Question 1

Which statement best describes the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 2

A scientist measures the free-energy change ($$\Delta G) of a $$reaction and finds it to be negative. What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and will occur spontaneously.

Question 3

Which of the following best distinguishes between exergonic and endergonic reactions in terms of free energy change ($$\Delta G$$)?

Accepted Answer

Exergonic reactions have $$\Delta G  0.$$

Question 4

How does ATP power cellular work by coupling exergonic reactions to endergonic reactions?

Accepted Answer

ATP hydrolysis releases energy that is directly transferred to endergonic reactions.

Question 5

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

Accepted Answer

Thermal work, such as maintaining body temperature

Question 6

What is the relationship between ATP and ADP in cellular energy transfer?

Accepted Answer

ATP is formed by the addition of a phosphate group to ADP, storing energy.

Question 7

Which factor does NOT affect the rate of enzyme-catalyzed reactions?

Accepted Answer

The color of the enzyme

Question 8

How does the structure of an enzyme determine its specificity?

Accepted Answer

The enzyme's active site has a unique shape that fits only specific substrates.

Question 9

A patient has a fever of 40°C. How might this affect the activity of their enzymes?

Accepted Answer

Enzyme activity may decrease because high temperatures can denature enzymes.

Question 10

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

Accepted Answer

An inhibitor binds to the active site, blocking substrate binding.

Question 11

A metabolic pathway is regulated by feedback inhibition. Which of the following best explains this process?

Accepted Answer

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

Question 12

Which of the following is an example of allosteric regulation in enzymes?

Accepted Answer

A molecule binds to a site other than the active site, changing the enzyme's activity.

Question 13

If a cell's ATP levels are low, which of the following is most likely to occur?

Accepted Answer

The cell will increase catabolic reactions to generate more ATP.

Question 14

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

Accepted Answer

Enzymes lower the activation energy barrier, allowing reactions to occur at cellular temperatures.

Question 15

A researcher adds a noncompetitive inhibitor to an enzyme-catalyzed reaction. What is the most likely effect?

Accepted Answer

The inhibitor binds to a site other than the active site, reducing enzyme activity.

Question 16

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

Accepted Answer

The final product of a pathway binds to the first enzyme, decreasing its activity.

Question 17

Which equation correctly represents the hydrolysis of ATP?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 18

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

Accepted Answer

The enzyme will be permanently inactivated, and the metabolic pathway will be disrupted.

Question 19

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

Accepted Answer

Each enzyme has an optimal pH at which it functions best; deviations can reduce activity.

Question 20

In the context of cellular metabolism, what is the primary benefit of feedback inhibition?

Accepted Answer

It prevents the overaccumulation of end products and conserves cellular resources.

Cellular Energy and Metabolism: Thermodynamics, ATP, and Enzyme Regulation

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