Q: What is the overall reaction catalyzed by Complex I in the electron transport chain?

$\text{NADH} + 5\text{H}^+_{\text{matrix}} + \text{Q} \rightarrow \text{NAD}^+ + \text{QH}_2 + 4\text{H}^+_{\text{intermembrane space}}$

Q: Which equation correctly represents the reaction catalyzed by Complex II?

$\text{FADH}_2 + \text{Q} \rightarrow \text{FAD} + \text{QH}_2$

Question 1

Which molecule acts as a lipid-soluble electron carrier in the electron transport chain and can carry two electrons?

Accepted Answer

Quinone

Question 2

What is the correct sequence of electron flow in the mitochondrial electron transport chain starting from NADH?

Accepted Answer

NADH $\rightarrow$ Complex I $\rightarrow$ CoQ $\rightarrow$ Complex III $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O$_2$

Question 3

Which of the following statements about cytochromes in the electron transport chain is correct?

Accepted Answer

Cytochromes contain porphyrin rings with Fe and can carry one electron.

Question 4

What is the overall reaction catalyzed by Complex I in the electron transport chain?

Accepted Answer

$	ext{NADH} + 5	ext{H}^+_{	ext{matrix}} + 	ext{Q} ightarrow 	ext{NAD}^+ + 	ext{QH}_2 + 4	ext{H}^+_{	ext{intermembrane space}}$

Question 5

Which complex in the electron transport chain does NOT pump protons across the mitochondrial membrane?

Accepted Answer

Complex II

Question 6

A patient has a genetic defect in Complex IV of the electron transport chain. Which of the following consequences is most likely?

Accepted Answer

Decreased ATP production due to impaired electron transfer to oxygen

Question 7

Which of the following best describes the role of FADH$_2$ in oxidative phosphorylation?

Accepted Answer

It donates electrons to Complex II, which then transfers them to CoQ.

Question 8

Which equation correctly represents the reaction catalyzed by Complex II?

Accepted Answer

$	ext{FADH}_2 + 	ext{Q} ightarrow 	ext{FAD} + 	ext{QH}_2$

Question 9

During oxidative phosphorylation, which molecule is the final electron acceptor?

Accepted Answer

O$_2$

Question 10

Which of the following is a correct description of the function of Complex III?

Accepted Answer

Transfers electrons from QH$_2$ to cytochrome c and pumps protons

Question 11

If a drug blocks the transfer of electrons from cytochrome c to Complex IV, what would be the immediate effect?

Accepted Answer

Accumulation of reduced cytochrome c

Question 12

Which of the following is TRUE regarding the proton gradient generated by the electron transport chain?

Accepted Answer

It is used to drive the synthesis of ATP via ATP synthase.

Question 13

A mutation causes Complex I to lose its ability to transfer electrons to CoQ. Which of the following would most likely occur?

Accepted Answer

Decreased ATP production and increased NADH levels

Question 14

Which of the following reactions occurs at Complex IV?

Accepted Answer

$4	ext{Cyt c}_{	ext{red}} + 8	ext{H}^+_{	ext{matrix}} + 	ext{O}_2 ightarrow 4	ext{Cyt c}_{	ext{ox}} + 2	ext{H}_2	ext{O} + 4	ext{H}^+_{	ext{intermembrane space}}$

Question 15

Which of the following best explains why oxygen is essential for oxidative phosphorylation?

Accepted Answer

Oxygen acts as the final electron acceptor, allowing the electron transport chain to continue.

Question 16

Which of the following would most likely result from inhibition of Complex III?

Accepted Answer

Decreased proton gradient and reduced ATP synthesis

Question 17

Which molecule is responsible for shuttling electrons from Complex III to Complex IV?

Accepted Answer

Cytochrome c

Question 18

In a patient with mitochondrial disease affecting the inner membrane, which process would be most directly impaired?

Accepted Answer

Oxidative phosphorylation

Question 19

Which of the following is a correct summary of the role of quinones in the electron transport chain?

Accepted Answer

They are lipid-soluble molecules that transfer electrons between Complex I/II and Complex III.

Question 20

Which of the following is a direct consequence of electron flow through the electron transport chain?

Accepted Answer

Generation of a proton gradient across the inner mitochondrial membrane

Oxidative Phosphorylation: Electron Transport Chain and ATP Synthesis

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