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

Which of the following sugars is not found in plants?

Jute fibres deteriorate quickly because

(1) cellulose content is high

(2) lignin content is high

(3) cellulose content is low

(4) lignin content is low

Vitamin B₆ is also called:-

In a 50 gm living tissue, what would be the amount of water?

1. 15-25 gm

2. 25-30 gm

3. 35-45 gm

4. 70-90 gm

Which of the following elements is present in very less quantity in the body?

1. K             

2. Ca

3. Mg           

4. Cu

Which of the following is a homopolysaccharide?

From the following groups, select the one which has only secondary metabolites?
1. Arbin, cellulose, arginine, tyrosine
2. Glycine, gums, serine, diterpenes
3. Carotenoids, phenylalanine, curcumin, rubber
4. Conclavin-A, morphine, codeine, vinblastine

DNA and RNA comprise of 
1. sugar, phosphate, base
2. sugar, phosphate
3. base, phosphate
4. sugar, base