PROTEIN STRUCTURE AND BIOLOGICALLY IMPORTANT PEPTIDES

PROTEIN STRUCTUTRE AND PREVIOUS ALL INDIA , AIIMS , PGI CHANDIGARH , NEET QUESTIONS

1. Structure of Proteins PRIMARY STRCUTURE

2. Peptide bond Properties of proteins Biologically important peptides

3. Peptide bond covalent rigid and planar with partial double bond in character . trans configuration. Both -C=O and –NH groups of peptide bonds are polar involved in hydrogen bond formation . Peptides containing > 10 amino acids - polypeptides .

4. G lutathione

5. WHAT IS THE AVERAGE NUMBER OF HIGH ENERGY BONDS REQUIRED FOR THE SYNTHESIS OF ONE PEPTIDE BOND A 1 B 2 C 3 D 4

6. PROPERTIES OF PROTEINS

7. OVAL ALBUMIN GLOBULAR INSULIN SHAPE

8. ratio Lys + Arg /( g lu + Asp) ratio > 1 B asic proteins. Acidic proteins, ratio < 1 . Acidic and basic proteins :

9. Precipitation of proteins

10. . Milk forms a solid curd on standing ·        bacteria in milk grows ·        forms lactic acid pl 4.6 For casein ·         becomes isoelectric ·        coagulates into a solid curd PRECIPITATION AT pI

11. Higher is the protein molecular weight, the lower is the salt required for precipitation globulins are precipitated by half saturation with ammonium sulfate albumin is precipitated by full saturation. Salting out procedure is Used for separating serum albumins from globulin

12. Biuret Test

13. Chemical Reaction in the Biuret test

14. NINHYDRIN REACTION GIVES A PURPLE COLOUR AND EVOLVES CO2 A WITH PEPIDE BONDS B WITH HISTAMINE C WITH ASPARAGINE D WITH SEROTONIN

15. INTACT PEPTIDE BOND IS NECESSARY FOR WHICH TEST A UV DIFFRACTION B NINHYDRIN C DIAZO REACTION D ALL

16. MILLONS TEST IS POSITIVE IN A MAPLE SYRUP URINE DISEASE B HARTNUP DISEASE C WILSONS DISEASE D TYROSINOSIS

17. MILLONS TEST IS USED IN THE DETECTION OF A PHENYL ALANINE B CYSTINE C TYROSINE D TRYPTOPHAN

18. CYSTINURIA IS DIAGNOSED BY WHICH TEST A FOLINS COICALTEAUS TEST B MILLONS TEST C XANTHOPROTEIC TEST D CYANIDE NITROPROSSIDE TEST

19. HOPKINS COLE REACTION DETECTS AMINO ACID CONTAINING INDOLE RING A ARGININE B TRYPTOPHAN C TYROSINE D HISTIDINE

20. BIOLOGICALLY IMPORTANT PEPTIDES

21. Meister cycle in intestine

22. Glutathione is involved in detoxication s organophosphates,nitro compounds are converted to mercapturic acids

23. WHICH OF THE FOLLOWING IS TRUE ABOUT GLUTATHIONE A CONTAINS SULFHYDRYL GROUPS B FORMS MET Hb FROM Hb C TRANSPORT AMINO ACID ACROSS CELL MEMBRANE D PART OF ENZYMES

24. REGARDING GLUTATHIONE WHICH OF THE FOLLOWING IS TRUE A IT HELPS THE ABSORPTION OF AMINO ACIDS B IT INACTIVATES SOME ENZYMES C IT HELPS IN MEMBRANE TRANSPORT D IT HELPS IN CONJUGATION REACTIONS

25. IN GLUTATHIONE WHICH AMINO ACID IS REDUCING A GLUTAMIC ACID B GLYCINE C CYSTEINE D ALANINE

26. GASTRIN

27. SECRETIN

28. Vassopressin

29. Vasopressin Vasopressin is also called ADH (antidiuretic hormone) Vasopressin increases blood pressure and inhibits diuresis. It constricts blood vessels rising the blood pressure and affecting water and electrolyte balance

30. Gramicidin S Gramicidin S is an antibiotic for topical use and effective for gram-positive bacterial infection.

31. TRH

32. Denaturation LOST  : quaternary , tertiary , secondary structure INTACT : PEPTIDE BOND DISORGANISATION OF NATIVE PROTEIN STRUCTURE PHYSICAL , CHEMICAL , BIOLOGICAL PROPERTIES CHANGED SOLUBILITY ↓ VISCOSITY ↑ ACTIVITY ↓ ,

33. Denaturationis associated with increase in ionizable and sulfhydryl groups of protein . due to loss of hydrogen and disulfide bonds

34. Denaturation Usually irreversible cooking eggs Denatured protein is easily digested . increased exposure of peptide bonds to enzyme Cooking , HCL causes protein denaturation Protein is easily digested by PEPSIN

35. haemoglobin salicylate

36. Flocculation : protein precipitation at isoelectric pH precipitate is referred to as flocculum . Casein (milk protein) can be easily precipitated when adjusted to isoelectric pH 4.6 by dilute acetic acid . Flocculation is reversible. On application of heat , flocculum can be converted into an Irreversible mass, coagulum .

37. Coagulation : The term 'coagulum' refers to semi-solid viscous precipitate of protein . lrreversible denaturation lowest temperature at isoelectric pH. Albumins and globulins are coagulable proteins. Heat coagulation test used to detect albumin in urine.

38. Agents of denaturation Physical agents : Heat, violent shaking, X- ravs , UV rays Chemical agents : Acids, alkalies , organic solvents (ether, alcohol), salts of heavy metals ( Pb , Hg), urea, salicylate.

39. All are true about denaturation except A all bonds are disrupted except peptide bond B all structures are disrupted except primary structure C function is preserved D on removal of denaturing force renaturation normally does not occur

40. HEAT TEST FOR PROTEIN Take 2/3 of test tube full of urine sample hold the test tube from the bottom and heat the top portion of tube. add a drop of 1%acetic acid .do not mix Normally when urine ph is acidic White precipitate in the heated portion indicating the presence of albumin

41. if urinary ph is alkaline proteins may not be precipitated owing to formation of meataproteins which are not precipitated on heating phosphates will be precipitated and give a false positive test on acidification with 1% acetic acid drop by drop phosphate will disappear and precipitate of albumin will appear on acidification

42. PROTEIN ESTIMATION TEST IS CONFUSED WITH A PHOSPHATE B NITRATE C SULPHATE D BILE SALTS