Glucose

Glucose, a simple monosaccharide sugar, is one of the most important carbohydrates and is used as a source of energy in animals and plants. Glucose is one of the main products of photosynthesis and starts respiration. The natural form (D-glucose) is also referred to as dextrose, especially in the food industry.

Role in metabolism

Carbohydrates are the human body's key source of energy, providing 4 calories (17 kilojoules) of food energy per gram. Breakdown of carbohydrates (e.g. starch) yields mono- and disaccharides, most of which is glucose.

Related Topics:
Calories - Kilojoule - Food energy - Gram - Starch

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Through glycolysis, glucose is directly involved in the production of ATP, the cell's energy carrier. In addition, it is critical in the production of protein and in lipid metabolism. As the central nervous system does not metabolise lipids, it is more dependent on glucose than other tissues.

Related Topics:
Glycolysis - ATP - Cell's - Protein - Lipid - Central nervous system

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Glucose is absorbed into the bloodstream through the intestinal wall. Only the mono-saccharides glucose, fructose and galactose are absorbed in humans; these are the end-products of the digestion of carbohydrates. The glucose and galactose are absorbed via a Sodium-dependent transporter protein into the intestinal cell (GLUT-2).

Related Topics:
Bloodstream - Intestinal wall - Fructose - Galactose

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Some of this glucose goes directly to fuel brain cells, while the rest makes its way to the liver and muscles, where it is stored as glycogen ("animal starch"), and to fat cells, where it is stored as fat. Glycogen is the body's auxiliary energy source, tapped and converted back into glucose when it needs more energy. Although stored fat can also serve as a backup source of energy, it is never directly converted into glucose. The fructose and galactose are taken up by the liver, where they are converted into glucose.

Related Topics:
Brain cells - Liver - Muscles - Glycogen - Fat cells - Fat

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