12.1 39. Arrange the following amino acid according to decreasing non-polarity (left to right).1- leucine2- phenylalanine3- valine4- alanineA. 1>3→4->2B. 4→3-2→1C. 3 2 1→4D. 2 1 3→440. A polypeptide with a net positive charge at physiologic pH (~7.4) most likely contains amino acids with R groups of whatype?A. Aliphatic R groupsB.Aromatic R groupsBasic R groupsС.D. Acidic R groupsE. All the above

Amino acids are biomolecules in which an alpha carbon is bonded to 4 groups. These groups are ; an…

Answered: 39. Arrange the following amino acid…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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1. A certain polypeptide was treated with trypsin and yielded the following Fragments: Leu-Glu Gly-Tyr-Asn-Arg Gln-Ala-Phe-Val-Lys The same polypeptide was treated with chymotrypsin and yielded the following fragments: Gln-Ala-Phe Asn-Arg-Leu-Glu Val-Lys-Gly-Tyr What is the amino acid sequence of this polypeptide? Instructions Make use of the table below to determine the sequence of the mystery protein.
1 Draw the following polypeptide: Met- Tyr-Val-Ser-Asn 2A Draw the hydrolysis of a dipeptide consisting of phenylaline and glutamic acid. 2B What are the fuctional group present in the side chains of the amino acids.( phenylalanine and glutamic acid) 2C are the sidechains in part 2B hydrophobic or polar 2D where would you expect to find them ( surface or interior of a protein) ? why ?
1. Sickle cell anemia results from a substitution of a valine for a glutamic acid. What do you expect the effect might be if the mutation were to have placed a leucine at that site? An aspartic acid? 2. Of the following amino acids, glycine, isoleucine, and lysine, which would you expect to be the most soluble in an acidic aqueous solution? Which the least? 3. How many structural isomers could be formed from a molecule with the formula C5H12? C4H8?
1. What is the isoelectric point (pI) of lysine which has pKa values of 2.1 for the α carboxyl group, 9.7 for the α amino group and 10.5 for the side chain amino group? 2. Which of the following is most likely to be found on the exterior of a protein? A) Pro B) Trp C) Ser D) Glu 3. The type of reaction that forms a peptide bond is A) Elimination B) Hydrolysis C) Nucleophilic substitution D) Condensation
2. A group of peptides that influence nerve transmission in certain parts of the brain have been isolated from normal brain tissue. These peptides are known as opioids. Using the information below, determine the amino acid sequence of this particular opioid: ● Complete hydrolysis by HCl at 100° C followed by amino acid hydrolysis analysis indicated the presence of Gly, Leu, Phe, and Tyr, in a 2:1:1:1 ratio. ● Treatment of the peptide with FNDB followed by complete hydrolysis indicated the presence of 2,2-dinitrophenyl derivative of tyrosine. No free tyrosine could be found. ● Complete digestion of the peptide with chymotrypsin yielded free tyrosine and leucine, plus a tripeptide containing Phe and Gly in a 1:2 ratio. Instructions Make use of the table below to determine the sequence of the mystery protein:
2. A mixture of the following amino acids (glu, leu, val, arg, ser, phe) was obtained upon complete hydrolysis of a hexapeptide. a. Edman’s reagent releases leucine b. Hexapeptide with carboxypeptidase releases serine. c. Hexapeptide with trypsin forms a tripeptide A with leucine at the N terminal and tripeptide B with valine at the N terminal. d. Tripeptide A with carboxypeptidase releases arginine and a dipeptide with glutamic acid at C terminal. e. Tripeptide B with chymotrypsin form releases serine and another dipeptide. Give: 1. the amino acid sequence of tripeptide A and B. 2. the amino acid sequence in the above hexapeptide.
24. The sidechain of the amino acid serine is -CH2-OH. Serine is classified as this type of amino acid (side chain): a) hydrophobic and nonpolar b) hydrophilic and polar c) acidic d) basic
1. Analysis of a peptide antibiotic purified from a strain of Bacillus brevii resulted in the following significant information: - Complete hydrolysis of the peptide yielded equimolar amounts of Leu, Orn, Phe, Pro, and Val - Molecular weight of the peptide was estimated to be aroung 1,200 Da - The peptide failed to undergo hydrolysis when treated with carboxypeptidase - Partial hydrolysis and then chromatographic separation of products yielded the following di- and tripeptides: Leu-Phe, Phe-Pro, Orn-Leu, Val-Orn, Val-Orn-Leu, Phe-Pro-Val, Pro-Val- - Orn Treament with dinitrofluorobenzene (DNFB) followed by complete hydrolysis yielded only free amino acids and the DNFB-derivatized ornithine at its side chain By using the above information, deduce the amino acid sequence of this peptide antibiotic. Write the final peptide sequence using 3-letter abbreviations. Show the complete and step by step solution.
2. The endorphins are a group of naturally occurring neurotransmitters that act in a manner like morphine to control pain. Research has shown that the biologically active parts of the endorphin molecules are simple pentapeptides called enkephalins. Draw the structure of the methionine enkephalin with the sequence Tyr-Gly-Gly-Phe-Met. Identify the N- terminal and C-terminal amino acids. 3. Bradykinin is a nonapeptide that stimulates smooth muscle contraction, dilates blood vessels, causes pain, and is a component of bee venom. Give the IUPAC name of the nonapeptide. 4. Some researchers feel that the “high” experienced by runners may be due to the brain’s synthesis of peptides. Explain why this theory might be a reasonable explanation
Polylysine adopts a random structure in solution at physiological pH (i.e. 7.4). Given that the e-amino group of lysine has a pKa of 10.5, under what circumstances do you think polylysine will form an a-helix? Give an explanation for your decision. Given the pKa of the side-chain COOH group, under what circumstances would you anticipate polyglutamate to form an a-helix?
4. Write the structure of each of the following peptides at pH 7: a. Alanylphenylalanine b. Threonylcysteine c. Phenylalanyltryrosylleucine d. Glycylvalylserine 5. Tripeptides are composed of three amino acids linked by peptide bonds. Given a set of amino acids, you can make several different tripeptides. a. Use the three-letter shorthand notations to name all the tripeptides that can be made from serine, tyrosine, and glycine. Each amino acid will be used once in each tripeptide. b. Draw the complete structure of the tripeptides that have glycine as the N-terminal amino acid.
At physiological pH (i.e. 7.4), polylysine assumes a random structure in solution. Given that the pKa for the e-amino group of lysine is 10.5, under what conditions would you expect polylysine to form an a-helix? Explain your reasoning. Under what conditions would you expect polyglutamate to form an a-helix, given that the pKa for the side-chain COOH group is 4.3?

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