Question 1

Which of the following statements best describes energetic coupling in biological systems?

Accepted Answer

Energetic coupling is the process by which an exergonic reaction provides the energy required to drive an endergonic reaction, as long as the total $$\Delta G of $$the coupled reactions is less than zero.

Question 2

Refer to the ATP cycle diagram (Image 1). What is the $$\Delta G$$ for the hydrolysis of ATP to ADP and inorganic phosphate?

Accepted Answer

$$\Delta G = -7.3$$ kcal/mol

Question 3

Which of the following is true regarding redox reactions, as illustrated in Image 2?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 4

In the context of moving ions down their electrochemical gradient (Image 3), which statement is correct?

Accepted Answer

Moving ions down their electrochemical gradient is an exergonic process with $$\Delta G \u003c 0.$$

Question 5

Which level of protein structure is directly responsible for the specificity of enzyme active sites, as shown in Image 4?

Accepted Answer

Tertiary structure

Question 6

Based on Image 5, what is the role of the enzyme glucokinase in the reaction with glucose and ATP?

Accepted Answer

It brings the substrates together in the correct orientation and stabilizes the transition state.

Question 7

Refer to the free energy diagram (Image 6). What does the height of the peak labeled $$E_a$$ represent?

Accepted Answer

The activation energy required for the reaction to proceed.

Question 8

How does the presence of an enzyme affect the reaction profile shown in Image 7?

Accepted Answer

It lowers the activation energy ($$E_a) $$but does not change the overall $$\Delta G of $$the reaction.

Question 9

Which of the following best describes the induced fit model of enzyme action, as shown in Image 8?

Accepted Answer

The enzyme changes shape to better fit the substrates and stabilize the transition state.

Question 10

Based on the enzyme activity graphs (Image 9), which statement is correct regarding enzyme adaptation?

Accepted Answer

Enzymes from bacteria in hot, acidic environments have higher optimal temperatures and lower optimal pH than those from cool, neutral environments.

Question 11

Which of the following scenarios best illustrates competitive inhibition, as shown in Image 10a?

Accepted Answer

A molecule binds to the enzyme's active site, preventing the substrate from binding.

Question 12

Which of the following is an example of allosteric regulation (activation), as shown in Image 10b?

Accepted Answer

A regulatory molecule binds to a site other than the active site, causing the enzyme to become active.

Question 13

A scientist observes that an enzyme-catalyzed reaction proceeds much faster at pH 7 than at pH 3. What is the most likely explanation?

Accepted Answer

The enzyme's active site is optimized for pH 7, and extreme pH disrupts its structure.

Question 14

Which of the following statements about enzymes is FALSE?

Accepted Answer

Enzymes change the overall $$\Delta G of a $$reaction.

Question 15

A cell needs to drive an endergonic reaction with $$\Delta G = +5$$ kcal/mol. Which of the following exergonic reactions could be coupled to make the overall process spontaneous?

Accepted Answer

A reaction with $$\Delta G = -7$$ kcal/mol

Question 16

Which of the following best explains why enzymes do not alter the equilibrium position of a chemical reaction?

Accepted Answer

Enzymes only lower the activation energy, not the $$\Delta G$$, so the ratio of products to reactants at equilibrium remains unchanged.

Question 17

A mutation causes an enzyme's active site to become less specific. What is the most likely consequence?

Accepted Answer

The enzyme will catalyze a wider range of reactions, possibly leading to harmful side reactions.

Question 18

Which of the following is a real-life example of energetic coupling in human cells?

Accepted Answer

Using ATP hydrolysis to power the active transport of sodium ions against their concentration gradient.

Energetic Coupling and Enzyme Function in Cellular Metabolism

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