Question 1

Which of the following statements best describes the role of free energy change ($$\Delta G) in $$determining whether a biochemical reaction will proceed spontaneously?

Accepted Answer

A reaction will proceed spontaneously if $$\Delta G is $$negative, indicating a net loss of energy.

Question 2

Given the equation $$\Delta G = \Delta G^0$ + RT \ln \frac{[B]}{[A]}$$, what will happen to $$\Delta G if $$the concentration of product $$[B] is $$much less than the concentration of reactant $$[A]$$?

Accepted Answer

$$\Delta G$$ will become more negative, favoring the forward reaction.

Question 3

Which of the following best explains why ATP hydrolysis is commonly used to drive endergonic reactions in cells?

Accepted Answer

ATP hydrolysis has a large negative $$\Delta G$$, making it energetically favorable and able to drive unfavorable reactions.

Question 4

A metabolic pathway consists of the following reactions:

1. Glucose + ATP $$\rightarrow$$ Glucose 6-phosphate + ADP ($$\Delta G^0$ = -4,000$$ cal/mol)
2. Glucose 6-phosphate $$\rightarrow$$ Fructose 6-phosphate ($$\Delta G^0$ = +400$$ cal/mol)

What is the overall standard free energy change ($$\Delta G^0$) for the pathway from glucose to fructose 6-phosphate?

Accepted Answer

$$-3,600$$ cal/mol

Question 5

Which of the following is TRUE regarding the relationship between $$\Delta G^0$ and the equilibrium constant K$$_{eq}$$?

Accepted Answer

$$\Delta G^0$ = -RT \ln K_{eq}$$

Question 6

In the electron transport chain (ETC), which complex is responsible for transferring electrons from NADH to coenzyme Q (CoQ)?

Accepted Answer

Complex I

Question 7

Which statement best describes the chemiosmotic hypothesis for ATP synthesis in mitochondria?

Accepted Answer

ATP synthesis is driven by the energy released from the movement of protons (H$$^+) $$down their gradient through ATP synthase.

Question 8

If a cell is exposed to an uncoupling agent such as 2,4-dinitrophenol, what is the most likely consequence for oxidative phosphorylation?

Accepted Answer

Electron transport continues, but ATP synthesis is greatly reduced and energy is released as heat.

Question 9

Which of the following best describes the function of cytochrome c oxidase (Complex IV) in the electron transport chain?

Accepted Answer

It is the only complex that can bind oxygen and catalyze its reduction to water.

Question 10

A mutation in mitochondrial DNA affects the function of ATP synthase. Which tissue is most likely to be severely affected?

Accepted Answer

Skeletal muscle

Question 11

Which of the following equations correctly relates the standard free energy change ($$\Delta G^0$) to the change in standard reduction potential ($$\Delta $$E^0) $$for a redox reaction?

Accepted Answer

$$\Delta G^0$ = -nF \Delta E^0$

Question 12

Which of the following is a consequence of inhibiting electron flow at Complex III of the ETC?

Accepted Answer

Electron carriers before the block become reduced, while those after the block become oxidized.

Question 13

Which of the following best explains why brown adipose tissue is important for thermogenesis in mammals?

Accepted Answer

It contains uncoupling proteins that allow protons to re-enter the mitochondrial matrix without generating ATP, releasing energy as heat.

Question 14

Which of the following statements about the mitochondrial inner membrane is CORRECT?

Accepted Answer

It is impermeable to most small ions and metabolites, requiring specialized transport systems.

Question 15

During apoptosis, which event is directly responsible for the activation of caspases?

Accepted Answer

Release of cytochrome c from the mitochondrial intermembrane space into the cytosol.

Question 16

Which of the following is TRUE regarding the direction of a reaction under standard conditions?

Accepted Answer

The direction can be predicted using $$\Delta G^0$ because $$\Delta $$G^0$$ = \Delta G$$ under standard conditions.

Question 17

Which of the following best describes the role of NADH and FADH$$_2 in $$cellular respiration?

Accepted Answer

They act as electron donors to the electron transport chain, enabling ATP synthesis.

Question 18

If the equilibrium constant $$K_{eq}$$ for a reaction is less than 1, what can be inferred about $$\Delta G^0$?

Accepted Answer

$$\Delta G^0$ is positive.

Question 19

Which of the following transporters is responsible for exchanging ATP and ADP across the inner mitochondrial membrane?

Accepted Answer

Adenine nucleotide antiporter

Bioenergetics and Free Energy in Biochemical Reactions

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