Essential Organic Chemistry, Global Edition
3rd Edition
ISBN: 9781292089034
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Textbook Question
Chapter 17, Problem 33P
Which would have a higher percentage of negative charge at physiological pH (7.4): leucine with pI = 5.98 or asparagine with pI = 5.43?
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Aspartame has a pI of 5.9. Draw its prevailing form at physiological pH (7.4).
8. The following proteins represent a wide range of molecular weights and
isoelectric points. Mr is the molecular weight of a single protein chain.
• Protein 1: Mr 68,544; pl 6.11 (monomer)
• Protein 2: Mr 29,041; pl 5.32 (dimer)
• Protein 3: Mr 15,805; pl 5.7 (dimer)
• Protein 4: Mr 12,165; pl 4.74
a. Which protein is the most acidic? Explain your answer.
b. Which protein will migrate the slowest in an SDS-PAGE? Explain your
answer.
c. In what order will these proteins elute from a cation exchanger at pH 8?
Explain your answer.
d. In what order will these proteins salt out from a pH 7 solution by the
dropwise addition of saturated ammonium sulfate? Explain your answer.
5
83°F Cloudy
The amino acid histidine has ionizable groups with pK₁ values of 1.8, 6.0, and 9.2, as shown.
COOH
H¸Ñ—CH
CH₂ H
2
CH
pH =
COO™
H¸Ñ—CH
1.8
pk₁
CH₂ H
lonizable -COOH = -COO-
group
CH
COO™
H₂N-CH
6.0
pK₂2
CH₂ H
-HisH -His
N
CH
COO™
H₂N-CH
9.2
pk
CH₂ H
2
—NH — —NH,
CH
A biochemist makes up 95 mL of a 0.13 M solution of histidine at a pH of 5.3. She then adds 60 mL of 0.10 M HCl. What is the
pH of the resulting solution?
Chapter 17 Solutions
Essential Organic Chemistry, Global Edition
Ch. 17.1 - a. Explain why, when the imidazole ring of...Ch. 17.2 - Prob. 2PCh. 17.3 - Prob. 3PCh. 17.3 - Prob. 4PCh. 17.3 - Prob. 6PCh. 17.4 - Calculate the pI of each of the following amino...Ch. 17.4 - a. Which amino acid has the lowest pI value? b....Ch. 17.5 - What aldehyde is formed when valine is treated...Ch. 17.5 - Prob. 10PCh. 17.5 - Prob. 11P
Ch. 17.5 - Prob. 12PCh. 17.6 - Prob. 13PCh. 17.6 - What amino acid would be formed using the...Ch. 17.6 - What amino acid would be formed when the aldehyde...Ch. 17.7 - Pig liver esterase is an enzyme that catalyzes the...Ch. 17.8 - Prob. 17PCh. 17.8 - Prob. 18PCh. 17.8 - Prob. 19PCh. 17.8 - Prob. 20PCh. 17.10 - Prob. 21PCh. 17.10 - Prob. 22PCh. 17.10 - Why does cyanogen bromide not cleave on the C-side...Ch. 17.10 - Prob. 24PCh. 17.10 - Prob. 26PCh. 17.12 - Prob. 27PCh. 17.13 - a. Which would have the greatest percentage of...Ch. 17 - Draw the predominant form of the following amino...Ch. 17 - What is the pI of serine?Ch. 17 - Prob. 31PCh. 17 - Prob. 32PCh. 17 - Which would have a higher percentage of negative...Ch. 17 - Draw the form of aspartate that predominates at...Ch. 17 - Prob. 35PCh. 17 - A professor was preparing a manuscript for...Ch. 17 - a. Why is the pKa of the glutamate side chain...Ch. 17 - Prob. 38PCh. 17 - Determine the amino acid sequence of a polypeptide...Ch. 17 - Prob. 40PCh. 17 - Prob. 41PCh. 17 - Three peptides were obtained from a trypsin...Ch. 17 - Prob. 43PCh. 17 - After the polypeptide shown here was treated with...Ch. 17 - The disulfide bridges of a polypeptide were...Ch. 17 - -Amino acids can be prepared by treating an...Ch. 17 - Reaction of a polypeptide with carboxypeptidase A...Ch. 17 - Prob. 48PCh. 17 - Prob. 49PCh. 17 - Show how valine can be prepared by a. a Strecker...Ch. 17 - Prob. 51PCh. 17 - Why is proline never found in an -helix?Ch. 17 - Determine the amino acid sequence of a polypeptide...Ch. 17 - Prob. 55PCh. 17 - A chemist wanted to test his hypothesis that the...Ch. 17 - A normal polypeptide and a mutant of the...
