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1. You need 0.5 liter of a 0.1 M buffer for a biochemical reaction that you plan to perform at pH 2.0. On the shelf in your laboratory you have available phosphoric acid, and the amino acids aspartate, glycine, glutamate, tyrosine, and histidine (all you have available are the fully deprotonated forms of the molecules); these are the only buffer materials you have available. (The pKå values for these compounds are given below.) For phosphoric acid, pKa1 = 2.12, pKa2 = 7.21, and pKa3 = 12.32 For aspartate, pKaCOOH = 1.88, pKaNH3+ = 9.60, pKa sidechain = 3.65 For glycine, pKaCOOH = 2.34, pKaNH3+ = 9.60 For glutamate, pKaCOOH = 2.19, pKaNH3+ = 9.67, pKa sidechain = 4.25 For histidine, pKaCOOH = 1.82, pKaNH3+ = 9.1 pKa sidechain = 6.00 For tyrosine, pKɑCOOH = 2.20, pKɑNH3+ = 9.11, pKa sidechain 10.07 a. Of these possible buffers, which is likely to yield the greatest resistance to pH change from the starting pH of 2.0, assuming that you were going to run a biochemical reaction that absorbed 0.003 moles of protons from 0.5 L of your buffer? (I recommend performing the calculations and showing a table of the pH change for reasonable candidate buffer species.) b. Of these possible buffers, which is likely to yield the greatest resistance to pH change from the starting pH of 2.0, assuming that you were going to run a biochemical reaction that released 0.003 moles of protons into 0.5 L of your buffer? (I recommend performing the calculations and showing a table of the pH change for reasonable candidate buffer species.) c. How many moles of NaOH or HCl would you have to add to make 0.5 liter of a 0.1 M buffer (pH 2.0) using the most effective of the possible buffer molecules? (If there is more than one "most effective" please perform the calculations for each of the better choices.)

1. You need 0.5 liter of a 0.1 M buffer for a biochemical reaction that you plan to perform at pH 2.0. On the shelf in your laboratory you have available phosphoric acid, and the amino acids aspartate, glycine, glutamate, tyrosine, and histidine (all you have available are the fully deprotonated forms of the molecules); these are the only buffer materials you have available. (The pKå values for these compounds are given below.) For phosphoric acid, pKa1 = 2.12, pKa2 = 7.21, and pKa3 = 12.32 For aspartate, pKaCOOH = 1.88, pKaNH3+ = 9.60, pKa sidechain = 3.65 For glycine, pKaCOOH = 2.34, pKaNH3+ = 9.60 For glutamate, pKaCOOH = 2.19, pKaNH3+ = 9.67, pKa sidechain = 4.25 For histidine, pKaCOOH = 1.82, pKaNH3+ = 9.1 pKa sidechain = 6.00 For tyrosine, pKɑCOOH = 2.20, pKɑNH3+ = 9.11, pKa sidechain 10.07 a. Of these possible buffers, which is likely to yield the greatest resistance to pH change from the starting pH of 2.0, assuming that you were going to run a biochemical reaction that absorbed 0.003 moles of protons from 0.5 L of your buffer? (I recommend performing the calculations and showing a table of the pH change for reasonable candidate buffer species.) b. Of these possible buffers, which is likely to yield the greatest resistance to pH change from the starting pH of 2.0, assuming that you were going to run a biochemical reaction that released 0.003 moles of protons into 0.5 L of your buffer? (I recommend performing the calculations and showing a table of the pH change for reasonable candidate buffer species.) c. How many moles of NaOH or HCl would you have to add to make 0.5 liter of a 0.1 M buffer (pH 2.0) using the most effective of the possible buffer molecules? (If there is more than one "most effective" please perform the calculations for each of the better choices.)

Biochemistry
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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### Laboratory Buffer Preparation for Biochemical Reactions You are tasked with preparing a 0.5-liter solution of a 0.1 M buffer for a biochemical reaction at pH 2.0. Available materials in your laboratory include phosphoric acid and the amino acids aspartate, glycine, glutamate, tyrosine, and histidine, all in their fully deprotonated forms. The \( pK_a \) values for these compounds are provided below. #### \( pK_a \) Values: - **Phosphoric acid** - \( pK_{a1} = 2.12 \) - \( pK_{a2} = 7.21 \) - \( pK_{a3} = 12.32 \) - **Aspartate** - \( pK_{a \text{COOH}} = 1.88 \) - \( pK_{a \text{NH}_3^+} = 9.60 \) - \( pK_{a \text{sidechain}} = 3.65 \) - **Glycine** - \( pK_{a \text{COOH}} = 2.34 \) - \( pK_{a \text{NH}_3^+} = 9.60 \) - **Glutamate** - \( pK_{a \text{COOH}} = 2.19 \) - \( pK_{a \text{NH}_3^+} = 9.67 \) - \( pK_{a \text{sidechain}} = 4.25 \) - **Histidine** - \( pK_{a \text{COOH}} = 1.82 \) - \( pK_{a \text{NH}_3^+} = 9.17 \) - \( pK_{a \text{sidechain}} = 6.00 \) - **Tyrosine** - \( pK_{a \text{COOH}} = 2.20 \) - \( pK_{a \text{NH}_3^+} = 9.11 \) - \( pK_{a \text{sidechain}} = 10.07 \) #### Questions for Analysis: a. **Buffer Resistance to pH Change
Transcribed Image Text:### Laboratory Buffer Preparation for Biochemical Reactions You are tasked with preparing a 0.5-liter solution of a 0.1 M buffer for a biochemical reaction at pH 2.0. Available materials in your laboratory include phosphoric acid and the amino acids aspartate, glycine, glutamate, tyrosine, and histidine, all in their fully deprotonated forms. The \( pK_a \) values for these compounds are provided below. #### \( pK_a \) Values: - **Phosphoric acid** - \( pK_{a1} = 2.12 \) - \( pK_{a2} = 7.21 \) - \( pK_{a3} = 12.32 \) - **Aspartate** - \( pK_{a \text{COOH}} = 1.88 \) - \( pK_{a \text{NH}_3^+} = 9.60 \) - \( pK_{a \text{sidechain}} = 3.65 \) - **Glycine** - \( pK_{a \text{COOH}} = 2.34 \) - \( pK_{a \text{NH}_3^+} = 9.60 \) - **Glutamate** - \( pK_{a \text{COOH}} = 2.19 \) - \( pK_{a \text{NH}_3^+} = 9.67 \) - \( pK_{a \text{sidechain}} = 4.25 \) - **Histidine** - \( pK_{a \text{COOH}} = 1.82 \) - \( pK_{a \text{NH}_3^+} = 9.17 \) - \( pK_{a \text{sidechain}} = 6.00 \) - **Tyrosine** - \( pK_{a \text{COOH}} = 2.20 \) - \( pK_{a \text{NH}_3^+} = 9.11 \) - \( pK_{a \text{sidechain}} = 10.07 \) #### Questions for Analysis: a. **Buffer Resistance to pH Change
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