Nucleic Acids, Amino Acids, Proteins, and Enzymes — DU B.Sc (hons) Chemistry Previous Year Question Papers

ACIDS, PROTEINS AND ENZYMES DSC 14 2. All questions have equal marks 1. (i) Repeated Edman degradations of the hexapeptide Ala-Phe-Ser-Val-Trp-Gly yielded an amino acid derivative 'A' and a peptide 'B' after the first cycle and an amino acid derivative 'C' along with a peptide 'D' after the second cycle. Write all the reactions involved in these two cycles of Edman degradation. Label the structures A, B, (ii) What are different types of RNA? Discuss their biological functions. (iii) List the six main groups of enzymes according to the Enzyme Commission. What functions do they perform? (5,5,5) 2. (i) What are the products formed when the hydrolysis of the following peptide is catalyzed by the enzyme a) Trypsin and b) Chymotrypsin (ii) What is the difference between a competitive and noncompetitive enzyme inhibition? (iii) What is DCC and what role does it play in peptide synthesis? Discuss with an example. (iv) What are essential amino acids? Name any two giving their structure. (4,4,4,3) 3. (I) Explain the mechanism of action of the enzyme (ii) Write the names and draw the structures of nitrogenous bases present in DNA. What is the name of the sugar moiety present in DNA? (111) Briefly describe the factors affecting enzyme activity. (5,5,5) 4. (i) How does carboxypeptidase enzyme help with peptide chain C-terminal residue analysis? (ii) How would you synthesize the tripeptide Ser- Phe-Ala using solid phase peptide synthesis? (iii) Explain the principle of electrophoresis. How do we separate a mixture of amino acids using electrophoresis? Discuss with example. 5. (i) Differentiate between : (a) a-Helix and B-pleated sheets (b) Lock and Key Model and Induced Fit Model of Enzyme Action (ii) Write the names and draw the structures of all the dipeptides formed using the two amino acids Phe and Gly. (iii) Discuss a method to synthesize (D, L)-Tyrosine (iv) Why is DNA replication semiconservative in nature? (4,4,4,3) 6. Write short notes on the following: (Any 3) (i) Translation and Transcription (ii) Denaturation of proteins (111) Importance of Ninhydrin reagent (iv) Genetic Code (5,5,5)