Carbohydrates

CARBOHYDRATES

Organic compounds with a general formula (CH2O)n
Carbohydrates can be classified into 3 categories,
(1) Monosaccharides
(2) Oligosaccharides
(3) Polysaccharides

(1) Monosaccharides

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,

(b) Ketoses

(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.

(2) Oligosaccharides

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.

(3) Polysaccharides

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