Essential Organic Chemistry (3rd Edition)
3rd Edition
ISBN: 9780321937711
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Textbook Question
Chapter 21, Problem 31P
The amino acid sequences of peptide fragments obtained from a normal protein were compared with those obtained from the same protein synthesized by a defective gene. They were found to differ in only one peptide fragment. Their amino acid sequences are shown here:
Normal: Gln-Tyr-Gly-Thr-Arg-Tyr-Val
Mutant: Gln-Ser-Glu-Pro-Gly-Thr
- a. What is the defect in DNA?
- b. It was later determined that the normal peptide fragment is an octapeptide with a C-terminal Val-Leu. What is the C-terminal amino acid of the mutant peptide?
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Chemistry
1a. The lack of an asymmetric carbons and ease of rotation make glycine rich protein sequences:
a. Fibrous
b. Helical
c. Cyclic
d. Flexible
e. Globular
1b. Introducing D-amino acids into peptides can be useful as a strategy to:
a. Change pKa
b. Reduce thermal stability
c. Alter ionic strength
d. Slow degradation
e. Increase solubility
1c. Cellulose is not useful dietary carbohydrate because humans:
a. Don’t have sufficient non-mitochondrial ATP
b. Lack a 1,4-beta glycosidase
c. Can’t digest branched chain carbohydrates
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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.
5
ased on molecular weights of purified (no beta-Me) and (beta-Me) sample, which are 97.4 kDa and 47.2 kDa, what can be said about the number and size of the protein monomers, as well as the nature of the bonds holding together the complete quaternary structure of the proteins?
Chapter 21 Solutions
Essential Organic Chemistry (3rd Edition)
Ch. 21.1 - Draw the structure for each of the following: a....Ch. 21.3 - If one of the strands of DNA has the following...Ch. 21.4 - The 2,3-cyclic phosphodiester that is formed...Ch. 21.5 - Using a dark line for the original parental DNA...Ch. 21.7 - Why do both thymine and uracil specify the...Ch. 21.9 - If methionine is always the first amino acid...Ch. 21.9 - Four Cs occur in a row in the segment of mRNA...Ch. 21.9 - UAA is a stop codon. Why does the UAA sequence in...Ch. 21.9 - A change in which base of a codon would be least...Ch. 21.9 - Write the sequences of bases in the sense strand...
Ch. 21.9 - List the possible codons on mRNA that specify each...Ch. 21.10 - Adenine can be deaminated to hypoxanthine, and...Ch. 21.10 - Explain why thymine cannot be deaminated.Ch. 21.12 - Which of the following base sequences would most...Ch. 21 - Draw structures for the following: a....Ch. 21 - What nonapeptide is coded for by the following...Ch. 21 - What is the sequence of bases in the template...Ch. 21 - What is the sequence of bases in the sense strand...Ch. 21 - What would be the C-terminal amino acid if the...Ch. 21 - What would be the base sequence of the segment of...Ch. 21 - Propose a mechanism for the following reaction:Ch. 21 - A segment of DNA has 18 base pairs. It has 7...Ch. 21 - Match the codon with the anticodon: Codon: AAA GCA...Ch. 21 - Using the single-letter abbreviations for the...Ch. 21 - Indicate whether each functional group of the five...Ch. 21 - Using the A and D designations in Problem 25,...Ch. 21 - Which of the following pairs of dinucleotides are...Ch. 21 - If an mRNA contained only U and G in random...Ch. 21 - Why is the codon a triplet rather than a doublet...Ch. 21 - Human immunodeficiency virus (HIV) is the...Ch. 21 - The amino acid sequences of peptide fragments...Ch. 21 - Which cytosine in the following sense strand of...Ch. 21 - Prob. 33PCh. 21 - Why does DNA not unravel completely before...Ch. 21 - The first amino acid incorporated into a...
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- Three peptides were obtained from a trypsin digestion of two different polypeptides. In each case, indicate the possible sequences from the given data and tell what further experiment should be carried out in order to determine the primary structure of the polypeptide. a. polypeptide I: 1. Val-Gly-Asp-Lys 2. Leu-Glu-Pro-Ala-Arg 3. Ala-Leu-Gly-Asp b. polypeptide II: 1. Val-Leu-Gly-Glu 2. Ala-Glu-Pro-Arg 3. Ala-Met-Gly-Lysarrow_forwardThree peptides were obtained from a trypsin digestion of two different polypeptides. indicate the possible sequences from the given data and tell what further experiment should be carried out in order to determine the primary structure of the polypeptide. polypeptide I: 1. Val-Gly-Asp-Lys 2. Leu-Glu-Pro-Ala-Arg 3. Ala-Leu-Gly-Asparrow_forwardConsider the following peptide : Phe – Glu – Ser – Met and Val – Trp – Cys – Leu. Do these peptides have different net charges at (a) pH 1? (b) pH 7? Indicate the charges at both pH valuesarrow_forward
- Important steps in sequencing pure proteins include all of these except: a. Determining the amino acids on the ends of the smaller peptides b. Determining the amino acids on the ends of the protein c. Determining the isoionic pH of the protein d. Determining the amino acid composition e. Breaking the protein into smaller peptides It is impossible to sequence a protein if you do not have overlapping sequences to work with. A. True B. Falsearrow_forwardReport the isoelectric point of the peptide, Gly-Asp-Lys-Ile?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_forward
- His-Met-Asp-Tyr-Phe-Ser within this peptide, which amino acid residue is the most hydrophobic and why?arrow_forwardDecide if the side chains of the following peptides are nonpolar or polar, and label the hydrophobic and hydrophilic end of each peptide.a. VLLFGEDEKb. RKYSFLGAAarrow_forwardA peptide has the following amino acid composition: 2 Met, 2 Phe, 2 Glu, 1 Arg, 1 Lys, 1 Val, 1 Leu, 1 Gly, 1 Ser Reaction of the intact peptide with dansyl chloride followed by acid hydrolysis creates a derivative of Met. A specific cleavage of the intact peptide produces fragments with the following sequences: Fragment A: Glu-Gly-Lys-Phe Fragment B: Met-Ser-Leu-Arg Fragment C: Met-Val-Glu-Phe What information do this result give about the sequence of the peptide? Explain how you arrived on your answer. a) The sequence is: Met-Val-Glu-Phe-Glu-Gly-Lys-Phe-Met-Ser-Leu-Arg b) The sequence is: Met-Ser-Leu-Arg-Met-Val-Glu-Phe-Glu-Gly-Lys-Phe c) The sequence is: Met-Val-Glu-Phe-Met-Ser-Leu-Arg-Glu-Gly-Lys-Phe d) The sequence is: Met-Ser-Leu-Arg-Glu-Gly-Lys-Phe-Met Val-Glu-Phearrow_forward
- (a) Redraw the tripeptide in zwitterionic form (b) Explain how ESI-MS can be used to determine which amino acid is in the middle of the sequence.arrow_forwardConsider a tripeptide (a peptide that's only 3 amino acids long) composed of one molecule each of lysine, leucine, and the hypothetical amino acid lupine (which doesn't actually exist, so don't try to look it up). Lupine has an ionizable side group with a pKa of 6.3. When this tripeptide is dissolved in an aqueous solution at pH 5.0, the net charge on the molecule is +2. Give the charge on the protonated form of the lupine side group, and the charge on the deprotonated form of the lupine side group.arrow_forwardAs a genetic engineer, you have been given the following task:alter a protein’s structure by converting a specific amino acidsequence that forms an extended a-helix to one that formsa b-barrel. What types of amino acid are probably in thea-helix, and which ones would you need to substitute?arrow_forward
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