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Chapter 21: Q38P (page 1015)

Question: In determining the primary structure of insulin, what would lead you to conclude that insulin had more than one polypeptide chain?

Short Answer

Expert verified

The answer is:

The treatment of insulin with Edman’s reagent would give two PTH amino acids.

Step by step solution

01

Step-by-Step Solution Step 1: Insulin

Human pancreas secretes insulin which controls the blood sugar level. It is composed of a chain of amino acids called peptides and has a single polypeptide chain.

02

Explanation

Insulin comprises of two peptide chains. On treatment with the Edman’s reagent (heptfluorobutyric acid) would release two PTH amino acids in approximately equal amounts.

Hence on the determination of the primary structure of insulin, it can be concluded that there will be more than one polypeptide in it.

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Most popular questions from this chapter

Explain why the pI values of tyrosine and cysteine cannot be determined by the method described on page 995.

Explain the difference in the \({\bf{p}}{{\bf{K}}_{\bf{a}}}\) values of the carboxyl groups of alanine, serine, and cysteine.

After the polypeptide shown below was treated with maleic anhydride, it was hydrolyzed by trypsin. (After a polypeptide is treated with maleic anhydride,

trypsin will cleave the polypeptide only on the C-side of arginine.)

Gly-Ala-Asp-Ala-Leu-Pro-Gly-Ile-Leu-Val-Arg-Asp-Val-Gly-Lys-Val-Glu-Val-Phe-Glu-Ala-Gly-

Arg-Ala-Glu-Phe-Lys-Glu-Pro-Arg-Leu-Val-Met-Lys-Val-Glu-Gly-Arg-Pro-Val-Gly-Ala-Gly-Leu-Trp

a. After a polypeptide is treated with maleic anhydride, why does trypsin no longer cleave it on the C-side of lysine?

b. How many fragments are obtained from the polypeptide?

c. In what order will the fragments be eluted from an anion-exchange column using a buffer of pH = 5?

Draw the product obtained when a lysine side chain in a polypeptide reacts with maleic anhydride.

A mixture of amino acids that do not separate sufficiently when a single technique is used can often be separated by two-dimensional chromatography.In this technique, the mixture of amino acids is applied to a piece of filter paper and separated by chromatographic techniques. The paper is then rotated90°,and the amino acids are further separated by electrophoresis, producing a type of chromatogram called a fingerprint.Identify the spots in the fingerprint obtainedfrom a mixture of Ser, Glu, Leu, His, Met, and Thr.
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