Polysaccharides: The Long Chain of Simple Sugars

Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide unit bound together by glycosidic linkage. Example: starch, glycogen, cellulose, chitin etc.

Characteristics of polysaccharide

  • On hydrolysis, they yield monosaccharide units which are usually similar.
  • D glucose is the commonest component of polysaccharide.
  • They have high molecular weight.
  • They are usually amorphous, tasteless, nonsugar, insoluble in water.
  • A great majority of carbohydrate of nature occurs in polysaccharide.
  • They do not exhibit any properties of aldehyde or ketone.

Starch

Starch is the most abundant polysaccharide after cellulose. It is a storage product and found in tubers, roots, seeds and other storage organs where it functions as a reserve nutrient for the growth and development of the plant.

Starch content of cereal grains range from 10 to 30% and potatoes from 50 to 70% of dry weight.

Components of starch

Amylose (15-20%) and amylopectin (80-85%) are the two component of starch and these two are polysaccharide themselves.

Source here
Amylose Amylopectin
15-20% of total starch80-85% of total starch
Amylose has a straight chainAmylopectin has a branched chain
Bond among the glucose is 1, 4 typeBoth 1,4 and 1, 6 (to branch out)
Less soluble in waterMore soluble in water
Does not form a gel when hot water is addedForms a gel when hot water is added
Can be hydrolyzed with α amylase and β amylase enzymes completelyCan not be hydrolyzed with α amylase and β amylase enzymes completely
Gives a dark blue or black color when iodine solution is addedGives a reddish brown color when iodine solution is added

 

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About Abulais Shomrat

Abulais Shomrat
Currently in 4th year (Hons) in Department of Botany, University of Dhaka. Planning to have multiple careers one by one but promised to be with 'Plantlet' as long as it's primary stage remains unfinished.

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