Final answer:
Cellular respiration includes three main stages: glycolysis, the Krebs cycle, and electron transport. In the Krebs cycle, pyruvate from glycolysis is converted into acetyl CoA which then enters the cycle in the mitochondria, yielding ATP and reducing NAD to NADH while producing carbon dioxide.
Step-by-step explanation:
Stages of Cellular Respiration
Cellular respiration is a multi-stage metabolic pathway by which living cells harvest energy from organic compounds, primarily glucose. The process can be divided into three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle), and electron transport (the third stage).
In the presence of oxygen, pyruvate, which is produced from glucose during glycolysis, is transformed into an acetyl group attached to coenzyme A to form acetyl CoA. This occurs in the matrix of the mitochondrion, where the acetyl CoA delivers the acetyl group to oxaloacetate, forming citrate, and enters the Krebs cycle. It's here during this cycle that carbon dioxide is produced, and molecules like NADH are formed, which will later donate electrons to the electron transport chain for ATP synthesis.
The complete process sees the original glucose molecule fully oxidized into carbon dioxide and water, with the storage of chemical potential energy in the form of ATP and electron carriers like NADH and FADH2. Glycolysis occurs in the cytoplasm, while the Krebs cycle and electron transport require oxygen and occur within the mitochondria.