(4 pts) Circle the best answer. Which of the following sequences corresponds to
ID: 192309 • Letter: #
Question
(4 pts) Circle the best answer. Which of the following sequences corresponds to an alpha helix with one hydrophobic face and one hydrophilic face? (Hint: you can use the helical wheel diagram on the right to help in your analysis.) 20. a. Ala-Ala-Ala-Ala-Ala-Ala-Val-Val-Val-Val-Va b. Ser-Val-Ser-Val-Ser-Val-Ser-Val-Ser-Val-Ser C. Asp-Val-Val-His-Val-Val-Asp-Asp-Val-Val-Asp 9 8 6 (8 pts) 100 mL of a solution of 0.1 M glycine at pH 1.72 was titrated with 2 M NaOH solution. The pH was monitored, and the results were plotted as shown in the graph below. 21. 12 1130 109.60 .97. 234 0.5 1.0 1.5 2.0 OH (equivalents) a. What is the pKa of the amino group? b. At what pH is glycine present as a 50:50 mixture of "H3N-CH2-COOH and "H3N-CH2-COO? c. What are the two pH ranges in which glycine is a good buffer? From to- and from to Hint: Read the questions carefully! You are being asked for pH values, not the numbered points on the graph (I, II, Ill, etc.) Your answers to part c should be based on an understanding of buffering range; you won't find the values already printed in the figure.Explanation / Answer
20:The answer is c.
21 a- pka of amino group is 9.6
b-pH=5.97
c- Glycine is good buffer in the range of 2.2 -3.6 and also between 8.8 - 10.6
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