MODIFIED MASTERING CHEMISTRY W/ ETEXT
8th Edition
ISBN: 9781323782507
Author: Bruice
Publisher: PEARSON
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Textbook Question
Chapter 21, Problem 76P
The primary structure of β-endorphin, a peptide containing 31 amino acids synthesized by the body to control pain, is shown here:
Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr-Leu-Phe-Lys-Asn-Ala-He-He-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-Glu
- a. What fragments are obtained as a result of treatment with each of the following?
1. trypsin
2. cyanogen bromide
3. chymotrypsin
- b. How much of the primary structure can be determined if the amino acids contained in each fragment (but not their sequence ) are known?
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The primary structure of b-endorphin, a peptide containing 31 amino acids synthesized by the body to control pain, is shown here:
Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr- Leu-Phe-Lys-Asn-Ala-Ile-Ile-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-Glu
What fragments are obtained as a result of treatment with chymotrypsin?
A peptide has the sequence
Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly
The p?a values for the peptide’s side chains, terminal amino groups, and carboxyl groups are provided in the table.
Amino acid
Amino pKa
Carboxyl pKa
Side‑chain pKa
glutamate
9.609.60
2.342.34
4.254.25
histidine
9.179.17
1.821.82
6.006.00
tryptophan
9.399.39
2.382.38
serine
9.159.15
2.212.21
glycine
9.609.60
2.342.34
leucine
9.609.60
2.362.36
arginine
9.049.04
2.172.17
12.4812.48
proline
10.9610.96
1.991.99
Calculate the net charge of the molecule at pH 11 and estimate the isoelectric point (pI)(pI) for this peptide.
Pentapeptide has a sequence of APEDS
Structure of pentapeptide in its proper ionization state at pH 7.0
what is the pI of pentapeptide?
Chapter 21 Solutions
MODIFIED MASTERING CHEMISTRY W/ ETEXT
Ch. 21.1 - a. Explain why, when the imidazole ring of...Ch. 21.2 - a. Which isomer(R)-alanine or (S)-alanineis...Ch. 21.2 - Prob. 4PCh. 21.3 - Prob. 5PCh. 21.3 - Prob. 6PCh. 21.3 - Draw the predominant form for glutamate in a...Ch. 21.3 - a. Why is the pKa of the glutamate side chain...Ch. 21.4 - Calculate the pI of each of the following amino...Ch. 21.4 - a. Which amino acid has the lowest pI value? b....Ch. 21.4 - Prob. 12P
Ch. 21.4 - Prob. 13PCh. 21.4 - Explain why the pI of lysine is the average of the...Ch. 21.5 - What aldehyde is formed when valine is treated...Ch. 21.5 - Prob. 16PCh. 21.5 - Prob. 17PCh. 21.5 - Prob. 18PCh. 21.5 - Prob. 19PCh. 21.6 - Why is excess ammonia used in the preceding...Ch. 21.6 - Prob. 21PCh. 21.6 - What amino acid is formed using the...Ch. 21.6 - Prob. 23PCh. 21.6 - What amino acid is formed when the aldehyde used...Ch. 21.7 - Esterase is an enzyme that catalyzes the...Ch. 21.8 - Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate...Ch. 21.8 - Draw the resonance contributors of the peptide...Ch. 21.8 - Which bonds in the backbone of a peptide can...Ch. 21.9 - An opioid pentapeptide has the following...Ch. 21.9 - What is the configuration about each of the...Ch. 21.9 - Glutathione is a tripeptide whose function is to...Ch. 21.10 - What dipeptides would be formed by heating a...Ch. 21.10 - Suppose you are trying to synthesize the dipeptide...Ch. 21.10 - Show the steps in the synthesis of the...Ch. 21.10 - a. Calculate the overall yield of bradykinin when...Ch. 21.11 - Show the steps in the synthesis of the...Ch. 21.13 - Prob. 37PCh. 21.13 - In determining the primary structure of insulin,...Ch. 21.13 - A decapeptide undergoes partial hydrolysis to give...Ch. 21.13 - Explain why cyanogen bromide does not cleave on...Ch. 21.13 - Indicate the peptides produced from cleavage by...Ch. 21.14 - Prob. 43PCh. 21.14 - Three peptides were obtained from a trypsin...Ch. 21.14 - Prob. 45PCh. 21.15 - How would a protein that resides in the nonpolar...Ch. 21.16 - a. Which would have the greatest percentage of...Ch. 21.17 - When apples that have been cut are exposed to...Ch. 21 - Glycine has pK2 values of 2.34 and 9.60. At what...Ch. 21 - Prob. 50PCh. 21 - A titration curve is a plot of the pH of a...Ch. 21 - Prob. 52PCh. 21 - Aspartame (its structure is on page 1007) has a pl...Ch. 21 - Draw the form of aspartate that predominates at...Ch. 21 - Show how phenylalanine can be prepared by...Ch. 21 - A professor was preparing a manuscript for...Ch. 21 - What aldehydes are formed when the following amino...Ch. 21 - Prob. 58PCh. 21 - Determine the amino acid sequence of a polypeptide...Ch. 21 - Prob. 60PCh. 21 - Prob. 61PCh. 21 - Which is the more effective buffer at...Ch. 21 - Identify the location and type of charge on the...Ch. 21 - Draw the product obtained when a lysine side chain...Ch. 21 - After the polypeptide shown below was treated with...Ch. 21 - Treatment of a polypeptide with 2-mercaptoethanol...Ch. 21 - Show how aspartame can be synthesized using DCCD.Ch. 21 - -Amino acids can be prepared by treating an...Ch. 21 - Reaction of a polypeptide with carboxypeptidase A...Ch. 21 - a. How many different octapeptides can be made...Ch. 21 - Glycine has pKa values of 2.3 and 9.6. Do you...Ch. 21 - A mixture of 15 amino acids gave the fingerprint...Ch. 21 - Write the mechanism for the reaction of an amino...Ch. 21 - Prob. 74PCh. 21 - Show how valine can be prepared by a. a...Ch. 21 - The primary structure of -endorphin, a peptide...Ch. 21 - A chemist wanted to test his hypothesis that the...Ch. 21 - Propose a mechanism for the rearrangement of the...Ch. 21 - A normal polypeptide and a mutant of the...Ch. 21 - Determine the amino acid sequence of a polypeptide...
