Most of the CO\(_2\) produced during the catabolism of glucose is released during which stage of cellular respiration?

• A. Lactic acid fermentation
• B. Glycolysis
• C. The citric acid cycle (Krebs cycle)
• D. Oxidative phosphorylation

Answer: (C)

Verified step by step guidance

1. Understand that cellular respiration is the process by which cells break down glucose to produce energy in the form of ATP, and it consists of several stages: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation.
2. Recall that carbon dioxide (CO\(_2\)) is a byproduct of the breakdown of glucose molecules. Specifically, CO\(_2\) is released when carbon atoms are removed from glucose-derived molecules during metabolic reactions.
3. Review the stages of cellular respiration: (1) Glycolysis occurs in the cytoplasm and breaks glucose into two molecules of pyruvate, but no CO\(_2\) is released during this stage. (2) The citric acid cycle (Krebs cycle) occurs in the mitochondrial matrix and involves the complete oxidation of acetyl-CoA, releasing CO\(_2\). (3) Oxidative phosphorylation involves the electron transport chain and ATP synthesis, but it does not release CO\(_2\).
4. Understand that lactic acid fermentation is an anaerobic process that occurs when oxygen is not available. It converts pyruvate into lactate without releasing CO\(_2\), so it is not the stage where most CO\(_2\) is produced.
5. Conclude that the citric acid cycle (Krebs cycle) is the stage of cellular respiration where most of the CO\(_2\) is produced, as it involves the decarboxylation of intermediate molecules, releasing CO\(_2\) as a byproduct.