What are three major stages that must occur in order for glucose to be converted to carbon dioxide and water in aerobic conditions?

To understand the three major stages involved in the conversion of glucose to carbon dioxide and water in aerobic conditions, we need to explore the process called cellular respiration. Cellular respiration is a metabolic pathway that occurs in the cells of living organisms to generate energy from glucose. It involves three primary stages: Glycolysis, Krebs cycle (also known as the Citric Acid Cycle or TCA cycle), and the Electron Transport Chain (ETC).

1. Glycolysis:
Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm of the cell. In this step, glucose (a six-carbon molecule) is broken down into two molecules of pyruvate (a three-carbon molecule) in ten enzymatic reactions. Glycolysis results in a small net gain of ATP and the production of NADH, a high-energy electron carrier. Although glycolysis occurs in anaerobic conditions, it is a necessary step in both aerobic and anaerobic respiration processes.

2. Krebs Cycle (Citric Acid Cycle or TCA cycle):
The Krebs cycle occurs in the mitochondria's matrix, and it converts the pyruvate molecules, produced during glycolysis, into carbon dioxide and energy-rich molecules (NADH and FADH2). Each pyruvate molecule is decarboxylated to form acetyl-CoA, which enters the Krebs cycle. Through a series of enzymatic reactions, acetyl-CoA is gradually oxidized, generating energy carriers such as NADH and FADH2 and releasing carbon dioxide as a byproduct.

3. Electron Transport Chain (ETC):
The Electron Transport Chain takes place in the inner mitochondrial membrane. It is the final stage of aerobic respiration and is responsible for the majority of energy production. During this process, the high-energy electrons carried by NADH and FADH2 are transported through a series of protein complexes, which create a proton gradient across the mitochondrial membrane. The flow of protons back into the mitochondrial inner space through ATP synthase leads to the production of ATP. In the final step of the Electron Transport Chain, oxygen acts as the final electron acceptor, combining with protons to form water (H2O).

Overall, these three stages together convert glucose to carbon dioxide and water, generating a considerable amount of ATP along the way. The breakdown of glucose in aerobic conditions through cellular respiration allows cells to efficiently produce energy for various biological processes.