CHEM 262 ORG CHEM EBOOK DIGITAL DELIVERY
8th Edition
ISBN: 2818440043505
Author: Bruice
Publisher: PEARSON
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Chapter 21.3, Problem 6P
Interpretation Introduction
Interpretation:
Reason for the carboxylic group of the amino acid is more acidic than a
Concept Introduction:
Acid-base properties of Amino acids:
Every amino acid has a carbonyl group and an amino group, and each group can exist in an acidic form or a basic form, depending on
The compound exists primarily in the acidic form in solutions that are more acidic than their
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Why are the carboxylic acid groups of the amino acids more acidic (pKa - 2) than a carboxylic acid such as acetic acid (pKa = 4.76)?
4a) Canavanine is an amino acid that is produced by some legume plants. It is not used in proteins but serves as a nitrogen storage molecule in seeds, and is being investigated as a possible anti-cancer and anti-viral drug. Canavanine's amino and carboxyl groups are the same as those in any other amino acid (pKa for the amino group is 8.0 and pKa for the carboxyl group is 3.1), and its side group has a single ionizable group with a pKa of 7.0. Describe or explain what that statement (the previous sentence) tells you about the protonation state of each of the 3 ionizable groups on this amino acid if it is dissolved in pure distilled water at pH 7.0.
Net Charge on an Amino Group.The amino acid glycine has hydrogen as its side-chain (R) group. Values of pKca= 2:36 and pKaa=9:56 have been previously reported for glycine. Superscripts c, a, and s refer to a-carboxylic acid, α-amino base, and side chain, respectively. Using these values, determine the net charge on the a-amino group of glycine at a physiologic pH of 7.2 and a pH of 3 [70].
Chapter 21 Solutions
CHEM 262 ORG CHEM EBOOK DIGITAL DELIVERY
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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- 22-59 What is the effect of salt bridges on the tertiary structure of proteins?arrow_forwardIn 0.1M solution glycine (pKa 9.6) at pH of 9.0, what fraction of glycine has its amino group in the -NH3+ form?arrow_forwardComplete the table for the ionizable groups of the fictitious amino acid hypothetinine. pka (to TWO decimals) Average charge of group when pH=pK (to ONE decimal) Group Ka alpha-carboxyl 1.38 x 103 alpha-amino 6.02 x 10-10arrow_forward
- (Q25) A buffer solution is prepared by adding 0.780 moles of formic acid and 0.760 moles of sodium formate. What will the solution pH be if 0.272 moles of sodium hydroxide (NaOH) is added to the buffer solution? The Ką of formic acid is 1.8 x 104.arrow_forwardA naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. a. If the pKa value of a carboxylic acid such as acetic acid is about 5 (see Table 2.1), then why is the pKa value of the carboxylic acid group of alanine so much lower? b. Draw the structure of alanine in a solution at pH = 0. c. Draw the structure of alanine in a solution at physiological pH (pH 7.4). d. Draw the structure of alanine in a solution at pH = 12. e. Is there a pH at which alanine is uncharged (that is, neither group has a charge)? f. At what pH does alanine have no net charge (that is, the amount of negative charge is the same as the amount of positive charge)?arrow_forwardCalculate the pKa of each acid and indicate which is the stronger acid. C6O2H8, Ka = 1.7 x 10–5 C2O4H2, Ka = 5.9 x 10–2arrow_forward
- 2. Classify the following amino acids as nonpolar, polar basic, polar acidic, or polar neutral. (a) (b) (c) (d) H₂N-CH-COH CH-OH I CH3 || H₂N-CH-C-OH I CH₂ C=O 1 OH H₂N-CH-C-OH CH₂ T CH-CH3 CH₂ H₂N-CH-C-OH ī CH₂ OH 229arrow_forwardYou are given the structures of the amino acids alanine (Ala), methionine (Met) and threonine (Thr). to H2N CO2H H2N CO2H H2N co,Harrow_forwardGlutamic acid has three ionizable groups. The pKa of α-COOH is 2.19; α-NH 3 + , 9.67; and the R-group, 4.25. What is the predominant charge of glutamic acid at pH 10.00?arrow_forward
- Pentapeptide has a sequence GRIND -Draw the pentapeptide in its proper ionization state at pH 7.0 -What is the pI of the pentapeptidearrow_forwardAll amino acids share a common structure, a central (alpha) carbon with four groups attached. Which of these is NOT one of the four groups attached to the alpha- carbon? O an R group an ammonium group (-NH3+) O a carboxylate group (-COO) a hydronium grouparrow_forwardSee Appendix on p5 for list of amino acids. Aspartame is a sweetener. The structure of aspartame, along with the titration curve showing its pKal and pka2 is given below. 14 € 12 10 8 6 4 2 0 pK₂2 = 7.87 PK₁₁ = 3.19 0 0.5 1 Equivalents of NaOH a) Copy the structure of aspartame. i) 1.5 2 OH S NH₂ Aspartame LOCH 3 Identify the two ionisable groups. Re-draw the groups in their protonated forms, and label each with their pka. ii) Circle and identify the two amino acids in aspartame.arrow_forward
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