Cellulose is largely present in plant cells and is the most abundant carbohydrate present in nature. It forms the basis of vegetable fibres such as cotton and jute.
Dextrins give a red colour with iodine.
Dextrins are produced when starch is partially hydrolysed. This is carried out by acid or enzyme amylase. Dextrins produced from amylose have unbranched chains, whereas those produced from amylopectin have branched chains (refer Figure 2.14). Dextrins are soluble in water and get precipitated by alcohol. They have a sweet taste. Figure 2.14 Structure of Dextrin
Dextrins are present in all starch-producing plants. They are also present in honey and are the important constituents of various foods. They are used as adhesives and binders.
Glycogen shows a deep red colour with iodine.
Glycogen has a branched structure as well. It is a polymer consisting of D-glucose units. The glucose units in the linear structure are joined by α(1 → 4) glycosidic linkages and branching occurs via α(1 → 6) linkages (Figure 2.13). The branching point occurs at every eight to ten α-D-glucose units. This type of linkage…
Occurrence Glycogen is the storage form of polysaccharide present in animals (muscle and liver). Glycogen in the liver is catabolised to glucose and transferred via blood stream to the tissue for the energy purpose. Glycogen in the muscle acts as a good source of energy.
The basic unit of starch is glucose. It is composed of two units, namely amylase (15%–35%) and amylopectin (65%–85%). The structure of amylose looks like a long helically coiled unbranched chain of glucose molecules connected by α(1 → 4) linkages. The molecular weight of amylase is between 10,000 and 1,00,000. Amylose gives a deep blue…
Starch Occurrence Starch is a polysaccharide that is largely present in the plant kingdom. The most common sources are cereals, grains, potatoes, carrots, millets, and legumes.
Polysaccharides produce more than twelve molecules of monosaccharide units on hydrolysis. The molecular formula is (C6H10O5)n. Polysaccharides are classified into two types: