Monday, October 22, 2012

Chemistry of Proteins


1-Give an example of reversible denaturation

(Denaturation of Ribonuclease by urea)

 2. Give example of a circular peptide.

(Gramicidin S)

 3-What is the difference between Salting in and Salting out?

(Salting in is addition of a pinch of salt to increase the solubility of a protein, while salting out is addition of excess of salt to precipitate it out)

4. Name the proteins containing alpha helical structure predominantly.

(Hemoglobin, Myoglobin etc)

5. Name the super secondary structures

(Greek key, beta meanders, Beta alpha beta)

6. Name the respiratory proteins

(Hemoglobin, Myoglobin, cytochromes)

 7. What is the class of Zein protein?

(Poor protein- it lacks Tryptophan and Lysine)

 8. Name the contractile proteins

( Actin, Myosin, flageller proteins)

 9-What are the features of isoelectric pH?

(Decrease in solubility, electric charge, Electrophoretic migration, loss of biological activity)

 10-What is the basis of protein precipitation by organic solvents?

(Decrease in dielectic constant of the medium)

11-What is the difference between flocculum and coagulum?

(Flocculum is a reversible state of denaturation while coagulum is a an irreversible state of denaturation)

12-What are the forces that stabilize the alpha helical structure?

(Hydrogen and Vander waals forces mainly)

13-What is the basis of cauterization by silver nitrate during surgery to control bleeding?

(Silver nitrate is a heavy metal salt and by causing precipitation of proteins seals the oozing points of the blood vessels)

14-What is meant by a domain?

(Domain is a term used to denote a compact globular functional unit of a protein)

15-Why is Glutathione called a pseudo peptide?

(In glutathione instead of alpha carboxyl group, the gamma carboxyl participates in the peptide bond formation)

16-Covalent forces stabilize the tertiary structure in a protein- True or false?

(False- the non covalent forces stabilize the tertiary structure in a protein)

17- Which tests should be carried out for the detection of Tryptophan in a given solution?

(Xanthoproteic and Hopkins Cole test)

18- Which amino acids contribute towards ionic interactions?

(Positively charged amino acids like Arginine , Lysine and negatively charged amino acids like Aspartic acid and Glutamic acid)

19- Which protein is precipitated by full saturation with Ammonium sulphate?

(Albumin)

20- What is the relationship of amount of salt required and the molecular weight of a protein?

(More the molecular weight and lesser is the amount of salt required by the protein and vice versa)

21-What are the functions of proteins?

(Nutritive, buffering, defense, viscosity, osmotic pressure, enzymes, hormones etc)

22-Name mono amino dicarboxylic acids

 (Aspartic and Glutamic acid)

 23-Name heterocyclic amino acids

 (Tryptophan and Histidine)

 24-Name the 21st and 22 nd amino acid

 (Seleno cysteine and Pyrrolysine)

 25-Which amino acids are involved in forming N- Glycosidic linkages?

 (Asparagine and Glutamine)

26-Name the semi essential amino acid

(Arginine and Histidine)

27-Which amino acid acts as the precursor of vitamin Niacin?

 (Tryptophan)

28-Name the amino acids with a non polar side chain

(Alanine, Valine, Leucine Isoleucine, Methionine, Phenyl Alanine)

29-Which protein structure determines the relationship of amino acids which are 3-4 residues apart ?

 (Tertiary structure)

30-Which test will be negative for a protein lacking tryptophan ?

 (Hopkins cole test)

 31-Name the essential amino acids

( Valine, Leucine, Isoleucine, lysine, Phenylalanine, Methionine and Threonine)

 32-Which amino acid is optically inactive ?

(Glycine)

 33-Which amino acid is abundantly present in prolamines ?

(Proline)

 34-Which protein is mostly found attached to DNA?

(Histone)

 35-Name the amino acids which are both glucogenic as well as ketogenic

(Isoleucine. Phenyl Alanine, Tyrosine and Tryptophan)

35-Name a specific test for the detection of alpha amino acids

(Ninhydrin test)

 36-Name a  specific test for the detection of cysteine

(Lead acetate test)

37-Covalent bond is formed at which level of protein’s structural organization?

(Primary structure)

38-Name the peptide hormones

 (ACTH, TRH, FSH, Glucagon, PTH, ADH, Oxytocin, Secretin, Pancreozymin, Cholecystokinin)

 39-What is the effect on the biological activity of a protein when exposed to UV light ?

 ( It will lose its biological activity since it will be denatured)

 40-Give two examples of protein misfolding causing disease?

 ( Prion’s and Alzheimer disease)

41-What is the class of casein ?

 (Class 1- complete protein)

42-What are the forces that stabilize quaternary structure of a protein ?

 (Mainly non covalent)

 43-Which amino acid acts as the best buffer of the plasma?

 (Histidine)

 44-What will be the product of decarboxylation of Tyrosine?

 (Tyramine)

 45-Why can’t albumin and majority proteins acquire the native configuration upon denaturation?    

 (Chaperones and other proteins assisting proper folding are not there)

 46-What are Beta bends?

 (Short loops to turn the direction of the beta sheets?

 47-What are the forces that stabilize the beta bends?

 (Hydrogen and electrostatic)

 48-Name a peptide to regulate the volume of urine excreted?

 (ADH)

 49-Which protein is present in the tendons and cartilages?

(Collagen)

 50-Name the storage proteins

 Ferritin, ceruloplasmin)





------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
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