Glucose

Glucose is a sugar with the molecular formula C6H12O6. The name glucose comes from the Greek word γλευκος, meaning "sweet wine, must". The suffix "-ose" is a chemical classifier, denoting a carbohydrate. It is also known as dextrose or grape sugar. With 6 carbon atoms, it is classed as a hexose, a sub-category of monosaccharides. α- D -glucose is one of the 16 aldose stereoisomers. The D -isomer ( D -glucose) occurs widely in nature, but the L -isomer (L -glucose) does not. Glucose is made during photosynthesis from water and carbon dioxide, using energy from sunlight. The reverse of the photosynthesis reaction, which releases this energy, is a very important source of power for cellular respiration. Glucose is stored as a polymer, in plants as starch and in animals as glycogen.

Glucose is a ubiquitous fuel in biology. It is used as an energy source in most organisms through respiration or fermentation. Glucose is the human body's key source of energy, through aerobic respiration, providing about 3.75 kilocalories of food energy per gram. Breakdown of carbohydrates (e.g. starch) yields mono- and disaccharides, most of which is glucose. Through glycolysis and later in the reactions of the citric acid cycle and oxidative phosphorylation, glucose is oxidized to eventually form CO2 and water, yielding energy mostly in the form of ATP. The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood.

Glucose is a primary source of energy for the brain, so its availability influences psychological processes. When glucose is low, psychological processes requiring mental effort (e.g., self-control, effortful decision-making) are impaired.

