BIOCHEMISTRY BOOKS ALC&MOD MST/ET PKG
1st Edition
ISBN: 9780134172507
Author: APPLING
Publisher: Pearson Education
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Chapter 2, Problem 15P
The anno acid arginine ionizes according to the following scheme:
a. Calculate the isoelectric point of arginine. You can neglect contributions from form l. Why?
b. Calculate the average charge on arginine when pH = 9.20. (Hint: Find the average charge for each ionizable group and sum these together)
c. Is the value of average charge you calculated in part b reasonable, given the pl you calculated part a? Explain your answer.
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The amino acid arginine ionizes according to the following scheme: (a) Calculate the isoelectric point of arginine. You can neglect contributions from form I. Why? (b) Calculate the average charge on arginine when pH = 9.20. (c) Is the value of average charge you calculated in part b reasonable, given the pI you calculated in part a? Explain your answer
Protein A is made up of a single polypeptide chain; The molecular mass of A is 20,000 Da; the A molecule has 2 tryptophan residues, 5 tyrosine residues, and no disulfide bonds. Calculate what absorbance (at 280 nm) a solution of protein A will have at a concentration of 1.0 mg / mL, in a 1 cm cell. Write the calculations you have done.
For the following pentapeptides: Ser-Glu-Gly-His-Ala and Gly-His-Ala-Glu-Ser
A. Compute their isoelectric pH (pI). Show full solution. Use standard pKa values.
B. Do these peptides with the same amino acid composition have different net charges at pH 7.0? Explain briefly.
C. Would you expect the titration curves of the two peptides to differ? Why or Why not?
Chapter 2 Solutions
BIOCHEMISTRY BOOKS ALC&MOD MST/ET PKG
Ch. 2 - Suppose a chloride ion and a sodium ion are...Ch. 2 - Draw two different possible hydrogen-bonding...Ch. 2 - Prob. 3PCh. 2 - 4. What is the pH of each of the following...Ch. 2 - Prob. 5PCh. 2 - The weak acid HA is 2% ionized (dissociated) in a...Ch. 2 - 7. Calculate the pH values and draw the titration...Ch. 2 - What is the pH of the following buffer mixtures?...Ch. 2 - a. Suppose you wanted to make a buffer of exactly...Ch. 2 - Prob. 10P
Ch. 2 - You need to make a buffer whose pH is 7.0, and you...Ch. 2 - Describe the preparation of 2.00 L of 100 glycine...Ch. 2 - Carbon dioxide is dissolved in blood (pH 7.4) to...Ch. 2 - What is the molecular basis for the observation...Ch. 2 - The anno acid arginine ionizes according to the...Ch. 2 - It is possible to make a buffer that functions...Ch. 2 - A student is carrying out a biological preparation...Ch. 2 - Histidine is an amino acid with three titratable...Ch. 2 - Prob. 19PCh. 2 - Prob. 20PCh. 2 - Prob. 21P
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- 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?arrow_forwardAt a pH equal to the isoelectric point of alanine, the net charge on alanine is zero. Two structures can be drawn that have a net charge of zero, but the predominant form of alanine at its pI is zwitterionic.(a) Why is alanine predominantly zwitterionic rather than completely uncharged at its pI?(b) What fraction of alanine is in the completely uncharged form at its pI? Justify your assumptions.arrow_forward1) (10 points) Draw a schematic of the chemical structure of the Leu-Tyr-Met-Lys tetrapeptide, with the correct ionization at neutral pH (pH 7). Also, give an estimate the pl of this tetrapeptide (you are given that the pKa of any acidic R group is 4, the pKa of any basic R group is 11.5, and the pKa of the a-COOH is 2, and the a-NH3 is 9.5). Provide rationale!arrow_forward
- 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) speciesarrow_forwardDetermine the net charge on the following pentapeptide "Lys-Ala-His-Asp-Ser" at: a. pH 1.0 b. pH 10.1arrow_forwardYou 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 b. Draw the structure of the amino acid at the pH determined in question 1arrow_forward
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