Definition of carbohydrates and classification

Carbohydrate -
         Carbohydrates  are polyhydric alcohol having aldehydes or compounds which yields those derivatives on hydrolysis . Here hydrated carbon is present. Ex-Glucose , Fructose , Starch etc.
Sources of carbohydrate :
Carbohydrates are widely distributed in nature . There are three main sources –
1. Suger : Mono & Disaccharides – Glucose, fructose, galactose , sucrose , lactose etc .
2. Starch : Present in cereals , roots , tuber , plant stems etc.
3. Cellulose : Vegetable , cereals , fibrous lining of fruits .

Carbohydrate

Classification-
Classified into four major groups according to the number of simple sugar unit present in the molecule.
Such as –
1) Monosaccharaides (sugar):
Those carbohydrates which can’t be hydrolyzed further into a simpler from. They contain only one unit of simple sugar Ex- Glucose, Fructose etc.

Monosaccharides are subdivided into –
I. Trioses , tetroses, penoses , hexoses or heptoses according to the number of carbon atom present in the molecule.
II. Aldoses and ketoses , according to the nature of reducing group ( aldehyde or ketone group ) they contain.
2) Disaccharides:
Those which yield two molecules of same or different monosaccharaides when hydrolysed . Ex-sucrose (Glucose + Fructose ) , Maltose ( Glucose+ Glucose). Lactose (glucose + Galactose).
It is of two types :
I. Reducing : Maltose, Lactose.
II. Non –reducing : Sucrose.
III. Oligosaccharides :
Those which yield 2-10 monosaccharaides units on hydrolysis . Ex Rabinose , Raffinose etc.
3) Polysaccharides :
Those which yield an indefinitely large number ( more than 10 molecules) of monosaccharides on hydrolysis. Ex- Starches , dextrins etc.
It is classified –
According to the number of constituents -
i. Pentosans  : Those made up of pentose units. Ex- Inulin .
ii. Hexosans  : Those made up of hexose units. Ex- Starch, dextrin etc.

According to the nature of content –
i. Homo polysaccharides  : When they are made up of some kinds of monosaccharaides. Ex- Starch , dextrin etc.
ii. Heteropolysaccharides : When they are made up of two or more kinds of monosaccharaides or their derivatives. Ex- Munopolysaccharide .