NEET UG - Respiration - glycolysis Krebs cycle electron transport chain oxidative phosphorylation Online Test (MCQ Quiz)

1. Which is the first step in the breakdown of glucose during cellular respiration?

A) Electron Transport Chain B) Krebs Cycle C) Glycolysis D) Oxidative Phosphorylation

2. In which part of the cell does glycolysis occur?

A) Mitochondrial matrix B) Cytoplasm C) Thylakoid membrane D) Inner mitochondrial membrane

3. What is the net gain of ATP molecules from one molecule of glucose during glycolysis?

A) 1 ATP B) 2 ATP C) 4 ATP D) 8 ATP

4. Which enzyme catalyzes the committed step in glycolysis?

A) Hexokinase B) Phosphofructokinase-1 C) Pyruvate kinase D) Aldolase

5. What are the end products of glycolysis?

A) Acetyl-CoA and CO2 B) Pyruvate, ATP, and NADH C) Citrate and NADH D) Glucose-6-phosphate and ATP

6. Under anaerobic conditions, pyruvate is converted to lactic acid in which process?

A) Alcoholic fermentation B) Lactic acid fermentation C) Citric acid cycle D) Oxidative phosphorylation

7. In alcoholic fermentation, pyruvate is decarboxylated to form:

A) Ethanol and CO2 B) Lactic acid C) Acetaldehyde D) Oxaloacetate

8. Which molecule links glycolysis to the Krebs cycle?

A) Pyruvate B) Acetyl-CoA C) Citrate D) Oxaloacetate

9. Where does the Krebs cycle (Citric Acid Cycle) take place in eukaryotic cells?

A) Cytoplasm B) Mitochondrial matrix C) Inner mitochondrial membrane D) Outer mitochondrial membrane

10. The Krebs cycle begins with the condensation of acetyl-CoA with which molecule?

A) Malate B) Succinate C) Fumarate D) Oxaloacetate

11. Which of the following is a direct product of the Krebs cycle, besides CO2 and ATP?

A) Pyruvate B) Lactate C) NADH and FADH2 D) Glucose

12. How many molecules of CO2 are released per turn of the Krebs cycle?

A) 1 B) 2 C) 3 D) 4

13. Which enzyme in the Krebs cycle is responsible for the substrate-level phosphorylation of GDP to GTP?

A) Isocitrate dehydrogenase B) Alpha-ketoglutarate dehydrogenase C) Succinyl-CoA synthetase D) Malate dehydrogenase

14. The regeneration of oxaloacetate in the Krebs cycle is crucial for:

A) Generating more ATP B) Continuously accepting acetyl-CoA C) Producing FADH2 D) Releasing CO2

15. Which electron carrier is produced in the Krebs cycle and subsequently used in the Electron Transport Chain?

A) NAD+ B) FAD C) ATP D) ADP

16. The primary role of the Electron Transport Chain (ETC) is to:

A) Synthesize glucose B) Generate ATP by oxidizing NADH and FADH2 C) Break down pyruvate D) Fix carbon dioxide

17. Where is the Electron Transport Chain located in eukaryotic cells?

A) Cytoplasm B) Mitochondrial matrix C) Inner mitochondrial membrane D) Outer mitochondrial membrane

18. Which of the following is NOT a component of the Electron Transport Chain?

A) Ubiquinone B) Cytochrome c C) ATP synthase D) Citrate synthase

19. What is the final electron acceptor in the Electron Transport Chain?

A) Oxygen B) Water C) NADP+ D) ATP

20. The process by which electrons are passed along a series of protein complexes in the ETC is called:

A) Substrate-level phosphorylation B) Oxidative phosphorylation C) Photophosphorylation D) Chemiosmosis

21. Which complex in the ETC pumps protons from the mitochondrial matrix to the intermembrane space?

A) Complex I B) Complex II C) Complex III and IV D) Complex V

22. What is the term for the movement of protons across the inner mitochondrial membrane through ATP synthase?

A) Electron transport B) Oxidative phosphorylation C) Chemiosmosis D) Glycolysis

23. Oxidative phosphorylation directly produces:

A) NADH B) FADH2 C) ATP D) CO2

24. The energy released during the electron transport chain is used to:

A) Reduce NADP+ B) Create a proton gradient C) Synthesize pyruvate D) Regenerate FAD

25. Which molecule is responsible for coupling the proton gradient to ATP synthesis in oxidative phosphorylation?

A) Ubiquinone B) Cytochrome c C) ATP synthase D) Oxygen

26. The 'proton motive force' refers to:

A) The flow of electrons B) The concentration gradient of protons and the electrical potential across the inner mitochondrial membrane C) The synthesis of ATP D) The reduction of oxygen

27. Which of the following statements about the ATP yield from cellular respiration is true?

A) Glycolysis yields more ATP than oxidative phosphorylation. B) The Krebs cycle directly produces a large amount of ATP. C) Oxidative phosphorylation generates the majority of ATP. D) Anaerobic respiration yields more ATP than aerobic respiration.

