IGNOU BCHET-149 - Molecules of Life

Part-A 1. a) Differentiate between a prokaryotic and a eukaryotic cell in terms of their structure. b) How are lysosomes formed in the cells. Describe their role within the cell. 2. a) What do capital letters D and L signify in the context stereochemistry of monosaccharides? Explain with the help of an example. b) Write a reaction that is used in distinguishing an aldose from a ketose. How does an aldose react with phenylhydrazine? Give the reaction involved and explain. 3. a) What is milk sugar? How is it formed? Explain giving the reaction. b) How are amino acids represented? Explain with the help of an example. Describe in brief the configuration of amino acids. 4. a) Describe the behaviour of amino acids in acidic and basic medium. What is the significance of their Zwitterionic Nature? b) How is peptide bond formed? Explain the stereochemistry of a peptide bond. 5. a) Describe in brief the Merrifield solid phase synthesis of peptides. b) Describe the covalent interactions involved in protein folding. Part-B 6. a) Explain the physiological aspect of specificity of enzyme action that distinguishes it from the non-enzyme part in a catalyst. b) What is Michaelis-Menton equation? Describe its significance in affecting the rate of an enzymatic reaction. 7. a) Describe the structural and functional basis of classification of lipids. b) What are phospholipids? Describe in brief the different classes of phospholipids. 8. a) Differentiate between nucleosides and nucleotides and illustrate your answer. b) Name and describe the experiment which proved that ‘DNA is the material that communicates the genetic information’. 9. a) What are coupling reactions? Explain their significance in biochemical reactions. b) Write the mechanism of conversion of G-3-P into pyruvate. 10. a) What is substrate chanelling in Kreb’s cycle? Explain. b) Compare the degradation and the biosynthesis of fatty acids.

PART-A 1. (a) Describe the method for fractionation of subcellular organelles. (b) What is the role of Golgi bodies in protein processing? Illustrate with the help of a diagram.  2. (a) Name the storage polysaccharides present in animals and plants. Indicate the structural differences between these. (b) i) What are lipoproteins? Name the major groups of lipoproteins. (ii) What is the significance of phospholipids in the membrane structure and function.  3. (a) Why are the amino acids called -amino acids? The amino acids tyrosine and tryptophan have nonpolar side chains; still these are placed in the uncharged polar group, why? Write the advantages of polar side chains in the amino acids. (b) Describe the stereochemistry of the peptide bond and explain how this is significant in restricting the number of conformations of a polypeptide chain. 4. (a) How does the pH affect the activity of enzymes in the biological systems? Illustrate your answer. (b) What is the significance of vitamins and minerals in the living system? Write one biochemical reaction in which the coenzyme of cyanocobalmin is associated and explain the mechanism of the reaction. 5. (a) When is a reaction called spontaneous? Differentiate between ΔG and ΔG o and describe their significance in predicting the direction of a biochemical reaction. (b) What is meant by the turnover of ATP? How is oxidative phosphorylation related to it? Write the steps involved in the phosphorylation process. PART-A 6. a) Differentiate between anabolism and catabolism. Write the mechanism of the reaction of conversion of glyceraldehyde-3-phosphate to pyruvate. b) Describe the process of biosynthesis of fatty acids catalysed by fatty acid synthase. 7. a) How is feedback regulation different from allosteric regulation? Name the most important regulatory enzyme and its allosteric effector in the glycolytic pathway. Also write the reaction catalysed by this enzyme. (b) Define photophosphorylation. Differentiate between substrate level and oxidative phosphorylation. 8. a) Describe the structure and role of ribosome in protein synthesis. (b) What are the advantages of using immobilized enzymes? How is the production of enzymes from microorganisms carried out?  9. a) Describe the role of DNA polymerase in DNA replication. (b) Describe the process of unwinding of the double helix during DNA replication. 10. (a) Name two carbohydrates that are metabolised by glycolysis. Write the reactions and enzymes involved in their entry into the glycolytic pathway. (b) Describe the pathways involved in the removal of amino group from amino acids.