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.

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.

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter27: Amino Acids And Proteins

Section: Chapter Questions

Problem 27.39P: A chemically modified guanidino group is present in cimetidine (Tagamet), a widely prescribed drug...

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A chemically modified guanidino group is present in cimetidine (Tagamet), a widely prescribed drug for the control of gastric acidity and peptic ulcers. Cimetidine reduces gastric acid secretion by inhibiting the interaction of histamine with gastric H2 receptors. In the development of this drug, a cyano group was added to the substituted guanidino group to alter its basicity. Do you expect this modified guanidino group to be more basic or less basic than the guanidino group of arginine? Explain.
Explain why the pI of lysine is the average of the pKa values of its two protonated amino groups.
For lysine and arginine, the isoelectric point, pI, occurs at a pH where the net charge on the nitrogen-containing groups is +1 and balances the charge of -1 on the a-carboxyl group. Calculate pI for these amino acids.
(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?
If the pH of a solution of Arginine is equal to a half of the 3 pka values of all of its functional groups, what will be the charge on the majority of the Arg molecules in that solution? Please explain. Am i supposedd to add up the three pka values and then divide it in half to find the pH? Thanks
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 residues
The amino acid (S)-alanine has the physical characteristics listed under the structure. How does the melting point of a racemic mixture of (R)- and (S)-alanine compare to the melting point of (S)-alanine?
Glutamic acid is a naturally occurring α-amino acid that contains acarboxy group in its R group side chain. (Glutamic acid isdrawn in its neutral form with no charged atoms, a form that does not actually exist at any pH.) a.) What form of glutamic acid exists at pH = 1?b.) If the pH is gradually increased, what form of glutamic acid exists afterone equivalent of base is added? After two equivalents? After threeequivalents?c.) Propose a structure of monosodium glutamate, the common flavorenhancer known as MSG.
a) A solution of amino acid having carboxylic side chain was titrated against NaOH. If initial pH of the solution was 2.8. Describe the state of the functional groups of the amino acid at the initial pH and at 10.5.b) Briefly explain how you will separate amino acids mixture using the charge difference between the amino acids. c) A 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.
The pKa values for the amino and carboxyl groups of alanine are 9.69 and 2.35, respectively. Calculate the pH of 10 mL of 50 mM alanine buffer (pH 10) following the addition of: a. 0.1 mL of 1.5 M HCl b. 0.3 mL of 1.5 M HCl
For the amino acid alanine, the major species in solution at pH 7 is the zwitterionic form, which has a negatively charged carboxylic acid group and a positively charged amino group. There is a less common neutral form in which neither group is charged. The carboxylic acid group of alanine has a p?a of 3 The amino group of alanine has a p?a of 8 Estimate the ratio of the concentration of the neutral amino acid species to the zwitterionic species at pH 7. __?__x10^?
For the amino acid alanine, the major species in solution at pH 7 is the zwitterionic form, which has a negatively charged carboxylic acid group and a positively charged amino group. There is a less common neutral form in which neither group is charged. The carboxylic acid group of alanine has a p?apKa of 3.3. The amino group of alanine has a p?apKa of 8.8. Estimate the ratio of the concentration of the neutral amino acid species to the zwitterionic species at pH 7.