Daily Test- 1 (23rd April 2015)- (Protein Part-C Questions)

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Daily Test-1:

Daily Test-1 Protein Questions

Question No 1:

Question No 1 What is the approximate molecular weight of a protein with 682 amino acid residues in a single polypeptide chain ? 75000 85000 95000 None

Question No 2:

Question No 2 A quantitative amino acid analysis reveals that bovine serum albumin (BSA) contains 0.58% tryptophan ( Mr 204) by weight. Calculate the minimum molecular weight of BSA (i.e., assuming there is only one tryptophan residue per protein molecule ). (b) Gel filtration of BSA gives a molecular weight estimate of 70,000. How many tryptophan residues are present in a molecule of serum albumin ? 32000D 42000D 52000D 62000D 1 2 3 4

Question No 3 :

Question No 3 A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein gives three bands with molecular masses of 180, 160, and 60 kDa . When electrophoresis is carried out in the presence of SDS and dithiothreitol , three bands are again formed, this time with molecular masses of 160, 90, and 60 kDa . Determine the subunit composition of the protein.   1 2 3 4

Question No 4:

Question No 4 A peptide has the sequence What is the net charge of the molecule at pH 3, 8, and 11 ? (b) Estimate the pI for this peptide. +2, 0 , -1 0, +2, -1 -1, 0, +2, +2, -1, 0 6.8 7.8 10 12

Question No 5:

Question No 5 One method for separating polypeptides makes use of their different solubilities . The solubility of large polypeptides in water depends upon the relative polarity of their R groups , particularly on the number of ionized groups: the more ionized groups there are, the more soluble the polypeptide. Which of each pair of the polypeptides that follow is more soluble at the indicated pH? (a) ( Gly ) 20 or ( Glu ) 20 at pH 7.0 (b) (Lys– Ala ) 3 or ( Phe –Met) 3 at pH 7.0 (c) ( Ala – Ser – Gly ) 5 or ( Asn – Ser –His) 5 at pH 6.0 (d) ( Ala –Asp– Gly ) 5 or ( Asn – Ser –His)5 at pH 3.0 Glu , Lys-Ala, Asn - Ser -His, Asn - Ser -His Glu , Lys-Ala, Ala- Ser - Gly , Asn - Ser -His Glu , Lys-Ala, Asn - Ser -His, Ala-Asp-His Gly , Lys-Ala, Asn - Ser -His, Asn - Ser -His

Question No 6:

Question No 6 At pH 7.0, in what order would the following three peptides be eluted from a column filled with a cation -exchange polymer? Their amino acid compositions are: Protein A : Ala 10%, Glu 5%, Ser 5%, Leu 10%, Arg 10%, His 5%, Ile 10%, Phe 5%, Tyr 5%, Lys 10%, Gly 10%, Pro 5%, and Trp 10%. Protein B : Ala 5%, Val 5%, Gly 10%, Asp 5%, Leu 5%, Arg 5%, Ile 5%, Phe 5%, Tyr 5%, Lys 5%, Trp 5%, Ser 5%, Thr 5%, Glu 5%, Asn 5%, Pro 10%, Met 5%, and Cys 5%. Protein C: Ala 10%, Glu 10%, Gly 5%, Leu 5%, Asp 10%, Arg 5%, Met 5%, Cys 5%, Tyr 5%, Phe 5%, His 5%, Val 5%, Pro 5%, Thr 5%, Ser 5%, Asn 5%, and Gln 5%. A, B, C B, C, A C, B, A B, A, C

Question No 7:

Question No 7 Which of the following peptides is more likely to take up an α-helical structure, and why? (a) LKAENDEAARAMSEA, ΔGº of 13 kJ/ mol (b) CRAGGFPWDQPGTSN, ΔGº of 41 kJ/ mol A B Both None

Question No 8:

Question No 8 In what order will the following amino acids be eluted from a column of P-cellulose ion exchange resin by a buffer at pH 6: arginine , aspartic acid, histidine, and leucine ? Aspartate,histidine , arginine Aspartate, leucine, arginine leucine, histidine, arginine Aspartate, leucine, histidine, arginine

Answer Key:

Answer Key 1-1 2 (a) 1, (b) 2 3-4 4 (a) a, (b) b 5-1 6-3 7-1 8-4

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