Medical research

New study reveals important role of insulin in making breast milk

Why do so many mothers have difficulty making enough milk to breastfeed? A new study by scientists at Cincinnati Children's Hospital Medical Center and the University of California Davis adds to their previous research implicating ...

Diabetes

Low-carb diet recommended for diabetics

A new study involving researchers from the University of Alabama at Birmingham and other institutions says patients with Type 1 and Type 2 diabetes should eat a diet low in carbohydrates.

Medical research

How ketogenic diets curb inflammation

Ketogenic diets – extreme low-carbohydrate, high-fat regimens that have long been known to benefit epilepsy and other neurological illnesses – may work by lowering inflammation in the brain, according to new research ...

Diabetes

Diabetics who skip breakfast provoke hazardous blood sugar spikes

More and more Americans on-the-go are skipping the "most important meal of the day," not eating until lunch. This tendency to miss breakfast has already been linked to the growing epidemic of obesity and cardiovascular problems ...

Medical research

Immune system uses gut bacteria to control glucose metabolism

Researchers at Oregon State University and other institutions have discovered an important link between the immune system, gut bacteria and glucose metabolism—a "cross-talk" and interaction that can lead to type 2 diabetes ...

Medical research

Single workout can boost metabolism for days

Lounging around all weekend may weigh heavy on the minds of the health conscious. But these sedentary stretches may not affect the waistline, provided they're preceded by a bit of exercise.

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Carbohydrate metabolism

Carbohydrate metabolism denotes the various biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates in living organisms.

The most important carbohydrate is glucose, a simple sugar (monosaccharide) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of a wide variety of metabolic pathways across species: plants synthesize carbohydrates from atmospheric gases by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids. Plant components are eaten by animals and fungi, and used as fuel for cellular respiration. Oxidation of one gram of carbohydrate yields approximately 4 kcal of energy and from lipids about 9 kcal. Energy obtained from metabolism (eg, oxidation of glucose) is usually stored temporarily within cells in the form of ATP. Organisms capable of aerobic respiration metabolize glucose and oxygen to release energy with carbon dioxide and water as byproducts.

Carbohydrates are a superior short-term fuel for organisms because they are simpler to metabolize than fats or those amino acid portions of proteins that are used for fuel. In animals, the most important carbohydrate is glucose; so much so, that the level of glucose is used as the main control for the central metabolic hormone, insulin. Starch, and cellulose in a few organisms (eg, termites, ruminants, and some bacteria), being both glucose polymers are disassembled during digestion and absorbed as glucose. Some simple carbohydrates have their own enzymatic oxidation pathways, as do only a few of the more complex carbohydrates. The disaccharide lactose, for instance, requires the enzyme lactase to be broken into into its monosaccharides components; many animals lack this enzyme in adulthood.

Carbohydrates are typically stored as long polymers of glucose molecules with Glycosidic bonds for structural support (e.g. chitin, cellulose) or for energy storage (e.g. glycogen, starch). However, the strong affinity of most carbohydrates for water makes storage of large quantities of carbohydrates inefficient due to the large molecular weight of the solvated water-carbohydrate complex. In most organisms, excess carbohydrates are regularly catabolised to form Acetyl-CoA, which is a feed stock for the fatty acid synthesis pathway; fatty acids, 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. However, animals, including humans, lack the necessary enzymatic machinery and so do not synthesize glucose from lipids. <ref, G Cooper, The Cell, American Society of Microbiology, p 72>

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

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