The first step of cellular respiration is known as glycolysis. This process takes place in the cytoplasm of the cell and is essential for breaking down glucose, which is a primary source of energy for cells.
During glycolysis, one molecule of glucose, which is a six-carbon sugar, is split into two molecules of pyruvate, a three-carbon compound. This conversion requires energy, which is initially invested in the form of ATP (adenosine triphosphate). Specifically, two ATP molecules are used to initiate the process.
As glycolysis progresses, energy is released, and four ATP molecules are produced through substrate-level phosphorylation. Additionally, two molecules of NADH, a carrier of electrons, are generated. NADH plays a crucial role in later stages of cellular respiration by carrying electrons to the electron transport chain.
In summary, glycolysis is a vital metabolic pathway that not only provides the basic energy units in the form of ATP but also prepares the products for the next steps of cellular respiration, which include the citric acid cycle and oxidative phosphorylation.