Question

animals (including humans) breathe in air containing oxygen and breathe out air with less oxygen and more carbon dioxide. the carbon dioxide comes from __________. i dont know yet fermentation pyruvate oxidation and the citric acid cycle glycolysis the electron transport chain

Explanation:

In cellular respiration, during pyruvate oxidation and the citric acid cycle (also known as the Krebs cycle), carbon dioxide is produced. Glycolysis produces pyruvate but no carbon dioxide. Fermentation does not produce carbon dioxide in animals (it produces lactic acid). The electron transport chain uses oxygen as the final electron acceptor but does not directly produce carbon dioxide from the breakdown of organic molecules in the way pyruvate oxidation and the citric acid cycle do.

Answer:

pyruvate oxidation and the citric acid cycle