Notes On Carbohydrates: Disaccharides - CBSE Class 12 Chemistry
Disaccharides are formed from two monosaccharides, covalently linked together. The hydrolysis of a disaccharide may yield two molecules of the same or different monosaccharides. The three important disaccharides are sucrose, maltose and lactose.
 

 
The bond between two monosaccharides is called a glycosidic linkage or a glycosidic bond.  The two monosaccharides are joined together through an oxygen atom.
 
   
 
Sucrose:
 
Sucrose is obtained from sugarcane or sugar beets.  It has the chemical formula, C12H22O11
 

 
Sucrose is made up of one unit of glucose — specifically, the alpha anomer alpha D glucopyranose — and one unit of fructose — specifically, the beta anomer beta D fructofuranose. Sucrose gives a negative test with sucrose gives a negative test with reagents. Hence, sucrose is called a non-reducing sugar.
  
Maltose:
 
Maltose is another important disaccharide, which contains two glucose units.
 
    
                 
Lactose:
 
Lactose is a disaccharide present in milk
 

 
Lactose is made from beta-D-galactose and beta-D-glucose

Summary

Disaccharides are formed from two monosaccharides, covalently linked together. The hydrolysis of a disaccharide may yield two molecules of the same or different monosaccharides. The three important disaccharides are sucrose, maltose and lactose.
 

 
The bond between two monosaccharides is called a glycosidic linkage or a glycosidic bond.  The two monosaccharides are joined together through an oxygen atom.
 
   
 
Sucrose:
 
Sucrose is obtained from sugarcane or sugar beets.  It has the chemical formula, C12H22O11
 

 
Sucrose is made up of one unit of glucose — specifically, the alpha anomer alpha D glucopyranose — and one unit of fructose — specifically, the beta anomer beta D fructofuranose. Sucrose gives a negative test with sucrose gives a negative test with reagents. Hence, sucrose is called a non-reducing sugar.
  
Maltose:
 
Maltose is another important disaccharide, which contains two glucose units.
 
    
                 
Lactose:
 
Lactose is a disaccharide present in milk
 

 
Lactose is made from beta-D-galactose and beta-D-glucose

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