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Important Questions CBSE Class 12 Chemistry Chapter 14 – Biomolecules

1.Give some examples of bimolecules

Ans. Examples of biomolecules –

carbohydrates, proteins, Nucleic acids, Lipids, enzymes etc.

2.What are carbohydrates?

Ans. Carbohydrates are optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis.

3.Give one example of each- Monosaccharide, disaccharide and polysaccharide

Ans. Monosaccharide – Glucose, Fructose etc.

Disaccharide – Sucrose, maltose etc.

Polysaccharide – Cellulose, starch etc

4. Which disaccharides are non – reducing sugars?

Ans. In disaccharides, if the reducing groups of monosaccharides, i.e. aldehydic or ketonic groups are bonded eg. In sucrose, these are non- reducing.

5. Classify the following as monosaccharides disaccharides and polysaccharides
Glucose, Sucrose, maltose, ribose, glycogen, lactose, fructose.



6. What is the meaning of statement- Glucose is an aldohexose.

Ans. Glucose is an aldohexose means that it contains six carbon atoms and aldehyde group.

7. Why are polysaccharides considered non- sugars?

Ans. Polysaccharides are not sweet in taste & hence are called non – sugars.

8. Give two examples of reducing sugars

Ans. Examples of reducing sugars –

Maltose   and Lactose.

9. Which sugar is present in milk?

Ans. In milk, lactose is present.

10. Name the reagents used to check the reducing nature of carbohydrates.

Ans. Tollen’s reagent and Fehlings solution can be used to check reducing nature of sugars.

11. Name the different types of RNA molecules found in the cells of organisms

Ans. The different types of RNA molecules are transfer RNA (+ RNA), messenger RNA (m–RNA), ribosomal RNA (r- RNA)

12. What are the three components of nucleic acids?

Ans. The three components of nucleic acid are base, sugar and phosphate group.

13. Name different bases present an (i) DNA (ii) RNA

Ans. Bases present in DNA – Thyamine (T), Adenine (A), Guanine (G), Cytosin (C) and in RNA are uracil (U), Adenine (A), Cytosine (C) and Guanine (G).

14. What is nucleoside?

Ans. The molecules in which one of the organic base is combined with sugar are called nucleosides.

15. What type of bonding occurs between two nucleotides?

Ans. The two nucleotides are joined by phosphodiester linkage.

16. Write the sequence of bases in the complementary strand of the given strand –


Ans. The sequence of bases in the complementary sequence is –


17. Name the various sugars present in RNA & DNA.

Ans. The various sugars present in nucleic acids are Ribose in RNA and deoxyribose in DNA.

18. Write functional differences between RNA & DNA.

Ans. DNA is very important for passing of hereditary information from one generation to other. In RNA protein synthesis takes place.

19. What is the basic unit of proteins?

Ans. The basic unit of all proteins in – amino acids.

20. Give an example of zwitter ion?


21. Write the name of bond between the two – amino acids.

Ans. – amino acids are connected by peptide linkage.

22.What is the information given by primary structure of proteins?

Ans. Primary structure of proteins tells about the sequence in which various amino acids are linked with each other.

23.Name the forces responsible for secondary and tertiary structure.

Ans. The forces which are responsible for tertiary structure of proteins are hydrogen bonds, disulphide linkage, vanderwalls and electrostatic forces of attraction.

24.Which vitamins cannot be stored in our body?

Ans. Water soluble vitamins cannot be stored in our body as they are excreted in urine.

25.Where are fat soluble vitamins like A, D, E, and K stored in our body?

Ans. Fat soluble vitamins are stored in liver and adipose (fat storing) tissues in our body.

26.What are enzymes?

Ans. Enzymes are biocatalyst which are very specific for a particular reaction and a particular   substrate. Almost all enzymes are globular proteins.

27.Where does the water present in the egg go after boiling the egg?

Ans.When an egg is boiled, the proteins present inside the egg get denatured and coagulate. After boiling the egg, the water present in it is absorbed by the coagulated protein through H-bonding.

28. Why cannot vitamin C be stored in our body?

Ans.Vitamin C cannot be stored in our body because it is water soluble. As a result, it is readily excreted in the urine.

29. What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?

Ans. When a nucleotide from the DNA containing thymine is hydrolyzed, thymine -D-2-deoxyribose and phosphoric acid are obtained as products.

30.What are reducing sugars?

Ans. Reducing sugars are carbohydrates that reduce Fehling’s solution and Tollen’s reagent. All monosaccharides and disaccharides, excluding sucrose, are reducing sugars.

31. Write two main functions of carbohydrates in plants.

Ans.Two main functions of carbohydrates in plants are:

(i) Polysaccharides such as starch serve as storage molecules.

(ii) Cellulose, a polysaccharide, is used to build the cell wall.

32. Classify the following into monosaccharides and disaccharides.

Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose

Ans. Monosaccharides: Ribose, 2-deoxyribose, galactose, fructose

Disaccharides: Maltose, lactose


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