Organic Chemistry (9th Edition)
9th Edition
ISBN: 9780321971371
Author: Leroy G. Wade, Jan W. Simek
Publisher: PEARSON
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Chapter 24, Problem 24.40SP
Lipoic acid is often found near the active sites of enzymes, usually bound to the peptide by a long flexible amide linkage with a lysine residue.
- a. Is lipoic acid a mild oxidizing agent or a mild reducing agent? Draw it in both its oxidized and reduced forms.
- b. Show how lipoic acid might react with two Cys residues to form a disulfide bridge.
- c. Give a balanced equation for the hypothetical oxidation or reduction, as you predicted in part (a), of an
aldehyde by lipoic acid.
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1. (a) Draw a circle around one amino acidin the structure. (
b) Draw a box around one amino acid side chain.
(c) Indicate whether the side chain you chose is hydrophobic or hydrophilic.
(d) Draw an arrow pointing to a peptide bond
2. If the peptide segment shown above was part of a beta sheet, which of its functional groups would be involved in forming and stabilizing the beta sheet?
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Chapter 24 Solutions
Organic Chemistry (9th Edition)
Ch. 24.2A - Draw three-dimensional representations of the...Ch. 24.2A - Prob. 24.2PCh. 24.2B - The herbicide glyphosate (Roundup) kills plants by...Ch. 24.4 - Draw the structure of the predominant form of a....Ch. 24.4 - Draw the resonance forms of a protonated guanidino...Ch. 24.4 - Although tryptophan contains a heterocyclic amine,...Ch. 24.4 - Prob. 24.7PCh. 24.4 - Prob. 24.8PCh. 24.5A - Show how the following amino acids might be formed...Ch. 24.5B - Prob. 24.10P
Ch. 24.5C - Prob. 24.11PCh. 24.5C - Show how you would use a Strecker synthesis to...Ch. 24.6 - Suggest how you would separate the free i-ammo...Ch. 24.7A - Propose a mechanism for the acid-catalyzed...Ch. 24.7A - Give equations for the formation and...Ch. 24.7B - Prob. 24.16PCh. 24.7C - Prob. 24.17PCh. 24.8B - Draw the complete structures of the following...Ch. 24.9C - Prob. 24.19PCh. 24.9C - Prob. 24.20PCh. 24.9C - Prob. 24.21PCh. 24.9E - Prob. 24.22PCh. 24.9E - Prob. 24.23PCh. 24.10A - Propose a mechanism for the coupling of acetic...Ch. 24.10B - Show how you would synthesize Leu-Gly-Ala-Val-Phe...Ch. 24.10B - Show how solid-phase peptide synthesis would be...Ch. 24 - a. The isoelectric point (pl) of phenylalanine is...Ch. 24 - Prob. 24.28SPCh. 24 - Prob. 24.29SPCh. 24 - Prob. 24.30SPCh. 24 - Prob. 24.31SPCh. 24 - Suggest a method for the synthesis of the...Ch. 24 - Prob. 24.33SPCh. 24 - Write the complete structures for the following...Ch. 24 - The following structure is drawn in an...Ch. 24 - Prob. 24.36SPCh. 24 - Prob. 24.37SPCh. 24 - Show the steps and intermediates in the synthesis...Ch. 24 - Prob. 24.39SPCh. 24 - Lipoic acid is often found near the active sites...Ch. 24 - Prob. 24.41SPCh. 24 - Prob. 24.42SPCh. 24 - Prob. 24.43SPCh. 24 - Complete hydrolysis of an unknown basic...Ch. 24 - Prob. 24.45SPCh. 24 - Prob. 24.46SPCh. 24 - Prob. 24.47SP
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- Another method to form a peptide bond involves a two-step process:[1] Conversion of a Boc-protected amino acid to a p-nitrophenyl ester.[2] Reaction of the p-nitrophenyl ester with an amino acid ester.a. Why does a p-nitrophenyl ester “activate” the carboxy group of the first amino acid to amide formation? b. Would a p-methoxyphenyl ester perform the same function? Why or why not?arrow_forwardDraw Tryptophan in a peptide bond. Explain all of the bonds using valence bond theory (VBT). Next, explain where VBT fails and how molecular orbital theory is a better description of key regions of this amino acid and the peptide bonds it forms with other residuesarrow_forwardindicate the RIGHT alternative: (a) The Zwitterion form of an amino acid exists only at a point pH value. (b) In a peptide bond there is free rotation at the C-N bond. (c) In a polypeptide, the terminal carboxyl group may be present in its amide form. (d) At a pH greater than pI, an amino acid tends to move towards the cathode in an electrophoresis. (e) At any pH below pI, the predominant form of an amino acid is negatively charged.arrow_forward
- The amino acid (S)-alanine has the physical characteristics listed under the structure. a.What is the melting point of (R)-alanine? b.How does the melting point of a racemic mixture of (R)- and (S)-alanine compare to the melting point of (S)-alanine? c. What is the specific rotation of (R)-alanine, recorded under the same conditions as the reported rotation of (S)-alanine? d.What is the optical rotation of a racemic mixture of (R)- and (S)-alanine? e.Label each of the following as optically active or inactive: a solution of pure (S)alanine; an equal mixture of (R)- and (S)-alanine; a solution that contains 75% (S)- and 25% (R)-alanine.arrow_forward. True/ False A. Amino acids found in the living systems are generally in the D-form B. The R-group attached to alfa carbon atom of amino acids are unique for each amino acids. C. Of the 20 essential amino acids, glycine is the only amino acid which is achiral. D. Ions of heavy metals Hg2+ or Pb2+ denature proteins by combining with the amino groups. E. Denaturation of protein involves the breakdown of secondary, tertiary and quaternary structure. F. Cysteine is the only amino acid that can form a disulfide bridge. G. Both the poly saccharides and proteins are polymers. H. Hydrogen bonding is responsible for the secondary structure of Proteins. I. When proteins are hydrolyzed, smaller peptides and amino acids are produced. J. When simple lipids are hydrolyzed glycerol an alcohol as well as fatty acids and their salts are produced.arrow_forwardWrite out the steps needed to synthesize the following peptide using the Merrifield method.arrow_forward
- Another method to form a peptide bond involves a two-step process Reaction of the p-nitrophenyl ester with an amino acid ester. Why does a p-nitrophenyl ester “activate” the carboxy group of thefirst amino acid to amide formation?arrow_forwardConsider the following tetrapeptide, written in a sequence according to normal convention, from left to right: Residue 1 is acidic; Residue 2 is cysteine (an amino acid containing a –CH2SH R-group); Residue 3 is proline (a large hydrophobic amino acid); Residue 4 is basic. Of the following four general statements, which one is TRUE regarding this tetrapeptide? This tetrapeptide does not have the ability to form a disulfide linkage with an identical tetrapeptide. Residue 2 belongs to the amino acid category known as "basic." 3 of these 4 responses are correct This tetrapeptide could be part of an alpha-helix, since the large size of the proline would not have any impact on the consistency of the spiral shape. The acidic residue (Residue #1) is at the amino terminus of this tetrapeptide.arrow_forwardBy using only amide/Peptide bond forming rxn and a lKylation rxns. Provide all the reaction steps with the reagent needed and conditions with out showing the mechanism for each step to form the product. Note: Use protecting groups like (Boc, Fmoc, and others) H2NNH2+arrow_forward
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