Anna University Biochemistry Model Test Paper

Anna University Biochemistry Model Test Paper

III Semester

BIOCHEMISTRY 

Max. Marks: 100                                                                                           Time: 3 hours

 

PART – A (10 x 2 = 20 Marks)

Answer ALL the Questions

 

1. What is the cost in ATP equivalents of transforming glucose to Pyruvate via glycolysis and back again to glucose via gluconeogenesis?

2. Name two uncouplers of oxidative phosphorelation and what is respiratory quotient?

3. What is transamination? Give an example?

4. What is the role of biotin?

5. Give the structures of four high-energy phosphate compounds?

6. Mention at least three ways by which metabolic pathways are regulated?

7. Give the repeating unit of a homopolysaccharide and a heteropolysaccharide?

8. Give the function of carnitine?

9. What is a mirror-repeat and an inverted repeat?

10. Name two second messengers?

 

PART – B (5 x 16 = 80 Marks)

Question No. 11 is compulsory

 

11. (a) Describe the co-ordinate control of gluconeogenesis and glycolysis? ( 6 marks)

(b) Give the overall equation for both pathways? (2 marks)

(c) Give the irreversible reactions in both pathways? (3 marks)

(d) Mention the ATP-generating and ATP-consuming reactions? (4 marks)

(e) Give the substrate level phosphorylation reaction in glycolysis? (1 mark)

 

12. (1) What is the role of citric acid cycle in anabolism? (2 marks)

(2) Give the reactions of the glyoxylate shunt? (3 marks)

(3) How can you get net synthesis of a – ketoglutarate from pyruvate? (4 mark)

(4) Give the reaction catalyzed by the pyruvate dehydrogenase complex. List the enzymes and cofactors? (3 marks)

(5) Give 2 reactions of oxidative decarboxylation in the Krebs cycle? (2 marks)

(6) List 2 anaplerotic reactions? (2 marks)

OR

Describe the structure of DNA.

 

13. Describe the secondary structure of proteins?

OR

Write a note on nitrogen balance and how is excess nitrogen excreted in ureotelic animals?

14. Complete amino acid hydrolysis of the peptide followed by amino acid analysis yielded equimolar amounts of L, O, F, P, V. (O – orinthine). The molecular weight of the peptide was established as about 1200. The peptide failed to undergo hydrolysis when treated with carboxypeptidase. (Does not cleave if C-terminal residue is P or does not contain a free carboxyl. Complete hydrolysis by 6N HCl at 110oC followed by amino acid analysis indicated the presence of G, L, F and Y in 2:1:1:1 molar ratio, treatment with FDNB yielded 2,4-DNP-Y. No free Y was found. Complete digestion of the peptide with pepsin followed by chromatography yielded a dipeptide containing F & L, plus a tripeptide containing Y & G in 1:2 ratios. Determine the sequence and explain how your results are consistent with each piece of information.

OR

Describe Fatty Acid biosynthesis (8 marks)

Contrast it with b – oxidation (4 marks)

Write the complete equation for both  (2 marks)

Give the total ATP yield from the complete oxidation of stearic acid? (2 marks)

15. Treatment of an intact peptide with 1- Fluoro 2,4-dixitiobenzene followed by complete hydrolysis & chromatography yielded only free amino acids and the following derivative

NO2                                                        H

|

O2N                                    NH – CH2 – CH2 – CH2 – C – COO

|

NH3

 

(HINT: 2, 4-DNP amino acid involves the amino group of the side chain rather than the a – amino group.)

 

Partial hydrolysis of the peptide followed by chromatographic separation and sequence analysis yielded the following di-and tri-peptides.

 

L-F,  F-P,  O-L,  V-O,  V-O-L,  F-P-V,   P-V-O.

 

Given the above information, deduce the amino acid sequence of the peptide antibiotic. Show your reasoning when you have arrived at the structure. Demonstrate it is consistent with the above findings.

OR

(1)  Give the structure of the hydrolysis products of RNA (partial & Complete) (4 marks)

(2) Describe the structure of t-RNA (2 marks)

(3) What is wobble hypothesis (1 mark)

(4) What are the features of the genetic code (2 marks)

(5) How would you differentiate DNA from RNA? (2 marks)

(6)  How is DNA replicated? Give the experiment, which proved the above mechanism? (3 marks)

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