Organic Chemistry
4th Edition
ISBN: 9780073402772
Author: Janice G. Smith
Publisher: MCG
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Textbook Question
Chapter 29, Problem 29.39P
a. Draw the structure of the tripeptide A–A–A, and label the two ionizable
b. What is the predominant form of A–A–A at
c. The pKa values for the two ionizable functional groups (3.39 and 8.03) differ considerably from the pKa values of alanine (2.35 and 9.87; see Table 29.1). Account for the observed pKa differences.
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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
d. Loose lactase as they mature
e. Can’t absorb pentise subunits
In the case of serine, threonine and tyrosine they have the -OH group in their residue. I'm wondering even though all of them has the -OH groups in their residue. but only the tyrosine has the pKa value with the -OH grouup.
a. State the glycine species at pKa1 and pKa2.
b. Why a pH value is equal to pKa value in the middle of titration?
c. State the functional group (s) at pKa1 and pKa2.
d. If aspartic acid is used, determine how many pKa values will be obtained and give reasons.
e. Compare the pKa of glycine and pKa of acetic acid and state which compound is a strong acid or weak acid. Explain why.
Chapter 29 Solutions
Organic Chemistry
Ch. 29 - Prob. 29.1PCh. 29 - Problem 29.2
What form exists at the isoelectric...Ch. 29 - Problem 29.3
Explain why the of the group of an...Ch. 29 - Problem 29.5
What -halo carbonyl compound is...Ch. 29 - Problem 29.6
The enolate derived from diethyl...Ch. 29 - Problem 29.7
What amino acid is formed when is...Ch. 29 - Problem 29.8
What aldehyde is needed to synthesize...Ch. 29 - Prob. 29.8PCh. 29 - Prob. 29.9PCh. 29 - Prob. 29.10P
Ch. 29 - Prob. 29.11PCh. 29 - Problem 29.13
What alkene is needed to synthesize...Ch. 29 - Problem 29.14
Draw the structure of each peptide....Ch. 29 - Name each peptide using both the one-letter and...Ch. 29 - Prob. 29.15PCh. 29 - Prob. 29.16PCh. 29 - Problem 29.18
Glutathione, a powerful antioxidant...Ch. 29 - Problem 29.19
Draw the structure of the...Ch. 29 - Problem 29.20
Give the amino acid sequence of an...Ch. 29 - a What products are formed when each peptide is...Ch. 29 - Prob. 29.21PCh. 29 - Devise a synthesis of each peptide from amino acid...Ch. 29 - Devise a synthesis of the following dipeptide from...Ch. 29 - Prob. 29.24PCh. 29 - Consider two molecules of a tetrapeptide composed...Ch. 29 - What types of stabilizing interactions exist...Ch. 29 - Prob. 29.27PCh. 29 - Draw the product formed when the following amino...Ch. 29 - With reference to the following peptide: a...Ch. 29 - Devise a synthesis of the following dipeptide from...Ch. 29 - Prob. 29.31PCh. 29 - Prob. 29.32PCh. 29 - Histidine is classified as a basic amino acid...Ch. 29 - Tryptophan is not classified as a basic amino acid...Ch. 29 - What is the structure of each amino acid at its...Ch. 29 - To calculate the isoelectric point of amino acids...Ch. 29 - What is the predominant form of each of the...Ch. 29 - 29.37 What is the predominant form of each of the...Ch. 29 - a. Draw the structure of the tripeptide A–A–A, and...Ch. 29 - Draw the organic product formed when the amino...Ch. 29 - 29.39 Draw the organic products formed in each...Ch. 29 - 29.40 What alkyl halide is needed to synthesize...Ch. 29 - 29.41 Devise a synthesis of threonine from diethyl...Ch. 29 - 29.42 Devise a synthesis of each amino acid from...Ch. 29 - Prob. 29.45PCh. 29 - Prob. 29.46PCh. 29 - Prob. 29.47PCh. 29 - Prob. 29.48PCh. 29 - Prob. 29.49PCh. 29 - 29.48 Brucine is a poisonous alkaloid obtained...Ch. 29 - Prob. 29.51PCh. 29 - Prob. 29.52PCh. 29 - Draw the structure for each peptide: (a) Phe–Ala;...Ch. 29 - 29.52 For the tetrapeptide Asp–Arg–Val–Tyr:
