250+ TOP MCQs on Mitochondrial Structure and Function – 2 and Answers

Cell Biology Problemson “Mitochondrial Structure and Function – 2”.

1. Glycolysis takes place in _____
A. Outer membrane of mitochondria
B. Inner membrane of mitochondria
C. Mitochondrial matrix
D. Cytosol
Answer: D
Clarification: The process of cellular respiration involves the following steps- Glycolysis, Kreb’s cycle and electron oxidation. The Glycolysis stage occurs in cytoplasm and the Kreb’s cycle occurs in the matrix of mitochondria.

2. The first stable compound of Kreb’s cycle is _____________
A. Citrate
B. Cis- Aconitate
C. Oxaloacetate
D. Malate
Answer: A
Clarification: Kreb’s cycle has Citrate as its first stable compound. That is why it is also called Citric Acid Cycle. Citrate is a compound containing three carboxylic acid groups and it is thus also called Tricarboxylic Acid cycle or TCA cycle.

3. How many ATP molecules are produced per glucose molecules in eukaryotic Glycolysis?
A. 2 ATP
B. 3 ATP
C. 4 ATP
D. 6 ATP
Answer: A
Clarification: The process of cellular respiration involves the following steps- Glycolysis, Kreb’s cycle and electron oxidation, which are involved in energy production by utilizing carbohydrate. Energy is produced in the form of Adenosine triphosphate (ATP) molecules with 2 ATP molecules produced per glucose molecule in Glycolysis.

4. How many ATP molecules are produced per Krebs’ Cycle in eukaryotes?
A. 2 ATP
B. 36 ATP
C. 38 ATP
D. 24 ATP
Answer: D
Clarification: A total of 6 NADH, 2 ATP, and 2 FADH2 molecules are being produced. 3 ATP molecules are produced per NADH molecules. Thus, 18 (6X3) ATP molecules are produced as Krebs’ cycle produces 6 NADH molecules. 1 FADH2 molecule produces 2 ATP, so for 2 FADH2 molecules, 4 ATP molecules are produced. 2 GTP molecules equivalents to 2 ATP molecules produced in Krebs’ cycle. Thus, in one Krebs’ cycle, (18+4+2) = 24 molecules of ATP are produced.

5. After glycolysis, which of the following is transported across the inner mitochondrial membrane into the matrix?
A. Pyruvate
B. Acetyl CoA
C. ATP molecules
D. Coenzyme A
Answer: A
Clarification: Each pyruvate molecule produced in cytosol during Glycolysis is transported across the inner mitochondrial membrane into the mitochondrial matrix. Pyruvate is then decarboxylated to produce Acetyl group (CH₃COO^–) The Acetyl group is transferred to Coenzyme A to produce acetyl CoA.

6. The TCA cycle produces ____________
A. 2 NADH
B. 6 NADH
C. 8 NADH
D. 4 NADH
Answer: B
Clarification: The primary products of the TCA cycle pathway are the reduced coenzymes, NADH and FADH₂, which contain high energy electrons removed from various substrates as they are oxidized. A total of 6 NADH are formed during one Krebs’ cycle process.

7. The TCA cycle produces _____________
A. 2 FADH₂
B. 3 FADH₂
C. 4 FADH₂
D. 1 FADH₂
Answer: A
Clarification: The primary products of the TCA cycle pathway are the reduced coenzymes, NADH and FADH₂, which contain high energy electrons removed from various substrates as they are oxidized. A total of 2 FADH₂ are formed during one Krebs’ cycle process.

8. The TCA cycle produces ___________
A. 2 GTPs
B. 1 GTP
C. 3 GTPs
D. 4 GTPs
Answer: A
Clarification: The primary products of the TCA cycle pathway are the reduced coenzymes, NADH and FADH₂, which contain high energy electrons removed from various substrates as they are oxidized. The Krebs’ cycle produces two GTP molecules during one cycle. 2 GTP molecules equivalents to 2 ATP molecules.

9. In the electron transport chain, each pair of electron transferred from NADH to oxygen releases sufficient energy to produce __________
A. 3 ATPs
B. 1 ATP
C. 2 ATPs
D. 4 ATPs
Answer: A
Clarification: Electron is transported from the reduced cofactor NADH to oxygen by electron transport chain. During the transfer, it releases sufficient energy to drive the formation of approximately 3 ATP molecules.

10. In the electron transport chain, each pair of electron donated by FADH2 releases sufficient energy to produce __________
A. 3 ATPs
B. 1 ATP
C. 2 ATPs
D. 4 ATPs
Answer: C
Clarification: Electron is donated by the reduced cofactor FADH₂ to oxygen by electron transport chain. During the transfer, it releases sufficient energy to drive the formation of approximately 2 ATP molecules.

11. Total number of ATPs formed by oxidation of one glucose molecule is ___________
A. 36 ATPs
B. 30 ATP
C. 32 ATPs
D. 34 ATPs
Answer: A
Clarification: For oxidation of one glucose molecules, 2 ATP molecules are produced by glycolysis. 24 ATP molecules are produced by Kreb’s cycle and 10 ATP molecules is produced by electron oxidative chain. This adds up to 36 molecules ATP released by oxidation of one molecule of glucose.

12. Which of the following is not involved in electron chain transport system?
A. Complexes I, II, II, IV
B. Ubiquinone
C. Cytochrome C
D. All of them are involved
Answer: D
Clarification: Electron carriers can be isolated as part of four distinct, asymmetric, membrane-spanning complexes known as complexes I, II, II and IV. Two of the electron transport chain complexes, Ubiquinone and Cytochrome C are not part of any complexes. Ubiquinone is present as a pool of molecules dissolved in lipid bilayer and Cyt C is soluble protein in intermembrane space.

13. NADH and FADH₂ is associated with respectively ____________
A. Complexes I and complex II
B. Complexes II and complex III
C. Complexes I and complex III
D. Complexes III and complex IV
Answer: A
Clarification: When NADH is the electron donor, electrons enter the respiratory chain via complex I, which transfers electrons to Ubiquinone. FADH₂ remains covalently attached to succinate dehydrogenase, a component of complex II. When FADH₂ is donor, electron is directly passed to Ubiquinone.

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