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- 22-61 Polyglutamic acid (a polypeptide chain made only of glutamic acid residues) has an a-helix conformation below pH 6.0 and a random-coil conformation above pH 6.0. What is the reason for this conformational change?arrow_forward4a) 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.arrow_forwardNet 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].arrow_forward
- 1. If the pl for asparagine is 5.43, draw the structure at a pH of 9.5?arrow_forwardHow long is an a-helix that contains 74 amino acids? a. How long is a fully extended peptide chain that contains the same number of amino acids? (The distance between consecutive amino acids in a fully extended chain is 3.5 Å; the repeat distance of an a-helix is 5.4 Å.)arrow_forwardThis is a three-part question about a tripeptide. Answer all three sub-questions. The pKR of side chains of Tyr, and Lys is 10.46 and 10.54 respectively. The molecular weight of amino acids Ala, Lys, and Tyr in neutral form is 89.1, 146.2, and 181.2 Da, respectively. 1) Draw the chemical structure of the dominant form of tripeptide AKY at pH = 11.5, ensure you have the correct stereochemistry and ionization state of each functional group (Hint, lysine has a C-epsilon as the furthest carbon from C- alpha). 2) Calculate the pl of tripeptide AKY, assuming the terminal amino group has a pKa of 8.0, and the terminal carboxyl group has a pKa of 3.5 i^ 3) Calculate the molecular weight of AKY at pl (arrow_forward
- 11. (8) Draw the structure of the tripeptide: Asp-Cys-Lys in a solution with a pH of 6.0. What is the overall charge? Overall Charge=arrow_forwardThe amino acid histidine has ionizable groups with pK, values of 1.8, 6.0, and 9.2, as shown. COOH H₂N-CH CH, H pH = 1.29 COO H₂N-CH 1.8 CH pk, lonizable -COOH-COO- group Incorrect CH, H COO H₂N-CH 6.0 CH pk, CH, H H N CH -HisH¹-His COO H₂N-CH NH - NH, A biochemist makes up 85 mL of a 0.10 M solution of histidine at a pH of 5.5. She then adds 60 mL of 0.10 M HCI. What is the pH of the resulting solution? CH, H 9.2 C pk CH Macmillan Iraming T im be the [His IM.arrow_forwardComplete hydrolysis of a 100.00-g sample of a peptide gave the following amounts of individual amino acids (molarmasses, in g/mol, appear in parentheses):3.00 g of glycine (75.07) ;0.90 g of alanine (89.10);3.70 g of valine (117.15);6.90 g of proline (115.13);7.30 g of serine (105.10);86.00 g of arginine (174.21);(a) Why does the total mass of amino acids exceed the mass of peptide? (b) What are the relative numbers of amino acids in the peptide? (c) What is the minimum molar mass of the peptide?arrow_forward
- Consider 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_forwardConsider the formation of a dimeric protein 2P ->P2 At 25.0 °C , the enthalpy of the reaction is 17 kj/mol and the entropy of the reaction is 65 j/kmol. Is the dimerization favored at this temperature ? Thermodynamically speaking, explain/support your answer. Show work.arrow_forwardQuestion 6 of 25 > Modify lysine to show the predominant form at pH 7. Modify the amino acid by adding or removing atoms or bonds and by adding charges where appropriate. Select Draw Rings More N 0 H / || III C H-O || C ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ H H I C *一£一£一£一£ H H I N-H Erase Q2 Qarrow_forward
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