noun, plural: aldoses
A carbohydrate is an organic compound consisting of carbon, hydrogen, and oxygen. Carbohydrates are classified into monosaccharides, disaccharides, oligosaccharides, polysaccharides, and heterosaccharides. The monosaccharides are the simplest forms of carbohydrates. They may be further classified based on the carbonyl group they contain. Accordingly, monosaccharides may be aldose or ketose. An aldose is a monosaccharide that contains an aldehyde group (-CHO) whereas a ketose is one that contains a ketone (C=O).
An aldose has a general chemical formula of Cn (H2O) n. Aldoses may be grouped further based on the number of carbons in the main chain. A three-carbon aldose is referred to as triose. An example is the triose glyceraldehyde, which is also the simplest aldose. A four-carbon carbohydrate is called a tetrose. Examples of tetrose aldoses are erythrose and threose. A five-carbon carbohydrate is called a pentose and five-carbon aldoses are ribose, arabinose, xylose, and lyxose. A six-carbon carbohydrate is called a hexose and an example of an aldohexose is glucose, which is also one of the most commonly known aldose.
Aldoses may occur as either in d- or in l- form.