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- Give the amino acid sequence of hexapeptides that produce the following sets of fragments upon partial acid hydrolysis: (a) Arg, Gly, Ile, Leu, Pro, Val gives Pro-Leu-Gly, Arg-Pro, Gly-Ile-Val (a) N, L, M, W, V2 gives V-L, V-M-W, W-N-Varrow_forwardWhich of the following peptides have a net positive chargeat pH 7? (a) Gly-Ser-Lys, (b) Pro-Leu-Ile, (c) Phe-Tyr-Asp.arrow_forwardDetermine the amino acid sequence of a polypeptide from the following data: Complete hydrolysis of the peptide yields Ala, Arg, Gly, 2 Lys, Met, Phe, Pro, 2 Ser, Tyr, and Val. Treatment with Edman’s reagent releases PTH-Val. Carboxypeptidase A releases Ala. Treatment with cyanogen bromide yields the following two peptides: 1. Ala, 2 Lys, Phe, Pro, Ser, Tyr 2. Arg, Gly, Met, Ser, Val Treatment with trypsin yields the following three peptides: 1. Gly, Lys, Met, Tyr 2. Ala, Lys, Phe, Pro, Ser 3. Arg, Ser, Val Treatment with chymotrypsin yields the following three peptides: 1. 2 Lys, Phe, Pro 2. Arg, Gly, Met, Ser, Tyr, Val 3. Ala, Serarrow_forward
- Which peptides is more likely to take up on alpha-helical structure? Explain. Top: Leu-Lys-Ala-Glu-Asn-Asp-Glu-Ala-Ala-Arg-Ala-Met-Ser-Glu-Ala Bottom: Cys-Arg-Ala-Gly-Gly-Phe-Pro-Trp-Asp-Gln-Pro-Gly-Tyr-Ser-Asnarrow_forwardHis-Met-Asp-Tyr-Phe-Ser within this peptide, which amino acid residue is the most hydrophobic and why?arrow_forwardCalculate an approximate pI for Peptide E-G-E-Aarrow_forward
- The peptide Proline-Serine-Alanine-Phenylalanine-Glutamine is present at pH 7. Draw the peptide and include stereochemistry.arrow_forwardAt very low pH, alanine is a diprotic acid that can be represented as H3N1-CH(CH3)-COOH. The pKa of the carboxyl group is 2.3, and the pKa of the UNH1 3 group is 9.7.(a) At pH 7, what fraction of the amino acid molecules dissolved in an aqueous solution will have the form H3N1-CH(CH3)-COO2?(b) What fraction of the molecules at this pH will havethe form H2N-CH(CH3)-COOH?arrow_forwardDetermine the amino acid sequence of a polypeptide from the following data:Complete hydrolysis of the peptide yields Ala, Arg, Gly, 2 Lys, Met, Phe, Pro, 2 Ser, Tyr, and Val.Treatment with Edman’s reagent releases PTH-Val.Carboxypeptidase A releases Ala. Treatment with trypsin yields the following three peptides:1. Gly, Lys, Met, Tyr 2. Ala, Lys, Phe, Pro, Ser 3. Arg, Ser, Valarrow_forward
- (a) Describe in detail how you will determine the primary structure of protein. (b)You have been given a mixture of lysine, histidine and cysteine. The isoelectric point of the amino acids are as follows:Histidine 7.64Lysine 9.74Cystenie 5.02Show how you will separate the mixture into the pure forms. State and describe any instrument that you will use to separate the components in the mixture.arrow_forwardDraw the structure of the tetrapeptide Asp-Arg-Val-Tyr. Please show the appropriate stereochemistry of the natural amino acids in the resulting peptide. Please draw all ionizable groups in their neutral form.arrow_forwardDraw the structure for each of the following peptides in their fully protonated forms. Indicate which protons are dissociable in the structure. a) Gly-Lys-Arg-Phe b) Y-D-S-C-Qarrow_forward
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