer

The energy released by exergonic reactions can be coupled to endergonic reactions, making the overall process energetically favorable.

Question 14

A cell is exposed to a molecule that binds irreversibly to the active site of an essential enzyme. What is the most likely outcome?

Accepted Answer

The enzyme will be permanently inactivated, and the reaction it catalyzes will stop.

Question 15

Which of the following is a correct statement about the relationship between free energy ($$G$$), enthalpy ($$H$$), entropy ($$S$$), and temperature ($$T) in a $$chemical reaction?

Accepted Answer

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

Question 16

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 snugly upon binding.

Question 17

Which of the following is NOT a way that a cell can regulate enzyme activity?

Accepted Answer

Increasing the activation energy required for the reaction.

Question 18

A metabolic pathway is regulated by negative feedback. Which of the following would you expect to observe?

Accepted Answer

The end product of the pathway inhibits the activity of an enzyme early in the pathway.

Question 19

Which of the following best explains why chemical reactions at equilibrium do not perform work in cells?

Accepted Answer

At equilibrium, $$\Delta G = 0$$, so no free energy is available to do work.

LEC 5 Metabolism and Enzyme Function in Cells

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