a....Ch. 29 - Prob. 29.55PCh. 29 - Explain why a peptide CN bond is stronger than an...Ch. 29 - Prob. 29.57PCh. 29 - 29.55 Draw the amino acids and peptide fragments...Ch. 29 - Prob. 29.59PCh. 29 - Prob. 29.60PCh. 29 - Prob. 29.61PCh. 29 - 29.59 An octapeptide contains the following amino...Ch. 29 - Prob. 29.63PCh. 29 - Prob. 29.64PCh. 29 - Draw all the steps in the synthesis of each...Ch. 29 - 29.62 Write out the steps for the synthesis of...Ch. 29 - 29.64 Another method to form a peptide bond...Ch. 29 - Prob. 29.68PCh. 29 - Prob. 29.69PCh. 29 - Which of the following amino acids are typically...Ch. 29 - After the peptide chain of collagen has been...Ch. 29 - Prob. 29.72PCh. 29 - Prob. 29.73PCh. 29 - 29.70 The anti-obesity drug orlistat works by...Ch. 29 - Prob. 29.75P
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- Leuprolide is a synthetic nonapeptide used to treat both endometriosis in women and prostate cancer in men. (a) Both C-terminal and N-terminal amino acids in leuprolide have been structurally modified. Identify the modifications. (b) One of the nine amino acids in leuprolide has d stereochemistry rather than the usual L. Which one? (c) Write the structure of leuprolide using both one- and three-letter abbreviations. (d) What charge would you expect leuprolide to have at neutral pH?arrow_forwardAccording to the paper, F486 is a phenylalanine residue (i.e., an amino acid that is part of a chain that forms a protein) on SARS-CoV-2. It has an important interaction with ACE2 (best seen in Fig. 1(C) and Fig. 2(A)). Looking at this phenylalanine and the green residues surrounding it, which statement best describes the interaction that could be occurring? a) It forms a hydrogen bond with Y83. b) It forms a dipole-dipole interaction with M82. c) It forms London dispersion forces with surrounding residues. d) It encounters repulsions from surrounding residues.arrow_forwardAlanine has pKa values of 2.34 and 9.69. Therefore, alanine exists predominately as a zwitterion in an aqueous solution with pH > ____ and pH < ____.arrow_forward
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- (b) Describe how the charge of some amino groups in a protein might differ at pH 9.0 and pH 5.0. the charge on the amino group will differ at pH 5 and pH 9 which will depend on the pKa of the amino acid. (c) Describe how the charge of some carboxyl groups in a protein might differ at pH 9.0 and pH 5.0. charge on carboxyl group will differ at pH 5 and pH 9 which will depend on the pKa of the amino acid. (d) Given your answers to parts (b) and (c), what kind of intramolecular interactions in beta-galactosidase are most likely to be affected by a change in pH from 9.0 to 5.0? (e) Could the interactions you mention in part (d) affect the catalytic activity of beta-galactosidase?arrow_forwardExplain why the pKa of the - NH3+ group of an a-amino acid is lower than the pKa of the ammonium ion derived from a 1° amine (RNH3+). For example the pKa of the - NH3+ group of alanine is 9.87 but the pKa of CH3NH3+ is 10.63.arrow_forwardThe pKa for the side chain amino group in lysine is 10.4. If we were working at physiological pH 7.4, what would be the ratio of the protonated to unprotonated versions of lysine? a. 1000:1 b. 3:1 c. 1:1000 d. 1:3arrow_forward
- A tripeptide on hydrolysis produced glycine, alanine and leucine. The structures of these amino acids are shown below. On reaction with Edman’s reagent, leucine was released as the phenylhydantoin. Treatment of the tripeptide with carboxypeptidase gave glycine. Draw the structure of the tripeptide.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_forwardCalculate an approximate pI for Peptide E-G-E-Aarrow_forward
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