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Biochemistry · Small molecule

Glucose 3D Structure

The main sugar fuel of cells: six carbons, five of them closed into a ring with an oxygen, and a hydroxyl group on almost every carbon.

Glucose is the main fuel carried in the blood and the starting point of glycolysis. In water almost all of it is a six-membered ring, which forms when the oxygen at carbon 5 bonds to carbon 1. This is beta-D-glucose, the form with the hydroxyl at carbon 1 on the same side as carbon 6, which makes up about two thirds of glucose in solution.

Also called β-D-glucose, Dextrose or Blood sugar.

Beta-D-glucose as balls and sticks: a six-membered ring of five carbons and one oxygen in a chair shape, with hydroxyl groups and a CH2OH group pointing out round its edge.
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A ring of six atoms

Glucose, C6H12O6, is a hexose: a sugar with six carbons. In water nearly every molecule is in a ring form; well under one in a hundred is the open chain that textbooks often draw first.

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View 1 of 5: A ring of six atoms

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The Glucose structure, explained

  1. 01A ring of six atoms

    Glucose, C6H12O6, is a hexose: a sugar with six carbons. In water nearly every molecule is in a ring form; well under one in a hundred is the open chain that textbooks often draw first.

  2. 02A chair, not a flat hexagon

    The ring of five carbons and an oxygen puckers into a chair, the shape that keeps its bonds at their natural angles. Drawn flat, as a Haworth projection, it hides this shape.

  3. 03How the ring closes

    In the open chain, carbon 1 is an aldehyde. The hydroxyl oxygen of carbon 5 bonds to it, and the aldehyde oxygen becomes a new hydroxyl on carbon 1. The ring can open and close again in water, which is how alpha and beta change into each other.

  4. 04Beta: carbon 1's hydroxyl

    In beta-D-glucose the hydroxyl on carbon 1 sits on the same side of the ring as carbon 6. In alpha it sits on the other side. Starch and glycogen are built of alpha glucose; cellulose is built of beta glucose, and human enzymes cannot break its links.

  5. 05Every group points outwards

    In the chair of beta-D-glucose, every hydroxyl and the CH2OH group points outwards round the ring's edge, in equatorial positions, where they crowd each other least. This makes beta-D-glucose unusually stable among sugars.

Parts

What each part does

Pyranose ring
Five carbons and one oxygen in a six-membered ring, named after pyran. It is not flat but puckered into a chair.
Ring oxygen
The oxygen that was the hydroxyl of carbon 5 in the open chain. Bonding to carbon 1 closes the ring.
Carbon 1, the anomeric carbon
The carbon that was the aldehyde of the open chain. It carries the hydroxyl that decides alpha or beta, and it is the carbon that forms glycosidic bonds to other sugars.
Hydroxyl groups
Five OH groups, one on every carbon except carbon 5, which holds the ring oxygen. They form hydrogen bonds with water, which is why glucose dissolves so well.
Carbon 6
The CH2OH group outside the ring. In D-glucose drawn in the usual way it points up, and beta means the hydroxyl at carbon 1 points up too.

The structure

Where these atoms come from

Compound
PubChem CID 64689
Formula
C₆H₁₂O₆
Molar mass
180.16 g/mol
Atoms shown
24, hydrogens included
IUPAC name
(2R,3R,4S,5S,6R)-6-(hydroxymethyl)oxane-2,3,4,5-tetrol
InChIKey
WQZGKKKJIJFFOK-VFUOTHLCSA-N

Coordinates from PubChem's computed 3D model, in the public domain. The model is one low-energy shape of the molecule; in water it flexes and turns about its single bonds.

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Sources

Where the facts come from

Written by biofideX from these sources. Drawn with 3Dmol.js (Rego and Koes, Bioinformatics 2015).

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