Assertion: Glycine is not optically optically active. Reason: There is no asymmetrical carbon in glycine to make it chiral. A. Assertion and reason both are correct statements and reason is correct explanation for assertion. B. Assertion and reason both are correct statements but reason is not correct explanation for assertion. C. Assertion is correct statement but reason is wrong statement. D. Assertion is wrong statement but reason is correct statement.

Read the passage given below and answer the following questions: When a protein in its native form, is subjected to physical changes like change in temperature or chemical changes like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of protein. The denaturation causes change in secondary ann tertiary structures but primary structures remain intact. Examples of denaturation of protein are coagulation of egg white on boiling, curdling of milk, formation of cheese when an acid is added to milk. Choose the most appropriate answer: i) Mark the wrong statement about denaturation of proteins. a) The primary structure of the protein does not change. b) Globular proteins are converted into fibrous proteins. c) Fibrous proteins are converted into globular proteins. d) The biological activity of the protein is destroyed. ii) Which structure{s) of proteins remains(s) intact during denaturation process? (a) Both secondary and tertiary structures (b) Primary structure only (c) Secondary structure only (d) Tertiary structure only iii) a-helix a n d β - pleated structures of proteins are classified as (a) primary structure (b) secondary structure (c) tertiary structure (d) quaternary structure. (iv) Secondary structure of protein refers to a) mainly denatured proteins and structure of prosthetic groups. b) three-dimensional structure, especially the bend between. amino acid residues that are distant from each other in the polypeptide chain. c) linear sequence of amino acid residues in the polypeptide chain. d) regular folding patterns of continuous portions of the polypeptide chain.

The sequence of bases along the DNA and RNA chain establishes its primary structure which controls the specific properties of the nucleic acid. An RNA molecule is usually a single chain of ribose-containing nucleotide. On the basis of X-ray analysis of DNA, J.D., Watson and F.H.C. CYST (shared noble prize in 1962) proposed a three dimensional secondary structure for DNA. DNA molecule is a long and highly complex, spirally twisted, double helix, ladder like structure. The two polynucleotide chains or strands are linked up by hydrogen bonding between the nitrogenous base molecules of their nucleotide monomers. Adenine (purine) always links with thymine (pyrimidine) with the help of two hydrogen bonds and guanine (purine) with cytosine (pyrimidine) with the help of three hydrogen bonds. Hence, the two strands extend in opposite directions, i.e., are antiparallel and complimentary. In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. a) Assertion and reason both are correct statements and reason is correct explanation for assertion. b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. c) Assertion is correct statement but reason is wrong statement d) Assertion is wrong statement but reason is correct statement. i) Assertion - DNA molecules and RNA molecules are found in the nucleus of a cell. Reason : There are two types of nitrogenous bases, purines and pyrimidines. Adenine (A) and guanine (G)are substituted purines; cytokine (C), thymine (T) arid uracil (U) are substituted pyrimidines. ii) Assertion .- In both DNA and RNA, heterocyclic base and phosphate ester linkages are at C- 1’ and C-5’respectively of the sugar molecule. Reason : Nucleotides and nucleosides mainly differ from each other in presence of phosphate units. iii)Assertion .- The backbone of RNA molecule is a linear chain consisting of an alternating units of heterocylic base, D-ribose and a phosphate. Reason : The segment of RNA which acts as the instruction manual for the synthesis of protein is ribose. iv) Assertion.- In DNA, the complementary bases are, adenine and guanine; thymine and cytosine. Reason : The phenomenon of mutation is chemical change in DNA molecule.

Proteins are high molecular mass complex biomolecules of amino acid The important proteins required for our body are enzymes, hormones, antibodies, transport proteins, structural proteins, contractile proteins etc. Except for glycine, all o-amino acids have chiral carbon atom and most of them have L-configuration. The amino acids exists as dipolar ion called zwitter ion, in which a proton goes from the carboxyl group to the amino group. A large number of-amino acids are joined by peptide bonds forming polypeptides. The peptides having very large molecular mass (more than 10,000) are called proteins. The structure of proteins is described as primary structure giving sequence of linking of amino acids; secondary structure giving manner in which polypeptide chains are arranged and folded; tertiary structure giving folding, coiling or bonding polypeptide chains producing three dimensional structures and quaternary structure giving arrangement of sub- units in an aggregate protein molecule. In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. a) Assertion and reason both are correct statements and reason is correct explanation for assertion. b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. c) Assertion is correct statement but reason is wrong statement. d) Assertion is wrong statement but reason is correct statement. i) Assertion .- All amino acids are optimally active. Reason : Amino acids contain asymmetric carbon atoms. ii) Assertion .- In o-helix structure, intramolecular H-bonding takes place whereas in β-pleated structure,intermolecular H-bonding takes place. Reason : An egg contains a soluble globular protein called albumin which is present in the white part. iii) Assertion .- Secondary structure of protein refers to regular folding patterns of continuous portions of the polypeptide chain Reason : Out of 20 amino acids, only 12 amino acids can be synthesized by human body. iv) Assertion .- The. helical structure of protein is stabilized by intramolecular hydrogen bond between —NH and carbonyl oxygen. Reason : Sanger’s reagent is used for the identification of N-terminal amino acid of peptide chain.