aAll amino acids have at least two ionizable groups: an a-amino group (average pK₁ of 8.0) andan α-carboxylic acid group (average pK₂ of 3.1). Histidine also has an ionizable side chain (Rgroup) with a pKa of about 6.0. One of the possible ionization states of histidine is shown inathe image.Select the pH values at which the charged form of the R group would predominate.6.0At what pH would the structure shown be the predominant ionization state? Consider the ionization state of all three of thefunctional groups.2.2+The protonated form of the R group of histidine is shown in the structure. The ratio of the charged (protonated) form to thedeprotonated form depends on the pK₁ of the R group and the pH of the solution.4.9H₂N-CH-C-OH|CH₂11.5+HN-NH

pKa is the pH at which a weak acid is 50% dissociated into a proton and conjugate base.At pH <…

Answered: All amino acids have at least two…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Amino acid Cys has ionizable groups with pKa values 2.0, 8.0, and 10.0. Determine the charge on the Cys at the following pH. Be sure to write the charge in fraction with sign in front (for example, +1/2, -1/5, and +7/8). Charge when pH is at 1.0? _________ Charge when pH is at 9.0? _________ Charge when pH is at 8.0? _________ Charge when pH is at 10.0? _________
Place each charge form of alanine under the pH condition where it would be the predominant form. The pK₁ values for the carboxyl group and amino group of alanine are approximately 2.3 and 9.7, respectively. pH 11 H | H₂C-C-COO NH₂ Does not occur in significant amounts at any pH
Determine the net charge (to the nearest integer) on the following peptide at pH 5 AND pH 12. Estimate the isoelectric point (pl) for this peptide: H2N-Leu-Gly-Lys-Glu-COOH Assume the pK,s for functional groups are: alpha-amino 6. alpha-carboxy sidechain-amino (Lys) 10.5 sidechain-carboxy (Glu) 4.2 O Net charge at pH 5 and 12 is 0 and -2, respectively, pl =6.6 O Net charge at pH 5 and 12 is 0 and -2, respectively, pl =3.1 O Net charge at plH 5 and 12 is +2 and -1, respectively, pl =7.5 O Nct charge at pH 5 and 12 is +1 and -1. respectively,. pl -4.5 2.
Each ionizable group of an amino acid can exist in one of two states, charged or neutral. The electric charge on the functional group is determined by the relationship between its pKa and the pH of the solution. This relationship is described by the Henderson-Hasselbalch equation. a Histidine has three ionizable functional groups. Complete the equilibrium equations by assigning the proper pK₁ for each ionization and the net charge on the histidine molecule in each ionization state. H || H₂N-C-C-OH | CH₂ 2 + HN -1 -NH pKa = 1.8 +2 || H₂N-C-C-0- 1 CH₂ + HN -NH pKa = 9.17 Answer Bank pK₂ = 7.59 H|| H₂N-C-C-0- | CH₂ N pKa -NH = 6.0 -2 н II H₂N-C-C-0- | CH₂ +1 N C -NH 0
A 100 ml solution of 0.1 M amino acid (AA) at ph 1.0 was titrated with NaOH solution. The pH was monitored, and the results were plotted on the graph. The keypoints in the titration are designated I to VII. What is the possible identity of the amino acid? What is the isoelectric point of AA? what is the pKa corresponding to the dissociation of the alpha carboxylic group? Region/point where AA is predominantly present as a (-1) charged species? The effective buffering range for the amino acid in the acidic region? Region/point where the solution has 50:50 percent mixture of the (0) and (-1) species
Amino acid structure For any ionizable group, indicate the pka value and draw the structure that would be expected at the pH inside the cell (~7.4).
The peptide aspartyl-glutamyl-leucyl-threonyl-alanine, shown in the sketch drawing window, has several ionizable groups. Adjust the charges to show the molecule as it would exist at pH 5.00. Use the pk values in the table below. pK, Values for Ionizable Groups of Amino Acids. Amino Acid pA, of a-COOH pA, of e-NH, pA, of Side Chain Isoelectric Point (pI) Alanine 235 9.87 6.11 Arginine 2.01 9.04 12.48 10.76 Asparagine 2.02 8.80 5.41 Aspartic acid 210 9.82 3.86 298 Cysteine 2.05 10.25 8.00 5.02 Glutzmic acid 2.10 9.47 4.07 3.08 Glutamine 217 9.13 5.65 Glycine 235 9.78 6.06 Histidine 7.11 9.18 6.10 7.64 Isoleucine 232 9.76 6.04 Leucine 233 9.74 6.04 Lysine 218 8.95 10.53 9.74 Methionine 2 28 9.21 5.74 Phenylalanine 2 58 9.24 5.91 Proline 2.00 10.60 6.30 Serine 221 9.15 5.68 Threonine 2.09 9.10 5.60 Trуptophan 238 9.39 5.88 Tyrosine 2 20 9.11 10.07 5.63 Valine 2 29 9.72 6.00 • Use the wedge hash bond tools to indicate stereochemistry where it exists. • If a group is 2chiral, do not use…
The pK, of the α-carboxyl group of serine is 2.21, and the pK, of its α-amino group is 9.15. Calculate the average net charge on serine if it is in a solution that has a pH of 9.00. average net charge on serine:
You are given 0.5 M solution of the amino acid Arginine. pK1 (α-carboxyl group) = 2.17 pK2 (α- amino group) = 9.03 and pK3 (guanidine group) = 12.48 Determine the pH of the solution if you add 15 mL 0.25 M HCl to 10 mL of the 0.5 M Arginine. Assume that Arginine is in isotonic state. Show all calculations
Each ionizable group of an amino acid can exist in one of two states, charged or neutral. The electric charge on the functional group is determined by the relationship between its pKa and the pH of the solution. This relationship is described by the Henderson-Hasselbalch equation.(a) Histidine has three ionizable functional groups. Write the equilibrium equations for its three ionizations and assign the proper pKafor each ionization. Draw the structure of histidine in each ionization state. What is the net charge on the histidine molecule in each ionization state?(b) Draw the structures of the predominant ionization state of histidine at pH 1, 4, 8, and 12. Note that the ionization state can be approximated by treating each ionizable group independently.(c) What is the net charge of histidine at pH 1, 4, 8, and 12? For each pH, will histidine migrate toward the anode (+) or cathode (−) when placed in an electric field?
Given the following Peptide: Q6 *H;N-Phe-Asp-Ala-Arg-Gy-His-Arg-Asp-Glu-His-Tyr-CO 6a. What is the peptide's net charge at pH 2.0, pH 6.0, pH 7.4, and pH 10.2? (show work) 6b. What is the approximate isoelectric point of this peptide?
Draw the Ala-Ser-Leu-Asp polypeptide (perspective formula) showing the fully extended backbone geometry (all angles +/- 180°). Include correct stereochemistry for L-amino acids. Label all bond rotations representing the angles at each residue

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