The following questions are case-based questions. Each question has an internal choice and carries 4 (1+1+2) marks each. Read the passage carefully and answer the questions that follow.
Proteins are the most abundant biomolecules of the living system. The chief sources of proteins are milk, cheese, pulses, fish, meat, peanuts, etc. They are found in every part of the body and form a fundamental basis of the structure and functions of life. These are also required for the growth and maintenance of the body. The word protein is derived from the Greek word, ‘proteios’ meaning ‘primary’ or of ‘prime importance’. Chemically, proteins are the polymers in which the monomeric units are the α-amino acids. Amino acids contain an amino (-NH₂) and carboxylic (-COOH) functional groups. Depending upon the relative position of the amino group with respect to the carboxylic group, the amino acids can be classified as α, β, and γ-amino acids. Amino acids which are synthesised by the body are called non-essential amino acids. On the other hand, those amino acids which cannot be synthesized in the human body and are supplied in the form of diet (because they are required for proper health and growth) are called essential amino acids.
(i) Amino acids show amphoteric behavior. Why?
(ii) The name of linkage joining two amino acids.
(iii) What are polypeptides?
a) 10 < α-amino acids joined together
b) amino acids joined together
c) 20 < β-amino acids joined together
d) None of the above
(iv) What type of bonding helps in stabilizing the α-helix structure of proteins?
OR
(a) What are essential and non-essential amino acids? Give two examples of each.
(b) How are nucleosides different from nucleotides?

Question

The following questions are case-based questions. Each question has an internal choice and carries 4 (1+1+2) marks each. Read the passage carefully and answer the questions that follow.
Proteins are the most abundant biomolecules of the living system. The chief sources of proteins are milk, cheese, pulses, fish, meat, peanuts, etc. They are found in every part of the body and form a fundamental basis of the structure and functions of life. These are also required for the growth and maintenance of the body. The word protein is derived from the Greek word, ‘proteios’ meaning ‘primary’ or of ‘prime importance’. Chemically, proteins are the polymers in which the monomeric units are the α-amino acids. Amino acids contain an amino (-NH₂) and carboxylic (-COOH) functional groups. Depending upon the relative position of the amino group with respect to the carboxylic group, the amino acids can be classified as α, β, and γ-amino acids. Amino acids which are synthesised by the body are called non-essential amino acids. On the other hand, those amino acids which cannot be synthesized in the human body and are supplied in the form of diet (because they are required for proper health and growth) are called essential amino acids.
(i) Amino acids show amphoteric behavior. Why?
(ii) The name of linkage joining two amino acids.
(iii) What are polypeptides?
a) 10 < α-amino acids joined together
b) amino acids joined together
c) 20 < β-amino acids joined together
d) None of the above
(iv) What type of bonding helps in stabilizing the α-helix structure of proteins?
OR
(a) What are essential and non-essential amino acids? Give two examples of each.
(b) How are nucleosides different from nucleotides?

Infinity Learn · Accepted Answer

(i) Amino acids have amino (−NH2) group, basic in nature and accepts a proton and COOH group loses a proton forming a dipolar ion, called the Zwitter ion. In this form, amino acids behave both as acids and bases so they are amphoteric in nature.

(ii) A peptide bond (amide bond) is a covalent chemical bond linking two consecutive amino acid monomers.

(iii) 10 < α-amino acids joined together

(iv) Hydrogen bonds are stabilizing an alpha-helix.

OR

(A) Non-essential amino acids : The amino acids which can be synthesised in the body, are known as non-essential amino acids. Example : Glycine, Alanine etc. Essential amino acids : The amino acids which cannot be synthesised in the body and must be obtained through diet are known as essential amino acids. Example : Valine, Leucine etc.

(B) Nucleoside : A nucleoside contains only two basic components of nucleic acids i.e. a pentose sugar and a nitrogenous base. During their formation 1-position of the pyrimidine or 9-position of the purine moitey is linked to C1 of the sugar (ribose or deoxyribose) by a β-linkage.

Question Image
Nucleotides : A nucleotide contains all the three basic components of nucleic acids, i.e. a phosphoric acid group, a pentose sugar and a nitrogenous base. These are formed by esterification of C5‘ – OH of the sugar of the nucleoside with phosphoric acid.

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