Cellular respiration produces
Cellular respiration is the process by which cells convert molecules such as glucose into usable energy in the form of adenosine triphosphate (ATP). It occurs in three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle or TCA cycle), and the electron transport chain. Here is a step-by-step breakdown of each stage:
1. Glycolysis: This is the first step of cellular respiration and takes place in the cytoplasm. The process begins with the breakdown of one molecule of glucose into two molecules of pyruvate. Along the way, two molecules of ATP are used, but four molecules of ATP are produced, resulting in a net gain of two ATP. Additionally, two molecules of NADH (nicotinamide adenine dinucleotide) are also produced.
2. Krebs Cycle: After glycolysis, the pyruvate molecules are transported into the mitochondria. Each pyruvate molecule is decarboxylated (carbon dioxide is released) and converted into acetyl-CoA. The acetyl-CoA then enters the Krebs cycle, which occurs in the mitochondrial matrix. During the Krebs cycle, the acetyl-CoA is oxidized, releasing carbon dioxide and generating energy-rich molecules such as NADH and flavin adenine dinucleotide (FADH2). These electron carriers will be used in the next stage.
3. Electron Transport Chain: The final stage of cellular respiration occurs in the inner membrane of the mitochondria, known as the cristae. The NADH and FADH2 molecules produced in the previous steps donate their electrons to the electron transport chain. These electrons move through a series of protein complexes, creating an electrochemical gradient. This gradient drives the synthesis of ATP through a process known as oxidative phosphorylation. At the end of the electron transport chain, the electrons combine with oxygen and protons to form water.
In summary, cellular respiration produces ATP, carbon dioxide, and water as end products. Glycolysis produces a small amount of ATP, while the Krebs cycle and the electron transport chain generate the majority of ATP through oxidative phosphorylation.