Biomolecules Class 12 Chemistry Important Questions

Please refer to Biomolecules Class 12 Chemistry Important Questions with solutions provided below. These questions and answers have been provided for Class 12 Chemistry based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these problem solutions as it will help them to gain more marks in examinations. We have provided Important Questions for Class 12 Chemistry for all chapters in your book. These Board exam questions have been designed by expert teachers of Standard 12.

Class 12 Chemistry Important Questions Biomolecules

Very Short Answer Questions

Question. Define the following term :
Invert sugar 
Answer. An equimolar mixture of glucose and fructose, obtained by hydrolysis of sucrose in presence of an acid or the enzyme invertase is called invert sugar

Question. State two functions of carbohydrates.
Answer. (i) Carbohydrates act as storage molecules as starch in plants and glycogen in animals.
(ii) They act as constituent of cell membrane.

Question. Explain what is meant by the following :
pyranose structure of glucose?
Answer. The six membered cyclic structure of glucose is called pyranose structure (a-or β –), in analogy with heterocyclic compound pyran.

Question. Amino acids show amphoteric behaviour. Why?
Answer. As amino acids have both acidic (carboxy group) and basic groups (amino group) in the same molecule, they react with both acids and bases. Hence, they show amphoteric behaviour.

Question. What is the difference between acidic amino acids and basic amino acids?
Answer. Acidic amino acids are those which contain more number of carboxyl groups as compared to amino groups whereas basic amino acids are those which contains more number of amino groups than carboxyl groups.

Question. What type of linkage is responsible for the formation of proteins?
Answer. Peptide linkage

Question. Define the following term :
Essential amino acids 
Answer. Essential amino acids : Amino acids which cannot be synthesized in the body and must be obtained through diet are known as essential amino acids. e.g., valine, leucine, etc.

Question. Define the following term :
Denaturation of proteins
Answer. Denaturation : The loss of biological activity of a protein by changing the pH, temperature or by adding some salt due to disruption of the native structure of protein is called denaturation. During denaturation secondary and tertiary structure of protein is destroyed but primary structure remains intact.

Question. Define the following term :
Amino acids 
Answer. Organic compounds containing both amino ( — NH₂) and carboxy ( COOH) functional groups are called amino acids.

Question. Define a ‘Peptide linkage’.
Answer. Proteins are the polymers of a-amino acids linked by amide formation between carboxyl and amino group. This is called peptide linkage or peptide bond e.g.,

Question. Where does the water present in the egg go after boiling the egg? 
Answer. An egg contains a soluble globular protein called allumin which is present in the white part. On boiling, denaturation (loss of biological activity) of this protein takes place which results in the formation of insoluble fibrous proteins. The water molecules are utilized in this process.

Question. Explain the following term :
Polypeptides
Answer. Polypeptides are the macromolecules formed by combination of 10 or more amino acids.

Question. Define the following term :
Enzymes.
Answer. Enzymes : Most of the chemical reactions which occur in living systems process at very slow rates under mild condition of temperature and pH. These reactions are catalysed by a group of biomolecules called enzymes.

Question. What is meant by biocatalysts?
Answer. Substances which catalyse chemical reactions taking place in living organisms are called biocatalysts. e.g., enzymes

Question. Deficiency of which vitamin causes rickets?
Answer. Vitamin D

Question. Deficiency of which vitamin causes scurvy?
Answer. Vitamin C

Question. Name the Deficiency diseases resulting from lack of Vitamins A and E in the diet.
Answer. Vitamin – A : Night blindness
Vitamin E : Muscular weakness.

Question. Name one of the water soluble vitamin which is powerful antioxidant. Give its one natural source. 
Answer. Vitamin C is water soluble and powerful antioxidant. Natural source of vitamin C is amla.

Question. How are hormones and vitamins different in respect of their source and functions?
Answer.

Question. Name the only vitamin which can be synthesized in our body. Name the disease caused due to the Deficiency of this vitamin.
Answer. Vitamin D
Disease caused due to deficiency of Vitamin D is rickets.

