Sequence the following stages of cellular respiration:
1. Electron Transport Chain
2. Glycolysis
3. Krebs Cycle
4. Pyruvate Oxidation
Show answer & explanation
Correct answer: A
Explanation
The correct answer is 2 → 4 → 3 → 1.
Stages of Cellular Respiration:
- Cellular respiration is the process by which cells convert glucose into energy (ATP). The correct sequence of its stages is as follows:
- Glycolysis: This occurs in the cytoplasm, where a single molecule of glucose is broken down into two molecules of pyruvate.
- Pyruvate Oxidation: Pyruvate enters the mitochondria and is converted into Acetyl-CoA.
- Krebs Cycle: Also known as the Citric Acid Cycle, this takes place in the mitochondrial matrix and results in the formation of electron carriers such as NADH and FADH₂.
- Electron Transport Chain (ETC): This is the final stage, occurring on the inner mitochondrial membrane, where the majority of ATP (energy) is produced.
Key Points:
- • Location: Glycolysis occurs in the cytoplasm, whereas the other three stages take place within the mitochondria.
- • Energy Yield: The cell derives the greatest amount of energy through the Electron Transport Chain compared to the pyruvate oxidation stage.
- • Anaerobic vs. Aerobic: Glycolysis can be anaerobic, but the remaining stages occur only in the presence of oxygen.
Important Questions for Upcoming Examinations:
- • Question: Where does pyruvate oxidation take place?
- Answer: Mitochondria
- • Question: How many ATP molecules (net gain) are produced from the complete oxidation of a single glucose molecule?
- Answer: Approximately 36 to 38 ATP
- • Question: In which part of the cell does the process of glycolysis occur?
- Answer: Cytoplasm