(a) Write the product when D - glucose reacts with Br₂ (aq).

(b) What type of bonding provides stability to - helix structure of protein?

(c) Name the vitamin whose deficiency causes pernicious anaemia.

OR

Define the following terms:

(a) Invert Sugar

(b) Native Protein

(c) Nucleotide

(a) D-glucose gets oxidised to six carbon carboxylic acid called gluconic acid on reaction with a mild oxidising agent like bromine water.

(b) Hydrogen bonding provides stability to - helix structure of protein.

A polypeptide chain forms all possible hydrogen bonds by twisting into a right handed screw (helix) with the –NH group of each amino acid residue hydrogen bonded to the C=O of an adjacent turn of the helix.

(c) Deficiency of vitamin B₁₂ causes pernicious anaemia.

OR

(a) Sucrose is dextrorotatory but after hydrolysis gives dextrorotatory glucose and laevorotatory fructose. Since the laevorotation of fructose (–92.4°) is more than dextrorotation of glucose (+52.5°), the mixture is laevorotatory. Thus, hydrolysis of sucrose brings about a change in the sign of rotation, from dextro (+) to laevo (–) and the product is named as invert sugar.

(b) Protein found in a biological system with a unique three dimensional structure and biological activity is called a native protein.

(c) When nucleoside is linked to phosphoric acid at 5′-position of sugar moiety, we get a nucleotide. It consists of phosphate, pentose sugar and nitrogenous base as shown in figure.