In RNA thymine is replaced by

1. uracil                           

2. adenine

3. thiamine                       

4. guanine

The vitamin nicotinamide can be synthesized in our body from.

1. tyrosine

2. tryptophan

3. valinc

4. phenylalanine

An example of the competitive inhibition of an enzyme is the inhibition of:

1. succinic dehydrogenase by malonic acid

2. cytochrome oxidase by cyanide

3. hexokinase by glucose -6-phosphate

4. carbonic anhydrase by carbondioxide

In which one of the following sets of three items each belong to the category mentioned against them?

(1) Lysine, glycine, thiamine - amino acids

(2) Myosin, oxytocin and gastrin -hormones

(3) Rennin, helicase and hyaluronidase - enzymes

(4) Optic nerve, oculomotor, vagus - sensory nerves

The figure given below shows three velocity substrate concentration curves for an enzyme reaction. What do the curves a, b,  and c depict respectively?

(1) a - normal enzyme reaction

     b - competitive inhibition

     c - non-competitive inhibition

(2) a - enzyme with an allosteric modulator added

     b - normal enzyme activity

     c - competitive inhibition

(3) a - enzyme with an allosteric stimulator

     b - competitive inhibition added

     c - normal enzyme reaction

(4) a - normal enzyme reaction

     b - non-competitive inhibitor added

     c - allosteric inhibitor added

Which of the following contain $\mathrm{\beta }$-1, 4 linkage?

(1) Maltose

(2) Sucrose

(3) Lactose

(4) Fructose

Enzymes, vitamins and hormones can be classified into a single category of biological chemicals because of all of these

(1) enhance oxidative metabolism

(2) are conjugated proteins

(3) arc exclusively synthesised in the body of a living organism as at present

(4) help in regulating metabolism.

Cut surfaces of fruit and vegetables often become dark because

(1) dirty knife makes it dark

(2) oxidation of tannic acid in the presence of a trace of iron from the knife makes it dark

(3) dust of the air makes it dark

(4) none of the above

Cotton fibres mainly contains

(1) cellulose           

(2) glycogen

(3) protein             

(4) lipid

Which of the following sugars is not found in plants?

(1) Sucrose

(2) Glucose

(3) Lactose

(4) Fructose