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Class 10 Class 12
Draw the structure of amino acid.

Amino acid are organic compounds made up of carbon, hydrogen, oxygen and nitrogen. They consist of an amino group and an acidic group attached to the the same carbon called α-carbon. Thus, they are also known as α-amino acids. They are substituted methanes. Four groups occupy the four valency positions. The four groups being an amino group, a hydrogen, A carboxylic group and a variable R group. The R group could be a hydrogen(the amino acid is called glycine), a methyl group (alanine) etc. There are 20 amino acids that occur in proteins.


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

The different tests are

(a) For proteins - Biuret's test. If Biuret’s reagent is added to protein,and the colour of the reagent changes from light blue to purple it shows the presence of protein.

(b) For fats or oils - Grease and solubility of the test. 

(c) For amino acids - Ninhydrin test. If Ninhydrin reagent is added to the solution, then the colourless solution changes to pink, blue, or purple, it shoes the presence of amino acids. 

On testing the fruit juice, saliva, sweat and urine for the molecules we get the following result.

Substance Biuret's test for protein Grease or solubulity test for fats and oil Ninhydrin test for amino acids.
1. Fruit juice Gives positive result showing the presence of proteins.  Negative result showing absence of fats and oils.  Gives positive result for the presence of amino acids.  
2. Saliva Shows presence of proteins Absence of fats and oils Shows presence of amino acids.
3. Sweat Absence of proteins Presence of fats or opils Absence of amino acids
4. Urine  Presence of proteins. Not present Presence of amino-acids.


Illustrate a glycosidic, peptide and a phosphodiester bond.

(1) Glycosidic - Monosaccharides in a polysaccharide chain are linked by a glycosidic bond. The bond is formed between two carbon atoms of two adjacent monosaccharides with loss of a water molecule. 

(2) Peptide bond: Amino acids in a polypeptide or protein are linked by a peptide bond, which is formed when the carboxyl group ie. COOH of one amino acid reacts with the amino (–NH2) group of the next amino acid with the elimination of a water molecule . 

(3) Phosphodiester bond : In a nucleic acid the phosphate group and sugar are joined together by phosphodiester bonds. An bonds is formed between phosphate and pentose sugar molecule in a nucleotide. The bond is called phosphodiester bond because there is an ester bond on either side. 


Describe the important properties of enzymes. 

The important properties of enzymes are: 

1. All enzymes are proteins. They are complex macromolecules with high molecular weight.

2.  They catalyse 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. They catalyse reactions at a high rate with the help of the active site. They lower down the activation energy and thus the reaction can proceed with ease. 

4.  Enzymes do not initiate a reaction but accelerate it. 

5. They are not used up in the reaction. 

6. Enzymes affect the rate and not the direction.

7. Most of the enzymes have a high turnover number that is the number of molecules of a substance that is acted upon by an enzyme per minute. 

8. Enzymes are specific in action.

9. Enzymatic activity is affected by changes in temperature, pH and concentration of the substrate.



Find and write down structure of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.

Structual formulae for ten small molecules. Find and write down structure of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.


Purines and pyrimidines are manufactured by isolation. They are used by various laboratories, hospitals and research centres.


Explain composition of triglyceride.

The triglycerides are made up of glycerol and three fatty acids. It is an ester of glycerol and fatty acids. The three fatty acids present in the triglycerides, may be same or different.