28. What is the primary role of NADH and FADH2 in cellular respiration?

A) To directly provide energy for cellular work B) To carry electrons to the electron transport chain C) To act as enzymes in the Krebs cycle D) To transport glucose into the mitochondria

29. In prokaryotes, where does the Electron Transport Chain and oxidative phosphorylation occur?

A) Nucleoid region B) Cytoplasm C) Plasma membrane D) Ribosomes

30. Which step in respiration involves the conversion of citrate to isocitrate?

A) Glycolysis B) Pyruvate oxidation C) Krebs cycle D) Electron transport chain

31. The enzyme ATP synthase is also known as:

A) Complex V B) Complex IV C) Succinate dehydrogenase D) Pyruvate dehydrogenase

32. During the oxidation of one molecule of NADH in the ETC, approximately how many protons are pumped across the inner mitochondrial membrane?

A) 4-6 B) 10-12 C) 2-3 D) 1-2

33. The net equation for glycolysis shows that glucose is broken down into:

A) 2 Pyruvate + 2 ATP + 2 NADH B) 2 Pyruvate + 4 ATP + 2 NADH C) 1 Pyruvate + 2 ATP + 2 NADH D) 2 Acetyl-CoA + 2 ATP + 2 NADH

34. Which of the following is a key regulatory enzyme in glycolysis?

A) Aldolase B) Triose phosphate isomerase C) Phosphofructokinase-1 D) Enolase

35. The conversion of pyruvate to acetyl-CoA is catalyzed by the pyruvate dehydrogenase complex and occurs in the:

A) Cytoplasm B) Mitochondrial matrix C) Inner mitochondrial membrane D) Intermembrane space

36. Which complex in the ETC directly receives electrons from FADH2?

A) Complex I B) Complex II C) Complex III D) Complex IV

37. The process of oxidative phosphorylation involves both:

A) Glycolysis and Krebs cycle B) Electron transport chain and chemiosmosis C) Fermentation and glycolysis D) Pyruvate oxidation and substrate-level phosphorylation

38. What happens to the oxygen atoms at the end of the electron transport chain?

A) They are released as CO2 B) They accept electrons and protons to form water C) They are used to synthesize ATP D) They are converted into NAD+

39. Substrate-level phosphorylation occurs during which stage(s) of cellular respiration?

A) Glycolysis and Krebs cycle only B) Krebs cycle and Electron Transport Chain only C) Glycolysis, Krebs cycle, and Electron Transport Chain D) Electron Transport Chain only

40. The complete aerobic respiration of one glucose molecule yields approximately how many ATP molecules?

A) 2-4 B) 10-12 C) 30-32 D) 36-38

41. Which of the following intermediates is part of both glycolysis and the Calvin cycle?

A) Glucose-6-phosphate B) Glyceraldehyde-3-phosphate C) Pyruvate D) Acetyl-CoA

42. The energy released from NADH oxidation in Complex I of the ETC is sufficient to pump how many protons?

A) 4 protons B) 2 protons C) 1 proton D) 0 protons

43. What is the primary function of the Krebs cycle in the context of cellular respiration?

A) To directly produce a large amount of ATP B) To oxidize acetyl-CoA, producing NADH, FADH2, and CO2 C) To regenerate glucose from pyruvate D) To transfer electrons to oxygen

44. Which of the following is a characteristic of anaerobic respiration compared to aerobic respiration?

A) Higher ATP yield per glucose molecule B) Involves the electron transport chain with oxygen as the final acceptor C) Lower ATP yield per glucose molecule D) Complete oxidation of glucose

45. The inner mitochondrial membrane is impermeable to protons, which is essential for:

A) Facilitating the transport of pyruvate B) Allowing the buildup of a proton gradient for ATP synthesis C) Preventing the leakage of electrons D) Carrying out glycolysis

46. Which pathway generates ATP without the involvement of the electron transport chain?

A) Oxidative phosphorylation B) Krebs cycle C) Substrate-level phosphorylation D) Chemiosmosis

47. The 'chemiosmotic hypothesis' explains how ATP is synthesized via:

A) The direct transfer of phosphate from substrate to ADP B) The flow of electrons through membrane proteins C) The coupling of proton gradient energy to ATP synthase activity D) The reduction of oxygen

48. In the overall process of aerobic respiration, the carbon atoms from glucose end up as:

A) Water B) ATP C) Carbon dioxide D) NADH

49. Which enzyme catalyzes the formation of ATP from ADP and Pi using the energy from a proton gradient?

A) Hexokinase B) Pyruvate kinase C) ATP synthase D) Isocitrate dehydrogenase

Respiration - glycolysis Krebs cycle electron transport chain oxidative phosphorylation - Online Test

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