Question. The deficiency of which vitamin causes the disease, ‘pernicious anaemia’?
Answer. Vitamin B₁₂

Question. Name two water soluble vitamins, their sources and diseases caused due to their deficiency in diet.
Answer. Examples of water soluble vitamins :
Vitamin B and vitamin C.

Question. What is difference between a nucleoside and nucleotide?
Answer. Nucleoside contains pentose sugar, and base whereas nucleotide contains pentose sugar, base as well as phosphate group.
Nucleoside = Base + Sugar
Nucleotide = Base + Sugar + Phosphate.

Question. What type of linkage is present in nucleic acids?
Answer. Ester linkage

Question. Name of the base that is found in nucleotide of RNA only.
Answer. Uracil

Question. Mention one important function of nucleic acids in our body.
Answer. DNA is reserve of genetic information and responsible for heredity transmission.

Question. Name of the purines present in DNA.
Answer. Adenine and guanine

Short Answer Questions

Question. Enumerate the reactions of glucose which cannot be explained by its open chain structures.
Answer. The following reactions of D-glucose cannot be explained on the basis of its open chain structure :
(i) D-Glucose does not react with sodium bisulphite (NaHSO₃).
(ii) It does not give 2, 4-DNP test and Schiff ’s test.
(iii) The pentaacetate of D-glucose does not react with hydroxylamine.
(iv) D-Glucose shows the phenomenon of mutarotation, i.e., when its aqueous solution is kept for sometime its optical activity changes.
(v) On reaction with 1 mole of methanol, it yield two monomethyl derivatives which are known as methyl a-D-glucoside and methyl-b-Dglucoside.

Question. Mention the type of linkage responsible for the formation of the following :
(i) Primary structure of proteins
(ii) Cross-linkage of polypeptide chains
(iii) a-helix formation
(iv) b-sheet structure
Answer. 

(i) Primary structure of protein	Peptide bond (linkage)
(ii) Cross linkage of	Hydrogen bonds,
polypeptide chain	disulphide linkage, electrostatic force of attraction
(iii) a-helix formation	Hydrogen bond
(iv) b-sheet structure	Intermolecular hydrogen bonds

Question. Name the four bases present in DNA. Which one of these is not present in RNA?
Answer. DNA contains four bases viz adenine (A) guanine (G), cytosine (C), and thymine (T). RNA also contains four bases but thymine is not present in RNA.

Question. Describe what you understand by primary structure and secondary structure of proteins?
Answer. Primary structure : The specic sequence in which the various amino acids present in a protein are linked to one another is called its primary structure. Any change in the primary structure creates a different protein.
Secondary structure : The conformation of the polypeptide chain is known as secondary structure.
The two types of secondary structure are a-helix and β-pleated sheet structure.
In a-helix structure, the polypeptide chain forms all the possible hydrogen bonds by twisting into a right handed screw (helix) with the NH groups of each amino acid residue hydrogen bonded to the

group of an adjacent turn of the helix. In b-pleated sheet structure, all peptide chains are stretched out to nearly maximum extension and then laid side by side which are held together by intermolecular hydrogen bonds.

Question. Name two fat soluble vitamins, their sources and the diseases caused due to their deficiency in diet.
Answer. Examples of fat soluble vitamins are vitamin A and D.

Question. When RNA is hydrolysed, there is no relationship among the quantities of different bases formed. What does this fact suggest about the structure of RNA?
Answer. When a RNA molecule is hydrolysed then there is no relationship between the quantities of four bases viz. adenine (A), guanine (G), cytosine (C), and uracil (U). This fact suggests that RNA has single stranded structure.

Long Answer Questions

Question. What are the different types of RNA found in cells of organisms? State the functions of each type.
Answer. RNA are of three types :
(i) Messenger RNA (m-RNA) : Function as messenger carrying the information in a gene to the protein synthesizing machinery.
Transfer RNA (t-RNA) : They transfer the amino acids from cytoplasm to the protein synthesizing machinery.
(ii) Ribosomal RNA (rRNA) : They associates with a set of proteins to form ribosomes.
These complex structures, which physically move among an mRNA molecule, catalyze the assembly of amino acids into protein chains. They also bind t-RNAs and various molecules necessary for protein synthesis.