Carbohydrate metabolism



Carbohydrate metabolism denotes the various carbohydrates in living organisms.

The most important carbohydrate is carbon dioxide and water as byproducts.

All carbohydrates share a general formula of approximately CnH2nOn; glucose is C6H12O6. Monosaccharides may be chemically bonded together to form disaccharides such as cellulose.

Carbohydrates are a superior short-term energy reserve for organisms, because they are much simpler to metabolize than fats or triglycerides, and other lipids are commonly used for long-term energy storage. The hydrophobic character of lipids makes them a much more compact form of energy storage than hydrophilic carbohydrates.

Catabolism

Main article: Carbohydrate catabolism

Oligo/polysaccharides are cleaved first to smaller monosaccharides by enzymes called Glycoside hydrolases. The monosaccharide units can then enter into monosaccharide catabolism.

Metabolic pathways

  • Carbon fixation, whereby CO2 is reduced to carbohydrate.
  • ATP and Pyruvate
    • Pyruvate from glycolysis enters the Krebs cycle in aerobic organisms.
  • The NADPH regeneration.
  • Glycogenesis - the conversion of excess glucose into glycogen in order to prevent excessive osmotic pressure buildup inside the cell
  • Glycogenolysis - the breakdown of glycogen into glucose, in order to provide a steady level of glucose supply for glucose-dependent tissues.
  • organic compounds

Glucoregulation

Glucoregulation is the maintenance of steady levels of glucose in the body; it is part of homeostasis, and keeps a constant internal environment around cells in the body.

The hormone insulin makes the body convert glucose into glycogen and puts it into the liver; the insulin is made in the pancreas, and is secreted when the blood sugar is too high. Insulin also promotes the use of glucose by the muscles.

The hormone glucagon, on the other hand, acts in the opposite direction and promotes the conversion of glycogen to glucose in response to low blood sugar.

Human diseases of carbohydrate metabolism

v • d • e
Carbon fixation) Carbohydrate catabolism - Cellular respiration
v • d • e
Carbohydrate metabolism: glycogenesis and Glycogen phosphorylase - Debranching enzyme - Phosphoglucomutase
RegulationPhosphorylase kinase - Phosphoprotein phosphatase
v • d • e
Carbohydrate metabolism: Alanine transaminase
RegulatoryPhosphofructokinase 2/Fructose 2,6-bisphosphatase - Bisphosphoglycerate mutase
v • d • e
Carbohydrate metabolism: fructose and Lactase - Aldose reductase
 
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