Final answer:
The carbon dioxide exhaled during cellular respiration is produced during the preparatory reaction, which converts pyruvate to acetyl CoA, and the citric acid cycle, where acetyl CoA is further oxidized to CO2. The correct answer is 'a. preparatory reaction and citric acid cycle'.
Step-by-step explanation:
During cellular respiration, the carbon dioxide that you exhale originates mainly from two key stages: the preparatory reaction and the citric acid cycle (also known as the Krebs cycle or TCA cycle). These stages are part of the aerobic processes that occur within the mitochondria in the presence of oxygen. Glycolysis, which is the initial stage of cellular respiration, generates pyruvate that undergoes a transformation where it loses a carbon molecule as CO2 during the preparatory reaction, becoming acetyl CoA. This acetyl CoA then enters the citric acid cycle, where each acetyl group is further oxidized to CO2.
Therefore, the correct answer to the question is 'a. preparatory reaction and citric acid cycle'. The preparatory reaction converts pyruvate into acetyl CoA with the loss of one carbon dioxide per pyruvate molecule. Subsequently, during the citric acid cycle, the remaining carbons from the original glucose molecule are released as carbon dioxide through a series of chemical reactions. The electron transport chain is primarily involved in the production of ATP and does not directly release carbon dioxide.a. preparatory reaction and citric acid cycle.