Chemical Reactions; Carbohydrate Qualitative Analysis

Chemical Reactions:
Carbohydrate Qualitative Analysis
Skills to build:
? Doing microscale reactions
? Observing evidence of a chemical reaction
? Using chemical reactions to identify a carbohydrate
? Identifying reducing sugars
? Identifying aldoses and ketoses
? Identifying pentoses

Introduction:
Along with proteins and fats, carbohydrates, or sugars, are one of the three main classes of food used to sustain life. They are essential components of all living organisms and constitute the most abundant class of biological molecules. The classification carbohydrate stems from the general molecular formula for monosaccharides, (C·H2O)n where n > 3, which implies that these compounds are hydrates of carbon. However, carbohydrates are not true hydrates in the chemical sense.
Carbohydrates, chemically, are polyhydroxy aldehydes (?CHO) or ketones (C=O) or compounds which upon hydrolysis yield these compounds. Note that each carbon in a polyhydroxy aldehyde or ketone structure, except for the carbonyl functional group (in yellow), bears a hydroxyl (?OH) functional group (in green). Polyhydroxy aldehydes and ketones with the same number of carbons are structural isomers of each other.Carbohydrates may be classified based upon the number of polyhydroxy aldehyde or ketone (saccharide) units found in their structure. The basic carbohydrate
unit is a single polyhydroxy aldehyde or ketone, or monosaccharide. A disaccharide can be viewed as two monosaccharides from which water is removed to join the units. The bond that forms between the two sugar units is known as a glycosidic bond or linkage. Oligosaccharides consist of 3-10 sugar units covalently joined together, and
polysaccharides are large biomolecular polymers of covalently bonded monosaccharide units.