Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 2, Problem 18P
Histidine is an amino acid with three titratable groups: an -NH3+ group (pKa = 9.2) —COOH group (pKa = 1.8). and an imidazole (
a. Identify which point on the titration curve corresponds to the pKa for each of the titratable groups, and which point corresponds to the pl. Explain your choices.
b. Calculate the value of pl for histidine.
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E. Histidine is an amino acid with three titratable groups: an -NH," group
(pK, = 9.2), a -COOH group (pK, = 1.8), and an imidazole (amine-
like) group (pK, = 6.0). The titration curve for histidine is shown below
with four points highlighted.
(a) Identify which point on the titration curve corresponds to the pK, for
each of the titratable groups, and which point corresponds to the pl.
Explain your choices.
(b) Calculate the value of pl for histidine.
14
12
10
6.
4
2-
2
3
Moles "OH added per mole histidine
на
Sketch the titration curve for the amino acid alanine with pka1 = 2.34 and pka2 = 9.69.
LEFT:You have the following titration curve of an amino acid with a non-polar R-group with
arrows on curve from (1) to (5).
RIGHT: This amino acid has the following structures (a) to (e)) at different points of the
titration curve. Match each numbered arrow on the curve (from (1) to (5)) with the appropriate
amino acid structure (from (a) to (e))
12
(5)
H.NCHCOH + HNCHCO
(a)
10
(4)
CH3
CH
Isoelectrin
HŃCHCO +
(b)
ppint
43)
HNCHCO
CH3
CH3
(2)
HaNCHCOH
H. NCHCO (e)
(d
CH3
CH3
0.0
0.5
1.0
15
20
NaOH equivalents.
H-NCHCO
(e)
CH3
Chapter 2 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
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 - A biochemical reaction takes place in a 1.00 ml...Ch. 2 - Is RNA-binding enzyme RNase A more likely to have...Ch. 2 - Consider a protein in which a negatively charged...Ch. 2 - Prob. 23PCh. 2 - Prob. 24P
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biochemistry and related others by exploring similar questions and additional content below.Similar questions
- LEFT You have the following titration curve of an amino acid with a non-polar R-group with arrows on curve from (1) to (5). RIGHT. This amino acid has the following structures ((a) to (e)) at different points of the titration curve. Match each numbered arrow on the curve (from (1) to (5) with the appropriate amino acid structure (from (a) to (e)) 12 (5) H,NCHCOH + H NCHC (a) 10 (4) CH, CH Isoelectrie HNCHCO+ (b) point HNCHCO 43) CH CH (2) HNCHCOH H,NCHCO (C) CH3 CH3 0.0 0.5 1.5 20 NaOH equivalents HNCHCO (e) CH3arrow_forwardWrite a structural formula for a tetrapeptide composed of phenyl-alanine, glycine, aspartic acid, and histidine in which the phenylalanine is N-terminal and the histidine is C-terminal. How many different tetrapeptides could be written that fit the criteria in this question?arrow_forwardDraw the titration curves for the following AA’s: Aspartic acid, Alanine, Lysine, Valine, Serine, and Trrosine.arrow_forward
- 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?arrow_forwardHemoglobin is considered to be a tetrameric complex with a 64 kDa (α β)2. When attempting to purify hemoglobin, we must first purify the α and β monomers (about 16 kDa each) to prepare the tetramer. This is formed from the dimer intermediate: 2 α + 2 β -> 2 αβ -> (α β)2. 1. The graph given represents a size-exclusion chromatogram after the refolding of the hemoglobin tetramer. This process is not 100% efficient, so we may have leftovers of dimers and monomers. In the graph given, can we label the peaks given as a tetramer, dimer, or monomer?arrow_forwardThe melanocyte-stimulating peptide hormone a-melanotropin has the following sequence: Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val (a) Write the sequence using the one-letter abbreviations. (b) Calculate the molecular weight of a-melanotropin, a da'arrow_forward
- Consider the peptide Lys-Ser-Glu-Cys-His-Tyr. For the drawings requested below,please show in zig-zag style, from amino to carboxy terminus, with correctstereochemistrya. Draw the predominant form at pH = 2b. Draw the predominant form at pH = 5c. Draw the predominant form at pH = 7d. Draw the predominant form at pH = 12arrow_forwardFor the dipeptide Arg–His, find the pI (the pKs are α-amino 9.0, guanidino 12.5, imidazole 6.0, α-carboxylate 2.1).arrow_forwardPolylysine adopts a random structure in solution at physiological pH (i.e. 7.4). Given that the e-amino group of lysine has a pKa of 10.5, under what circumstances do you think polylysine will form an a-helix? Give an explanation for your decision. Given the pKa of the side-chain COOH group, under what circumstances would you anticipate polyglutamate to form an a-helix?arrow_forward
- Asp-Gly-Lys-Glu-Ile-Phe Draw its full chemical structure as it would exist at pH = 7.0. Draw an arrow pointing to each peptide bond. Identify the net charge of the peptide and briefly explain how you arrived at this answer.arrow_forwardnumber 5-21arrow_forwardExplain why the indole nitrogen of tryptophan is more weakly basic than one of the imidazole nitrogens of histidine What is the relationship between (R)-cysteine and (S)-alanine Do they have the opposite three-dimensional configuration (as the names might suggest) or the same configuration? Is (R)-cysteine a D-amino acid or an L-amino acid?arrow_forward
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