Cellular respiration is a biochemical process by which cells convert nutrients, primarily glucose, into adenosine triphosphate (ATP), the primary energy currency of the cell. This process involves a series of metabolic reactions that occur in different parts of the cell, primarily within the mitochondria in eukaryotic cells.
Cellular respiration can be divided into three main stages:
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Glycolysis: This process occurs in the cytoplasm and involves breaking down one molecule of glucose into two molecules of pyruvate. It generates a small amount of ATP and NADH (a carrier of electrons).
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Krebs Cycle (Citric Acid Cycle): This takes place in the mitochondria and further processes the pyruvate into carbon dioxide while producing electron carriers (NADH and FADH2) and a small amount of ATP.
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Electron Transport Chain: Also occurring in the mitochondria, this stage uses the electrons from NADH and FADH2 to create a proton gradient across the mitochondrial membrane, ultimately producing a large quantity of ATP through oxidative phosphorylation. Oxygen serves as the final electron acceptor, forming water as a byproduct.
Cellular respiration can occur in both aerobic (with oxygen) and anaerobic (without oxygen) conditions. In aerobic respiration, glucose is fully oxidized to carbon dioxide and water, while in anaerobic respiration, processes like fermentation take place, yielding less energy.
Overall, cellular respiration is essential for providing the energy needed for various cellular activities and maintaining life in organisms.