Biology Class 11 NCERT Solutions: Chapter 9 Biomolecules Part 4

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Q: 12. What are gums made of? Is Fevicol different?

Answer:

Gums are hetero-polysaccharides. They are made from two or more different types of monosaccharides. On the other hand, fevicol is polyvinyl alcohol (PVA) glue. It is not a polysaccharide.

Q: 13. Find out a qualitative test for proteins, fats and oil, amino acids and test any fruit juice, saliva, sweat, and urine for them.

Answer:

(A) Test for protein

Biuret's test - If Biuret's reagent is added to protein, then the colour of the reagent changes from light blue to purple.

(B) Test for fats and oils

Grease or solubility test

(C) Test for amino acid

Ninhydrin test - If Ninhydrin reagent is added to the solution, then the colourless solution changes to pink, blue, or purple, depending on the amino acid.

Ninhydrin Test
Ninhydrin test on various food

Item

Name of the test

Procedure

Result

Inference

1.

Fruit Juice

Biuret’s test

Fruit Juice + Biuret’s reagent

Colour changes from light blue to purple

Protein is present.

Grease test

To a brown paper, add a few drops of fruit juice.

No translucent spot

Fats and oils are absent or are in negligible amounts.

Ninhydrin test

Fruit juice + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour

Amino acids are present.

2.

Saliva

Biuret’s test

Saliva + Biuret’s reagent

Colour changes from light blue to purple

Proteins are present

Grease test

On a brown paper, add a drop of saliva.

No translucent spot

Fats/oils are absent.

Ninhydrin test

Saliva + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour

Amino acids are present.

3.

Sweat

Biuret’s test

Sweat + Biuret's

reagent

No colour change

Proteins are absent.

Solubility test

Sweat + Water

Oily appearance

Fats/oil may be present.

Ninhydrin test

Sweat + Ninhydrin reagent + boil for 5 minutes

No colour change, solution remains colourless

Amino acids are present.

4.

Urine

Biuret’s test

Few drops of urine + Biuret’s reagent

Colour changes from light blue to purple

Proteins are present.

Solubility

Few drops of urine +water

Little bit of oily appearance

Fats may or may not be present.

Ninhydrin test

Few drops of urine + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour depending on the type of amino acid

Amino acids are present.

Q: 14. Find out how much cellulose is made by all the plants in the biosphere and compare it with how much of paper is manufactured by man and hence what is the consumption of plant material by man annually. What a loss of vegetation!

Answer:

Approximately, billion tonnes of cellulose are made per year by all the plants in the biosphere and it takes full-grown trees to make one ton of paper. Trees are also used to fulfil the other requirements of man such as for timber, food, medicines, etc. Hence, it is difficult to calculate the annual consumption of plant material by man.

Q: 15. Describe the important properties of enzymes.

Answer:

Properties of enzymes

(1) Enzymes are complex macromolecules with high molecular weight.

(2) They catalyze biochemical reactions in a cell. They help in the breakdown of large molecules into smaller molecules or bring together two smaller molecules to form a larger molecule.

(3) Enzymes do not start a reaction. However, they help in accelerating it.

(4) Enzymes affect the rate of biochemical reaction and not the direction.

(5) Most of the enzymes have high turnover number. Turnover number of an enzyme is the number of molecules of a substance that is acted upon by an enzyme per minute. High turnover number of enzymes increases the efficiency of reaction.

(6) Enzymes are specific in action.

(7) Enzymatic activity decreases with increase in temperature.

(8) They show maximum activity at an optimum of .

(9) The velocity of enzyme increases with increase in substrate concentration and then, ultimately reaches maximum velocity.

Image shows the Properties of enzymes

Image Shows the Properties of Enzymes

Image shows the Properties of enzymes