Carbohydrates

=Carbohydrates=


 * Carbohydrates** are a family of organic compounds with the general chemical formula (CH2O)//n// where //n// is the number of carbons in the molecule. They are one of the major families of biopolymers and their range of biological uses is diverse: as metabolic substrates and intermediates; as structural components in DNA and RNA; and as cellular recognition molecules such as the antigens of red blood cells.

Carbohydrates range in size from the single sugar molecules, or **monosaccharides**, to two or a few chemically-bonded sugars, **disaccharides** or **oligosaccharides**, respectively, through to multiple sugars linked together in high-molecular weight chains called **polysaccharides**. As is frequently the case in bio-polymerisation, monosaccharides are joined to form larger structures by condensation; i.e. water is lost in the formation of a bond. They may conversely be split apart by the addition of water, or hydrolysis. The bond which holds together adjacent sugar molecules is a **glycosidic bond.**

Carbohydrates are oxidised alcohols. In fact, all carbohydrates can be derived from the oxidation of glycerol, C3H5(OH)3. In all carbohydrates there is one carbon atom that is most heavily oxidised and this constitutes either the ketone or aldehyde functional group of the molecule.

The general structure of a ketone group is drawn below. The family of carbohydrates that contain this chemical group are called ketoses.



The general structure of an aldehyde group is now drawn below. The family of carbohydrates that contain this chemical group are called aldoses.



In carbohydrate nomenclature, it is also important to state the number of carbon atoms in the molecule. For instance, glucose (C6H12O6) contains 6 carbon molecules and is thus known as a //hexose// sugar. Because its functional group is an aldehyde, it might fully be called an //aldohexose//. Dihydroxyacetone (C3H6O3) has 3 carbon atoms and a ketone functional group, and is thus referred to as a //ketotriose//.

As mentioned above, all carbohydrates can be obtained from the oxidation of glycerol. Glycerol, though not a carbohydrate itself, might be seen as the 'parent molecule' of carbohydrates. Glycerol may be oxidised to provide glyceraldehyde - with an aldehyde functional group - or dihydroxyacetone - with a ketone functional group. These molecules are the only aldotriose and ketotriose, respectively, and may be viewed as the simplest molecules in each respective family of carbohydrates.