Solunumu

Solunumu is the set of metabolic processes by which cells extract chemical energy from nutrients to produce ATP, the primary energy currency of the cell. In most organisms it includes glycolysis, pyruvate oxidation, the citric acid cycle (Krebs cycle), and oxidative phosphorylation. In eukaryotic cells these steps occur across the cytoplasm and mitochondria, with oxidative phosphorylation taking place in the inner mitochondrial membrane. Prokaryotes carry out the same general sequence at the plasma membrane or in the cytoplasm.

During glycolysis, which happens in the cytosol, a glucose molecule is split into two pyruvate molecules, yielding a net gain of two ATP and two NADH per glucose. If oxygen is present, pyruvate is transported into mitochondria and converted to acetyl-CoA, releasing CO2 and producing NADH. The acetyl-CoA enters the citric acid cycle, generating ATP (as GTP), NADH, and FADH2 while releasing additional CO2.

Oxidative phosphorylation uses the electrons carried by NADH and FADH2 to drive the electron transport chain in the inner mitochondrial membrane. Electron transfers create a proton gradient that powers ATP synthase to produce most of the cell’s ATP. Oxygen serves as the final electron acceptor, forming water.

In anaerobic conditions, cells can still generate energy by fermentation, such as lactic acid fermentation in animals or alcoholic fermentation in yeast, yielding far less ATP (about 2 per glucose). Solunumu provides the energy required for most cellular activities and is tightly regulated by the cell’s energy and redox state.

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