By B.T. Alo, updated March 24, 2022
Glucose (C6H12O6), also known as grape sugar or blood sugar, is a primary product of photosynthesis and the central energy currency of living organisms. As a monosaccharide carbohydrate, it forms the backbone of more complex polysaccharides such as starch and glycogen.
Glucose is composed of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.
Carbon—the fourth most abundant element in the universe—constitutes the skeletal framework of all life. Each glucose molecule contains six carbon atoms arranged in a linear chain. One of these carbons is bonded to a formyl group, giving glucose the classification of an aldohexose. Carbon is integral to glycolysis and the citric acid cycle, where it is sequentially oxidized to release ATP.
Hydrogen, the lightest element, makes up 12 atoms in glucose. Though it does not bond directly to elemental carbon, the C–H bonds in organic molecules like glucose provide the necessary structural stability. Hydrogen bonding also dictates the stereochemistry of glucose, determining whether it is a D‑ or L‑sugar; only the D‑form is biologically active.
Oxygen, the third most abundant element after hydrogen and helium, supplies six atoms per glucose molecule. Oxygen atoms participate in the aldehyde group and various hydroxyl groups, enabling glucose oxidation during aerobic respiration to produce CO₂ and H₂O.
Image credit: simpson33/iStock/GettyImages
