Biochemistry · Molecule
Glucose !
Glucose is the sugar carried in the blood and the main fuel of the brain and the red blood cells.
Updated 2026-10-31
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Key facts
- A six-carbon aldohexose (C₆H₁₂O₆, 180 g/mol). In solution nearly all of it is a pyranose ring: about two thirds β, one third α.
- Normal fasting plasma glucose: 70–99 mg/dL (3.9–5.5 mmol/L); 126 mg/dL or more on two occasions defines diabetes.
- It enters cells through GLUT carriers (facilitated diffusion) or SGLT (with sodium, in gut and kidney).
- Once phosphorylated to glucose 6-phosphate it is trapped inside the cell.
- Also called
- Dextrose
- Formula
- C₆H₁₂O₆
- PubChem
- CID 64689
Structure
- Carbon 1 (the anomeric carbon) decides whether the ring is α (OH down) or β (OH up); in β every large group is equatorial, the most stable form.
- Less than 1% is open-chain, the aldehyde form that reacts with proteins (glycation).
Clinical notes
- GLUT4 (muscle and fat) moves to the membrane with insulin; its failure is central to insulin resistance.
- HbA1c measures glucose bound to hemoglobin and reflects roughly the past 3 months.
- SGLT2 inhibitors (gliflozins) make the kidney lose glucose in the urine.
Pathways
- Glycolysis
- Gluconeogenesis
- Glycogen metabolism
- Fructose metabolism
- Galactose metabolism
- Lysosomal ganglioside breakdown
Related conditions
Related
Test yourself
Think of the answer, then tap the question to see it.
Which glucose transporter depends on insulin?
GLUT4, in skeletal muscle, heart and fat.
Why can't glucose 6-phosphate leave the cell?
The phosphate makes it negatively charged and there is no carrier to take it out.
What fasting glucose defines diabetes?
126 mg/dL (7.0 mmol/L) or more, confirmed on a second test.
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: beta-D-Glucose (CID 64689) (PubChem, NCBI, 2026) · Public domain; Blood sugar test: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Diabetes (World Health Organization, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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