Question 1

Which structural feature of mitochondria is primarily responsible for increasing the surface area available for electron transport and ATP synthesis?

Accepted Answer

Cristae

Question 2

During the citric acid cycle, which enzyme catalyzes the conversion of isocitrate to α-ketoglutarate, producing NADH and releasing CO$_2$?

Accepted Answer

Isocitrate dehydrogenase

Question 3

Which of the following best describes the role of coenzyme Q (ubiquinone) in the electron transport chain?

Accepted Answer

It acts as a mobile electron carrier, transferring electrons between Complex I/II and Complex III.

Question 4

A patient is exposed to cyanide, which inhibits cytochrome c oxidase (Complex IV). What is the most immediate effect on cellular respiration?

Accepted Answer

Electron transport halts, preventing ATP synthesis by oxidative phosphorylation.

Question 5

Which equation correctly represents the highly exergonic reaction catalyzed by Complex IV in the electron transport chain?

Accepted Answer

$2H^+ + 1/2O_2 + 2e^- \rightarrow H_2O$

Question 6

Which of the following statements about the proton motive force (pmf) is correct?

Accepted Answer

It is generated by the active transport of protons from the mitochondrial matrix to the intermembrane space during electron transport.

Question 7

Which of the following best explains why fatty acids yield more ATP per gram than carbohydrates?

Accepted Answer

Fatty acids are more reduced, allowing for more electron extraction during oxidation.

Question 8

In the binding change model of ATP synthase, which conformation of the β subunit is responsible for catalyzing the formation of ATP?

Accepted Answer

T (tight) conformation

Question 9

Which of the following is a correct summary equation for the complete aerobic oxidation of one molecule of glucose?

Accepted Answer

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 38ATP$

Question 10

Which mitochondrial compartment contains the enzymes for the citric acid cycle and β-oxidation of fatty acids?

Accepted Answer

Matrix

Question 11

If the standard reduction potential ($E_0'$) for NAD$^+$ is $-0.32$ V and for O$_2$ is $+0.816$ V, what is the $	riangle E_0'$ for electron transfer from NADH to O$_2$?

Accepted Answer

$+1.136$ V

Question 12

Which of the following is NOT a function of the mitochondrial inner membrane?

Accepted Answer

Phospholipid synthesis

Question 13

Which respiratory complex is directly inhibited by cyanide, leading to cessation of electron transport?

Accepted Answer

Complex IV (cytochrome c oxidase)

Question 14

During β-oxidation of fatty acids, which molecule is produced in each cycle and can enter the citric acid cycle?

Accepted Answer

Acetyl CoA

Question 15

Which of the following statements about mitochondrial DNA is correct?

Accepted Answer

It encodes a small fraction of mitochondrial proteins; most are encoded by nuclear DNA.

Question 16

Which process is responsible for the majority of ATP production in aerobic respiration?

Accepted Answer

Oxidative phosphorylation

Question 17

Which of the following is a direct consequence of the rotation of the γ subunit in ATP synthase?

Accepted Answer

Conformational changes in β subunits that drive ATP synthesis

Question 18

Which of the following best describes the role of cytochrome c in the electron transport chain?

Accepted Answer

It is a small, mobile protein that transfers electrons between Complex III and Complex IV.

Question 19

Which of the following is a correct description of the function of the F$_0$ portion of ATP synthase?

Accepted Answer

It forms a channel for protons to flow from the intermembrane space into the matrix.

Mitochondrial Structure and Cellular Energetics: The Citric Acid Cycle and Oxidative Phosphorylation

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