Organic Chemistry (8th Edition)
8th Edition
ISBN: 9780134042282
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Textbook Question
Chapter 21.4, Problem 14P
Explain why the pI of lysine is the average of the pKa, values of its two protonated amino groups.
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Explain why the pI of lysine is the average of the pKa values of its two protonated amino groups.
Give the structure of simplest optically active amino acid.
the pKa values for phenylalanine are 1.83 (carboxyl group) and 9.13 (amino group). Use the Henderson-hasselbach equation to determine the ratio of the acidic and basic forms of each of the ionizing groups of phenylalanine at neutral pH. Based on this, draw the predominant structure of phenylalanine at neutral pH.
Chapter 21 Solutions
Organic Chemistry (8th Edition)
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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- What special role does the amino acid cysteine have in the peptides vasopressin and oxytocin?arrow_forwardOn complete hydrolysis, a polypeptide gives two alanine, one leucine, one methionine, one phenylalanine, and one valine residue. Partial hydrolysis gives the following fragments: Ala-Phe, Leu-Met, Val-Ala, Phe-Leu. It is known that the first amino acid in the sequence is valine and the last one is methionine. What is the complete sequence of amino acids?arrow_forwardConsider the tripeptide leucylvalyltryptophan. a. Specify its structure using three-letter symbols for the amino acids. b. How many peptide bonds are present within the peptide? c. Which of the amino acid residues has the largest R group? d. Which of the amino acid residues, if any, has a basic side chain?arrow_forward
- At room temperature, amino acids are solids with relatively high decomposition points. Explain why.arrow_forwardA given glycine solution was titrated against NaOH and pH of the final solution was 4.8. Given that pKa1 and pKa2 of glycine are 2.34 and 9.60, respectively. Calculate the concentration of the dissociated amino acid in terms of the undissociated amino acid, if [x] and [y] are the concentrations of dissociated and undissociated amino acid, respectively.arrow_forwardDraw the sequential transition of glutamic acid as it passes from its fully protonated form to its fully deprotonated form as the pH rises. If the pH of an amino acid solution is lowered by adding an acid, like , the group of glutamic acid accepts the proton, acid, to form a positive ion.arrow_forward
- Draw 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_forwardGive the full name of the amino acid and based on the structure of the side chain is it hydrophobic or hydrophilic?arrow_forwardDraw the structure of the following molecule The amino acid phenylalanine at pH 1arrow_forward
- At 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_forwardAnother 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_forwardLysine and tryptophan are two amino acids that contain an additional N atom in the R group bonded to the a carbon. While lysine is classified as a basic amino acid because it contains an additional basic N atom, tryptophan is classified as a neutral amino acid. Explain why this difference in classification occurs.arrow_forward
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