PPT On Carbohydrates
Carbohydrates Presentation Transcript:1. INTRODUCTION
The name Carbohydrates indicates that they are hydrates of Carbon, and contain carbon, hydrogen and oxygen. Most of them contain hydrogen and oxygen in the ratio of 2:1. For that reason, the general empirical formula of carbohydrates is given as [C(H2O)]n e.g,glucose is (C6H12O6) carbohydrates may be defined as Polyhydroxy aldehyde or Ketone or substances that yield these on hydrolysis.e.g.glucose is a polyhydroxy aldehyde and fructose is a polyhydroxy ketone. The names of carbohydrates often end in the suffix-ose.
The carbohydrates often termed as Sugars,are the “staff of life” for most organisms. Carbohydrates are also known as Saccharides(Sakcharon=sugar or sweetness). They are widely distributed molecules in both plant and animal tissues. They are indispensable for living organisms,serving as skeletal structures in plants and also in insects and crustaceans. They also occur as food reserves in the storage organs of plants and in liver and muscles of animals. In addition,they are an important source of energy required for the various metabolic activities of the living organisms;the energy being derived as a result of their oxidation.
3. CLASSIFICATION OF CARBOHYDRATES
The naturally occurring carbohydrates may be classified into three main groups,particularly on the basis of their behaviour towards hydrolysis. Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group,the number of carbon atoms it contains, and its chiral handedness. If the carbonyl group is an aldehyde,the monosaccharide is an aldose; if the carbonyl group is ketone;the monosaccharide is a ketose.Monosaccharide with three carbon atoms are called trioses,those with four are called tetroses,five are called pentoses,six are called hexoses.
They are the simplest sugars and cannot be hydrolysed into simpler compounds. Their general formula is CnH2nOn,where n varies from 3to7.The most important are the pentoses and hexoses.
On hydrolysis they generally yield 2 to 9 molecules of monosaccharides which are sugars and include di-, tri-tetrasaccharides etc. The monosaccharides are joined together by glycosidic bonds. glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The most abundant are the disaccharides, which consist of two monosaccharide units.
Polysaccharides are the carbohydrates which yield a large number of monosaccharides on hydrolysis. They contain greater than ten monosaccharide units.
7. REACTION OF MONOSACCHARIDES
Monosaccharides possess some characteristic properties due to the presence of some specific groups,namely aldehydic,alcoholic,alchol-aldehydic,and α-glycolic. Oxidation with acids: With mild oxidants(like HOBr):-Only the aldehyde group is oxidized to produce monocarbolic acids.Ketoses,however don’t respond to this reaction.Hence reaction is used to distinguish aldoses from ketoses.
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