What is the first stage of cellular respiration?

The first stage of cellular respiration is glycolysis. In this process, glucose, a six-carbon sugar, is broken down into two three-carbon molecules of pyruvate. This transformation occurs in the cytoplasm of the cell and does not require oxygen, making it an anaerobic process. Glycolysis involves a series of enzymatic reactions that also produce a small amount of ATP and NADH, which are crucial for energy transfer and further stages of cellular respiration.

After glycolysis, the pyruvate molecules can enter the next stages of cellular respiration, which include the citric acid cycle and oxidative phosphorylation, but glycolysis itself lays the foundation by initiating the breakdown of glucose and generating key energy-carrying molecules. This step is fundamental for both aerobic and anaerobic respiration pathways.