Question 1

Which of the following best describes the function of the gastric proton pump (H$$^+$$, K$$^+-$$ATPase) in the stomach?

Accepted Answer

It actively transports hydrogen ions into the stomach lumen in exchange for potassium ions, using ATP.

Question 2

A patient is prescribed a proton pump inhibitor (PPI) for chronic heartburn. What is the primary effect of this medication at the molecular level?

Accepted Answer

It inhibits the enzyme responsible for pumping protons into the stomach, reducing gastric acidity.

Question 3

Which law of thermodynamics explains why energy cannot be created or destroyed in biological systems?

Accepted Answer

The 1st Law of Thermodynamics

Question 4

According to the 2nd Law of Thermodynamics, what happens to the entropy of the universe during any energy transformation?

Accepted Answer

It increases.

Question 5

Which of the following reactions is most likely to occur spontaneously?

Accepted Answer

A reaction that decreases the potential energy of the products.

Question 6

What is the formula for calculating the change in Gibbs free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

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

Question 7

ATP hydrolysis is often coupled to cellular processes that require energy. If the $$\Delta G$$ for ATP hydrolysis is $$-7.3$$ kcal/mol and the $$\Delta G$$ for ion active transport is $$2.3$$ kcal/mol, what is the net $$\Delta G$$ for the coupled reaction?

Accepted Answer

$$-5.0$$ kcal/mol

Question 8

Which statement best explains why gasoline does not spontaneously explode in your car’s gas tank?

Accepted Answer

The activation energy barrier prevents the reaction from occurring spontaneously.

Question 9

Enzymes speed up chemical reactions by:

Accepted Answer

Decreasing the activation energy required for the reaction.

Question 10

Which of the following is an example of competitive inhibition?

Accepted Answer

A molecule similar to the substrate binds to the active site, preventing substrate binding.

Question 11

What happens to a protein when it is denatured?

Accepted Answer

Its 3D shape is altered due to disruption of hydrogen bonds.

Question 12

Which level of protein structure is defined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 13

A reaction that builds polymers from monomers is best described as:

Accepted Answer

Anabolic and endergonic

Question 14

Which of the following best describes entropy?

Accepted Answer

A measure of disorder or randomness in a system

Question 15

Which scenario best illustrates the concept of increasing entropy?

Accepted Answer

A clean room becoming messy over time without cleaning

Question 16

Which of the following statements about energy in biological systems is correct?

Accepted Answer

Energy can be transformed from one form to another but cannot be destroyed.

Question 17

Which of the following is true about ATP hydrolysis in cells?

Accepted Answer

It releases energy that can be used to drive other cellular processes.

Question 18

Which of the following best explains why cells must constantly hydrolyze ATP?

Accepted Answer

Cells require a continuous supply of energy for endergonic processes.

Question 19

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

Accepted Answer

Using the energy from ATP hydrolysis to power active transport of ions across a membrane.

Question 20

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

Accepted Answer

A molecule binds to a site other than the active site, changing the enzyme’s shape.

Energy, Thermodynamics, and Enzymes in Biological Systems

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