Question 1

Which of the following best describes the difference between catabolic and anabolic pathways in 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 runner eats a meal rich in carbohydrates before a race. Which form of energy is stored in the carbohydrates, and what type of energy transformation occurs as the runner sprints?

Accepted Answer

Chemical energy is stored in carbohydrates, and it is transformed into kinetic and thermal energy as the runner sprints.

Question 3

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

Accepted Answer

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

Question 4

Which of the following scenarios best illustrates the second law of thermodynamics?

Accepted Answer

A bear eating a fish and releasing heat and $$\mathrm{CO_2$} as $$byproducts.

Question 5

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 6

Which of the following is true for an exergonic reaction?

Accepted Answer

It releases energy, is spontaneous, and has a negative $$\Delta G.$$

Question 7

Why do cells never reach equilibrium in their metabolic pathways?

Accepted Answer

Because equilibrium would mean no net work can be done, and cells are open systems that constantly exchange materials and energy.

Question 8

ATP hydrolysis is often coupled to endergonic reactions in cells. Which statement best explains why?

Accepted Answer

ATP hydrolysis releases energy, making it possible to drive nonspontaneous (endergonic) reactions by coupling.

Question 9

Which of the following best describes how enzymes speed up chemical reactions?

Accepted Answer

Enzymes lower the activation energy ($$E_a) $$required for the reaction to proceed.

Question 10

A patient is given a drug that acts as a competitive inhibitor for a key metabolic enzyme. Which of the following best describes how this drug works?

Accepted Answer

It binds to the active site, blocking the substrate from binding.

Question 11

Which of the following would most likely increase the rate of an enzyme-catalyzed reaction that is currently operating below its optimal temperature?

Accepted Answer

Increasing the temperature to the enzyme's optimal range.

Question 12

In a metabolic pathway, the end product inhibits an enzyme that acts early in the pathway. What is this regulatory mechanism called?

Accepted Answer

Feedback inhibition

Question 13

Which of the following is an example of potential energy in a biological system?

Accepted Answer

The chemical bonds in a molecule of glucose.

Question 14

A scientist measures the $$\Delta G of a $$reaction and finds it to be positive. What can be concluded about this reaction?

Accepted Answer

The reaction is endergonic and requires an input of energy.

Question 15

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

Accepted Answer

The active site of an enzyme has a unique shape that fits only specific substrates, often through an induced fit mechanism.

Question 16

A metabolic pathway in a cell is shut down when the concentration of its end product increases. This is an example of:

Accepted Answer

Feedback inhibition

Question 17

Which of the following statements about open and closed systems is correct in the context of biological organisms?

Accepted Answer

Organisms are open systems that exchange both energy and matter with their surroundings.

Question 18

Which of the following best describes the role of ATP in cellular metabolism?

Accepted Answer

ATP provides energy for cellular work by transferring a phosphate group to other molecules (phosphorylation).

Question 19

A noncompetitive inhibitor decreases the rate of an enzyme-catalyzed reaction by:

Accepted Answer

Binding to a site other than the active site, causing a conformational change in the enzyme.

Question 20

Which of the following is a real-world example of the second law of thermodynamics in biological systems?

Accepted Answer

A cell using glucose to generate ATP and releasing heat as a byproduct.

ch 8

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