Carbohydrates

Carbohydrates are polyhydroxy aldehydes and polyhydroxy ketones. Carbohydrates are also known as saccharides (Greek: Sakcharon = sugar). These are classified as follows:

• Monosaccharides

These are the simplest carbohydrates. Their general formula is ( CH₂O )_n , where n= 3 - 7

• Oligosaccharides
  • Disaccharides: give two molecules of same or different monosaccharides. Their general formula is C₁₂H₂₂O₁₁
  • Trisaccharides: give three molecules of same or different monosaccharides. Their general formula is C₁₈H₃₂O₁₆
  • Tetrasaccharides: give four molecules of same or different monosaccharides. Their general formula is C₂₄H₄₂O₂₁

There are few carbohydrates, which give 2-10 molecules of monosaccharides on hydrolysis. On the basis of number of molecules, they are further classified into disaccharides, trisaccharides and tetra saccharides.

• Polysaccharides

Those carbohydrates are termed as polysaccharides which, on hydrolysis, give a large number of monosaccharide molecules. Their general formula is ( C₆H₁₀O₅ )_n ( n =  100 - 3000 ) Monosaccharides and oligosaccharides are crystalline solids, sweet in taste and soluble in water, but polysaccharides are amorphous solids, insoluble in water and tasteless, so they are called non-sugars.

Sugars in everyday life

Monosaccharides: Fructose and glucose occur in sweet fruits and honey. Disaccharides: sucrose in cane sugar or table sugar, maltose in malt (sprouted barley seeds), lactose in milk. Polysaccharides: Amylum in starch, cellulose in cell walls of plants, glycogen (animal starch) in yeast and fungi. It is also present in liver, muscles and brain.

Importance of carbohydrates

Monosaccharides-ribose are important component of DNA and RNA which are responsible for transfer of genetic characters from generation to generation. Ribose is essential component of ATP, the high energy molecules. ATP are called energy currency of the cells. Polysaccharides like starch and glycogen, are reserve food material found in plants (seeds) and animal body (liver and muscles) respectively. Cellulose found in cotton ais used for making clothes. Cellulose found in wood is used for making furniture. Carbohydrates are used in industries asraw materials for paper, textiles etc.