Carbohydrate Structure Monosaccharides Disaccharides

thumb Glucose as a straight-chain carbohydrate thumb Fructose Pure carbohydrates contain carbon, hydrogen, and oxygen atoms, in a 1:2:1 molar ratioIn algebra, a ratio is the relationship between two quantities. It is expressed as the quotient of one magnitude divided by another, or as a relation between several variables. Examples: If a school has a twenty-to-one student-teacher ratio, that means th, giving the general formulaA formula is a concise way of expressing information symbolically (as in a mathematical or chemical formula) or a general relationship between quantities. A famous one is Albert Einstein's E m × c 2 (see Special relativity). See also WikiMath: how to writ C_xH_2xO_x. However, many important carbohydrates deviate from this, such as deoxyriboseDeoxyribose (more fully 2-deoxyribose is a five- carbon sugar (a pentose) derived from the pentose sugar ribose by the repacement of the hydroxyl group at the 2 position with hydrogen, leading to the net loss of an oxygen. Ribose forms a five member ring. Sometimes compounds containing other elements are also counted as carbohydrates (e.g. chitinIn biology, chitin is one of the main components in the cell walls of fungi, the exoskeleton of insects and other arthropods, and in some other animals. It is a polysaccharide, made out of units of acetylglucosamine (more completely, N-acetyl-D-glucos-2-a, which contains nitrogenNitrogen is the chemical element in the periodic table that has the symbol N and atomic number 7. A common normally colorless, odorless, tasteless and mostly inert diatomic non-metal gas, nitrogen constitutes 78 percent of Earth's atmosphere and is a cons).

The simplest carbohydrates are monosaccharideMonosaccharides are carbohydrates in the form of simple sugars. Monosaccharides, like disaccharides, are sweet, water soluble and crystalline. Monosaccharides are classified by the number of carbon atoms they contain ( triose, tetrose, pentose, hexose ands, which are small straight-chain aldehydeAn aldehyde is either a functional group consisting of a terminal carbonyl group, or a compound containing a terminal carbonyl group. Where -R represents the carbon chain. Structure The aldehyde functional group is a carbonyl group bonded to a hydrogen ats and ketoneA ketone is either the functional group characterized by a carbonyl group linked to two other carbon atoms or a compound that contains this functional group. A ketone can be generally represented by the formula: :R( C O)R. A carbonyl carbon bonded to twos with many hydroxyl groups added, usually one on each carbon except the functional group. Other carbohydrates are composed of monosaccharide units, and break down under hydrolysis. These may be classified as disaccharides, oligosaccharides, or polysaccharides, depending on whether they have two, several, or many monosaccharide units.

2 Monosaccharides

Monosaccharides may be divided into aldoses, which have an aldehyde group on the first carbon atom, and ketoses, which typically have a ketone group on the second. They may also be divided into trioses, tetroses, pentoses, hexoses, and so forth, depending on how many carbon atoms they contain. For instance, glucose is an aldohexose, fructose a ketohexose, and ribose an aldopentose.

Further, each carbon atom that supports a hydroxyl group (except for the first and last) is optically active, allowing a number of different carbohydrates with the same basic structure. For instance, galactose is an aldohexose, but has different properties from glucose because the atoms are arranged differently.

A heterocyclic form of ribose

The straight-chain structure described here is only one of the forms a monosaccharide may take. The aldehyde or ketone group may react with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal , in which case there is an oxygen bridge between the two carbon atoms, forming a heterocyclic ring. Rings with five and six atoms are called furanose and pyranose forms, and exist in equilibrium with the straight-chain form.

It should be noted that the ring form has one more optically active carbon than the straight-chain form, and so has both an alpha and a beta form, which interconvert in equilibrium. However, the carbohydrate may further react with an alcohol to form an acetal or ketal , in which case the two forms become distinct. This is the basic type of link between the monosaccharide units of larger carbohydrates.

3 Disaccharides

Disaccharides are composed of two monosaccharide units bound together. The binding between the two sugars results in the loss of a hydrogen atom (H) from one molecule and a hydroxyl group (OH) from the other.

The most common disaccharides are sucrose (cane or beet sugar - made from one glucose and one fructose), lactose (milk sugar - made from one glucose and one galactose) and maltose (made of two glucoses). The formula of these disaccharides is C₁₂H₂₂O₁₁.

4 Nutrition

Refined grain products are rich sources of complex carbohydrates

Strictly speaking, carbohydrates are not necessary for human nutrition because proteins can be converted to carbohydrates - the traditional diet of some peoples consists of nearly zero percent carbohydrate, and they are perfectly healthy. However, they require (relatively) less water to digest than proteins or fats, and are an important source of energy.

Problems have been cited for the long term effects of a no-carbohydrate diet. These include reduced athletic performance, possible brain damage, and nephrotoxicity. The brain can only utilize carbohydrates for energy, and protein may not supply enough in many cases. The increase in protein means that more ammonia groups need to be removed from the blood.

Home > Carbohydrate

1 Structure

2 Monosaccharides

3 Disaccharides

4 Nutrition

5 Catabolism

6 See also

7 External links

Topics: Carbohydrate, Structure, Monosaccharides, Disaccharides...