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 starch 80-85% of total starch
Amylose has a straight chain Amylopectin has a branched chain
Bond among the glucose is 1, 4 type Both 1,4 and 1, 6 (to branch out)
Less soluble in water More soluble in water
Does not form a gel when hot water is added Forms a gel when hot water is added
Can be hydrolyzed with α amylase and β amylase enzymes completely Can not be hydrolyzed with α amylase and β amylase enzymes completely
Gives a dark blue or black color when iodine solution is added Gives 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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