Starch is a colourless and odourless polysaccharide that is found in plants as stored carbohydrates. It is a polymer of glucose monomers that are linked with each other to form a polysaccharide.
Starch is composed of two types of polysaccharide molecules:
- Amylose
- Amylopectin
Amylose and Amylopectin
Amylose is a polysaccharide made of several D-glucose units. They are linked by 1,4-glycosidic bonds. When iodine is added to starch, the colour changes to dark blue or black due to the presence of amylose present in the starch. Amylose is soluble in water and can be hydrolyzed into glucose units by the enzymes α- amylase. They are linked by α(1→4) glycosidic bonds. Amylase catalyses the hydrolysis of starch into sugars. Amylose in starch is responsible for giving the deep blue colour in the presence of iodine. Iodine gets trapped in the amylose helices.
Amylopectin is a polymer of several D-glucose molecules. 80% of amylopectin is present in starch. Amylopectin molecules are linked by α-1,4-glycosidic bonds and α-1,6-glycosidic bonds. It is a water-insoluble fraction.
Heating starch with water produces a colloidal suspension due to the swelling of starch granules. It readily dissolves in hot water. On cooling, it forms a starch paste or starch gel.
Let us discuss the difference between amylose and amylopectin.
Also Read: Carbohydrates
Difference Between Amylose and Amylopectin
Following are the important difference between amylose and amylopectin:
Amylose | Amylopectin |
It is a straight-chain polymer of D-glucose units | It is a branched-chain polymer of D-glucose units |
Constitutes 20% of starch | Constitutes 80% of starch |
It is soluble in water | It is insoluble in water |
Straight chain structure | Branched structure |
It contains α-1,4-glycosidic bonds between two glucose units | It contains α-1,4-glycosidic bonds between two glucose units in the straight chain and α-1,6-glycosidic bonds at the branching |
Also Read: Difference between Osmosis and Diffusion
Thus we see how amylose and amylopectin are different from each other. For more information on the difference between the two, keep visiting BYJU’S website or download BYJU’S app for further reference.
What are the changes expected if the amylopectin content far exceeds that of amylose in starch
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