Differentiate between the following:
(i) Amylose and amylopectin
(ii) Peptide linkage and glycosidic linkage
(iii) Fibrous proteins and globular proteins
OR
Write the chemical reactions to show that open structure of D-glucose contains the following:
(i) Straight chain
(ii) Five alcohol groups
(iii) Aldehyde as carbonyl group
Amylose
(i) Straight chain polymer
(ii) Test with iodine shows blue stains
(iii) 20% water soluble
Amylopectin
(i) Branched chain polymer
(ii) Iodine test shows re-brown stains.
(iii) 80-85% water solubility
(iv) has 1-4 glycosidic linkage
(iv) Has α -1,4 and α-1,6-glycosidic linkage.
Peptide linkage
(i) The proteins are linked by peptide bond.
(ii) It consists of ─CONH2─ bond between two molecules.
(iii) Hydrolysis of peptide bond gives two amino acids
Glycosidic linkage
(i) Monosaccharides are linked by glycosidic bond
(ii) The molecules are bonded by (─O─) link.
(iii) Hydrolysis gives two Monosaccharides.
Fibrous proteins
(i) Has linear poly-peptide chain arrangement
(ii) Insoluble in water, e.g. myosin
Globular proteins
(i) Coil arrangement of peptide chains.
(ii) Soluble n water, e.g. albumins, insulin
OR
D-glucose is obtained from hydrolysis or decomposition of sucrose by enzyme invertase. It has a straight chain, five alcohol groups and aldehyde as a carbonyl group as seen in the structure given below:
(i) the reaction of reduction of alcohol groups which results into hexane justifies the straight chain in the structure
(ii) Formation of penta-acetate when treatment with acetic anhydride suggests the presence of 5 alcohol groups.
(iii) Mild oxidation of glucose leads to formation of gluconic acid which can be detected using neutralisation in a basic medium.
