Organic compounds with a general formula (CH2O)n
Carbohydrates can be classified into 3 categories,
Trioses: Trioses are simple sugars derived from hydrolysis of oligopolysaccharides.
have ‘C’ atom ranging from 3-9 (eg.)
They are of two types
(a)Aldoses: Sugars with terminal CHO aldehyde group aldotriose- Glyceraldehyde (simplest sugar).
- Aldoterose-Erythrose, thresose
- Aldopentose – Arabiose ribose deoxyribose
- Aldohexose – Glucose, galactose, mannose
(b)Ketoses: Having >C=O group
- Ketotriose – Dihydroxy acetone – simplest keto sugar
- Ketohexose – Fructose – It is the sweetest among all the sugars.
All derived from combination of two or more monosaccharides units Depending upon the number of monosaccharides presence they can be classified as
(I) Disaccharides: eg. Sucrose, Maltose, Lactose, cellobiose
(II) Trisaccharides: eg. Raffinose
(III) Teirasaccharides: eg. Stachyose
Sucrose: Produced from alpha glucose beta fructose by alpha. –1.2. glycosidic linkage. It is a Non- reducing sugar.
Maltose: Consists of 2 units of glucose linked together by alpha 1.4 linkage reducing sugar found in germinating seeds largely.
Cellobiose: Consists of 2 units of glucose but the bond involved is beta, 1.4 linkage. It is a reducing sugar.
Lactose: Consists of one molecule of beta D glucose and one molecule of beta D galactose linked together by beta 1.4 linkages.
Stachyose: It is a tetra saccharide consists of one glucose and one fructose and 2 galactose.
Molecular weight in kilo Daltons (kd)
(a) Storage polysaccharides:
In plant consists of amylase, amylopectin. (It is polymer of glucose).
Amylase: Amylase is un-branched chains of glucose units joined by alpha – 1.4 linkages. The chain is nonlinear, but it is helical one.
Amylopectin: It is highly branched, Bond types: Alpha-1.4 linkage but at the branching points alpha 1.6 linkage is present.
Glycogen: It is present only in animal cells. It is just like starch, but heavily branched and compact and it contains both alpha 1.4 and alpha 1.6 linkages.
(b) Structural Polysaccharides
Cellulose: Polymer of glucose joined together by beta 1.4 linkage