During which stage of cellular respiration is the majority of carbon dioxide (\(\mathrm{CO_2}\)) produced?

• A. Electron transport chain
• B. Glycolysis
• C. Krebs cycle (citric acid cycle)
• D. Fermentation

Answer: (C)

Verified step by step guidance

1. Understand the process of cellular respiration, which consists of three main stages: glycolysis, the Krebs cycle (citric acid cycle), and the electron transport chain. Fermentation is an alternative pathway under anaerobic conditions.
2. Recall that carbon dioxide (\(\mathrm{CO_2}\)) is produced during the breakdown of glucose and other molecules. This occurs when carbon atoms are removed from molecules as part of metabolic reactions.
3. Review glycolysis: This stage occurs in the cytoplasm and breaks glucose into two pyruvate molecules. No \(\mathrm{CO_2}\) is produced during glycolysis.
4. Examine the Krebs cycle (citric acid cycle): This stage occurs in the mitochondrial matrix. Pyruvate is converted into acetyl-CoA, which enters the cycle. During the cycle, multiple decarboxylation reactions occur, releasing \(\mathrm{CO_2}\) as a byproduct. This is the stage where the majority of \(\mathrm{CO_2}\) is produced.
5. Consider the electron transport chain: This stage occurs in the inner mitochondrial membrane and involves the transfer of electrons to produce ATP. No \(\mathrm{CO_2}\) is produced during this stage.