Can someone explain at what point during cellular respiration glucose is completely oxidized?
Thanks.
Sure! During cellular respiration, glucose is completely oxidized at the end of the electron transport chain (ETC) that occurs in the inner mitochondrial membrane. The ETC is the last step of cellular respiration and takes place after glycolysis and the Krebs cycle.
To understand at what point glucose is completely oxidized, let's break down cellular respiration into its three major stages:
1. Glycolysis: This is the initial step where glucose is broken down in the cytoplasm of the cell. During glycolysis, glucose is partially oxidized and split into two molecules of pyruvate. At this stage, only a small portion of the energy stored in glucose is released, mainly in the form of ATP and NADH.
2. Krebs cycle: After glycolysis, each pyruvate enters the mitochondria. In the Krebs cycle (also known as the citric acid cycle or TCA cycle), the pyruvate molecules are further broken down, releasing more energy in the form of ATP, NADH, and FADH₂. However, at this stage, glucose is not yet fully oxidized.
3. Electron transport chain (ETC): The final stage of cellular respiration is the ETC. This process occurs within the inner mitochondrial membrane. NADH and FADH₂, produced in the previous stages, donate their high-energy electrons to the ETC. As electrons move through a series of protein complexes in the ETC, energy is released and used to pump protons (H⁺ ions) across the inner mitochondrial membrane, creating an electrochemical gradient. This gradient drives ATP synthesis by ATP synthase.
At the end of the ETC, oxygen acts as the final electron acceptor, combining with electrons and protons to form water (H₂O). This means that glucose is completely oxidized to carbon dioxide (CO₂) during the electron transport chain. The energy released from glucose oxidation throughout cellular respiration is used to generate a total of 36-38 ATP molecules.
To summarize, glucose is completely oxidized to CO₂ during the electron transport chain, which is the final step of cellular respiration.