Metabolic Pathway Resulting in the Formation of CO2

There are several metabolic pathways in living organisms that result in the formation of carbon dioxide (CO2). One such pathway is cellular respiration, which occurs in the mitochondria of eukaryotic cells. Cellular respiration involves the breakdown of glucose and other organic molecules to produce energy in the form of ATP, with CO2 being released as a byproduct.

Cellular Respiration
1. Glycolysis: The first step of cellular respiration is glycolysis, which takes place in the cytoplasm. Glucose, a six-carbon molecule, is converted into two molecules of pyruvate, a three-carbon molecule. This process generates a small amount of ATP and NADH.

2. Pyruvate Decarboxylation: The next step occurs in the mitochondria. Each pyruvate molecule is transported into the mitochondrial matrix, where it undergoes decarboxylation. This process removes a carbon atom from each pyruvate molecule in the form of CO2, resulting in the formation of acetyl-CoA, a two-carbon molecule. Additionally, NADH is produced during this step.

3. Citric Acid Cycle (Krebs Cycle): Acetyl-CoA enters the citric acid cycle, a series of reactions that occur in the mitochondrial matrix. During this cycle, acetyl-CoA is completely oxidized, releasing two molecules of CO2 per cycle. Additionally, NADH and FADH2 are generated, which carry high-energy electrons to the electron transport chain.

4. Electron Transport Chain (ETC): The ETC is located in the inner mitochondrial membrane. NADH and FADH2 from the previous steps donate their electrons to the ETC. As electrons pass through the ETC, ATP is produced through oxidative phosphorylation. Oxygen serves as the final electron acceptor, combining with hydrogen ions to form water. This ensures the continuous flow of electrons through the ETC.

5. CO2 Release: As the citric acid cycle and ETC continue, two more molecules of CO2 are released per glucose molecule. These CO2 molecules are formed during the decarboxylation steps of the citric acid cycle. Ultimately, the complete oxidation of one glucose molecule through cellular respiration results in the release of six molecules of CO2.

Conclusion
Cellular respiration is a metabolic pathway that results in the efficient production of ATP. During this process, glucose is broken down through glycolysis and the citric acid cycle, releasing CO2 as a byproduct. The CO2 is formed during the decarboxylation steps of pyruvate and the citric acid cycle. The energy stored in glucose is converted into ATP, which is essential for various cellular activities.