<unk>  denotes the various biochemical processes responsible for the formation, breakdown and interconversion of<unk> s in living organisms.
The most important<unk>  is glucose, a simple sugar (monosaccharide) that is metabolized by nearly all known organisms. Glucose and other<unk> s are part of a wide variety of metabolic pathways across species: plants synthesize<unk> s from atmospheric gases by photosynthesis, which can then be consumed by other organisms and used as fuel for cellular respiration. Oxidation of one gram of<unk>  yields approximately 4 kcal of energy. Energy obtained from<unk>  is usually stored in the form of ATP. Organisms capable of aerobic respiration metabolize glucose and oxygen to release energy with carbon dioxide and water as byproducts.
All<unk> s share a general formula of approximately CnH2nOn; glucose is C6H12O6. Monosaccharides may be chemically bonded together to form disaccharides such as sucrose and longer polysaccharides such as starch and cellulose.<unk> s are a superior short-term energy reserve for organisms, because they are much simpler to metabolize than fats or proteins. In animals, all dietary<unk> s are delivered to cells in the form of glucose.<unk> s are typically stored as long polymers of glucose molecules with Glycosidic bonds for structural support (e.g. chitin, cellulose) or energy storage (e.g. glycogen, starch). However, the strong affinity of<unk> s for water makes storage of large quantities of<unk> s inefficient due to the large molecular weight of the solvated water-carbohydrate complex. In some organisms, excess<unk> s are catabolised to form Acetyl-CoA, where they enter the fatty acid synthesis pathway. Fatty acids, triglycerides, and other lipids are commonly used for long-term energy storage. The hydrophobic character of lipids makes them a much more compact form of energy storage than hydrophilic<unk> s.
Carbohydrate metabolism
Drug metabolism
Fatty acid metabolism
Cell signaling
Energy transformation
Photosynthesis
Signal transduction
Cellular respiration