Diabetes

Researchers investigate hormonal links between diet and obesity

Obesity is a growing public health crisis, bringing with it many serious risk factors, including cardiovascular disease and type 2 diabetes. As the number of people who are either overweight or obese now outnumbers those ...

Health

Vitamin C can shorten the length of stay in the ICU

Vitamin C administration shortened the length of stay in the intensive care unit on average by 8 percent in 12 trials with 1766 patients according to a meta-analysis published in Nutrients.

Medical research

Micro-control of liver metabolism

Researchers at TIFR have discovered molecular anticipation of feeding in the liver that is essential to ensure that the body, after fasting, adapts to use incoming nutrients upon re-feeding. Their findings, published in the ...

Immunology

Scientists stumble upon a model to study a lethal complication

More and more hospitalized patients with sepsis are being diagnosed with a deadly complication characterized by high levels of inflammation. A team of Yale researchers has uncovered clues to the cause of this complication—which ...

Cancer

Study overturns dogma of cancer metabolism theory

Scientists at the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA have discovered that squamous cell skin cancers do not require increased glucose to power their development and growth, ...

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.

Genetics

A look at how colds and chronic disease affect DNA expression

We're all born with a DNA sequence that encodes (in the form of genes) the very traits that make us, us—eye color, height, and even personality. We think of those genes as unchanging, but in reality, the way they are expressed, ...

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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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