Glucose is a monosaccharide that is used as a main source of energy in a living cell. Oxidation of glucose results in the formation of ATP and reduced NADH that transfers electrons to the respiratory chain in the mitochondria. The electrons are required for the formation of the proton gradient involved in the synthesis of more ATP molecules. ATP is used in multiple metabolic processes, including synthesis of proteins, nucleic acids, and other biomolecules, as well as is involved in multiple signaling and transport processes in a cell. As a result, glucose is a water-soluble compound that is the major source of energy in the body, specifically, the central nervous system and erythrocytes.