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Biomolecules | Chemistry - Short Answer Questions | 12th Chemistry : UNIT 14 : Biomolecules

Chapter: 12th Chemistry : UNIT 14 : Biomolecules

Short Answer Questions

Chemistry : Biomolecules : Book Back Questions, Answers, Solutions: Short Answer Questions

Biomolecules | Chemistry

Short Answer Questions

1. What type of linkages hold together monomers of DNA?

a) Hydrogen bonding between complementary base pairs

b) Base-stacking interactions

2. Give the differences between primary and secondary structure of proteins.


1. Linear polypeptide chain

2. Only peptide bond between amino acids .


1. Two different polypeptide chain (α-helix, β-Heated)

2. In addition to the peptide bond, hydrogen bonding also observed.


3. Name the Vitamins whose deficiency cause i) rickets ii) scurvy

i) Rickets - Vitamin D

ii) Scurvy - Vitamin C

4. Write the Zwitter ion structure of alanine

5. Give any three difference between DNA and RNA


• It is mainly present in nucleus, mitochondria and chloroplast

• It contains deoxyribose sugar

• Base pair A = T. G ≡ C

• Double stranded molecules

• It can replicate itself


• It is mainly present in cytoplasm, nucleolus and ribosomes

• It contains ribose sugar

• Base pair A = U. C ≡ G

• Single stranded molecules

• It cannot replicate itself. It is formed from DNA.


6. Write a short note on peptide bond

The carboxyl group of the one amino acid react with the amino group of the another amino acid to give an amide linkage between amino acids. This amide linkage is called peptide bond.

7. Give two difference between Hormones and vitamins


• It is secreted by tissues in our body

• It induces a physiological response


• It cannot be synthesised by our body

• It is essential for the normal growth and maintenance of our health.


8. Write a note on denaturation of proteins

The process of a protein-losing its higher order structure without losing the primary structure, it is called denaturation. When a protein denatures, its biological function is also lost.

Each protein has a unique three- dimensional structure formed by interactions such as disulphide bond, hydrogen bond, hydrophobic and electrostatic interactions.

These interactions can be disturbed when the protein is exposed to a higher temperature, certain chemicals such as urea, alteration of pH, ionic strength etc.,

9. What are reducing and non – reducing sugars?

Reducing sugars

If the carbonyl group in the sugars are not involved in the glycosidic linkage then they retain their reducing property such sugars are called non-reducing sugars.

Eg: Lactose

Non-reducing sugars

If the carbonyl group in the sugars are involved in the glycosidic linkage then they are not available for reduction such sugars are called reducing sugars.

Eg: Sucrose


10. Why carbohydrates are generally optically active.

Carbohydrates are having chiral centres. Hence they are optically active

11. Classify the following into monosaccharides, oligosaccharides and polysaccharides. i) Starch ii) fructose iii) sucrose iv) lactose iv) maltose

i) Starch - Polysaccharides

ii) fructose - Monosaccharide

iii) sucrose - Disaccharide

iv) lactose - Disaccharide

iv) maltose - Disaccharide

12. How are vitamins classified

i) Water soluble vitamins. Eg: Vitamin C, B complexes

ii) Fat soluble vitamins. Eg: Vitamin A, D, E, K.

13. What are harmones? Give examples

Hormone is an organic substance (e.g. a peptide or a steroid) that is secreted by one tissue into the blood stream and induces a physiological response in other tissues. It is an intercellular signalling molecule.

Example: Insulin, estrogen

14. Write the structure of all possible dipeptides which can be obtained form glycine and alanine

The possible dipeptides obtained from glycine and alanine

15. Define enzymes

The biochemical reactions that occur in our living cells are catalysed by special proteins called enzymes. They are highly specific in nature.

16. Write the structure of α-D (+) glucophyranose

17. What are different types of RNA which are found in cell ?

i. Ribosomal RNA (rRNA)

ii. Messenger RNA (mRNA)

iii. Transfer RNA (tRNA)

18. Write a note on formation of α-helix .

The amino acids are arranged in a right handed helical (spiral) structure

They are stabilised by the hydrogen bond between the carbonyl oxygen of one amino acid (nth residue) with amino hydrogen of the fifth residue (n+4th residue).

The side chains of the residues project outside of the helix.

Each turn of an α-helix contains about 3.6 residues and is about 5.4 Ǻ long.

The amino acid proline produces a bend in the helical structure and often called as a helix breaker due to its rigid cyclic structure.


19. What are the functions of lipids in living organism.

1. Lipids are the integral component of cell membrane.

2. Triglycerides is an energy reserve.

3. They act as protective coating in aquatic organisms.

4. Lipids of connective tissue give protection to internal organs.

5. Lipids help in the absorption and transport, of fat soluble vitamins.

6. They are essential for activation of enzymes such as lipases.

7. Lipids act as emulsifier in fat metabolism. 

20. Is the following sugar, D – sugar or L – sugar?



Because the H and OH on C4 carbon are in the same configuration as the H and OH on C2 carbon in L-glyceraldehyde.

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