3) The structure of arginine, with its pKa's is shown below. Arginine has four different species

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3) The structure of arginine, with its pKa's is shown below. Arginine has four different species, which can be represented as 1) argH$_3$$^{+2}$ (shown below), 2) argH$_2$$^{+}$, 3) argH$^0$, and 4) arg$^{-1}$. a) sketch the four structures of arginine, taking care to remove the H$^+$'s in the correct order. Remember, the functional group with the lowest pKa loses its H$^+$ first. Assign charges to functional groups, where relevant. b) sketch a speciation curve for arginine; be sure to label each axis as well as the curves you generate. c) which forms (at what %) of arginine exist at a pH of 9.0 (estimate these using your speciation curve)? d) calculate the %-tage of the forms that exist at a pH of 8.5. (calculate the percentage of each species or arg and compare these to your speciation curve; does your answer make sense?) e) calculate the pH you would you need if you wanted 75% of the arginine to be in the form of argH$_3$$^{+2}$? Ignore: while these appear to be bases they do not behave this way they are exceptions to the rule.

          3) The structure of arginine, with its pKa's is shown below. Arginine has four different species, which can be represented as 1) argH$_3$$^{+2}$ (shown below), 2) argH$_2$$^{+}$, 3) argH$^0$, and 4) arg$^{-1}$.
a) sketch the four structures of arginine, taking care to remove the H$^+$'s in the correct order. Remember, the functional group with the lowest pKa loses its H$^+$ first. Assign charges to functional groups, where relevant.
b) sketch a speciation curve for arginine; be sure to label each axis as well as the curves you generate.
c) which forms (at what %) of arginine exist at a pH of 9.0 (estimate these using your speciation curve)?
d) calculate the %-tage of the forms that exist at a pH of 8.5. (calculate the percentage of each species or arg and compare these to your speciation curve; does your answer make sense?)
e) calculate the pH you would you need if you wanted 75% of the arginine to be in the form of argH$_3$$^{+2}$?
Ignore: while these appear to be bases they do not behave this way they are exceptions to the rule.

$3) The structure of arginine, with its pKa's is shown below. Arginine has four different species, which can be represented as 1) argH3^+2 (shown below), 2) argH2^+, 3) argH^0, and 4) arg^-1. a) sketch the four structures of arginine, taking care to remove the H^+'s in the correct order. Remember, the functional group with the lowest pKa loses its H^+ first. Assign charges to functional groups, where relevant. b) sketch a speciation curve for arginine; be sure to label each axis as well as the curves you generate. c) which forms (at what %) of arginine exist at a pH of 9.0 (estimate these using your speciation curve)? d) calculate the %-tage of the forms that exist at a pH of 8.5. (calculate the percentage of each species or arg and compare these to your speciation curve; does your answer make sense?) e) calculate the pH you would you need if you wanted 75% of the arginine to be in the form of argH$3$$^{+2}$? Ignore: while these appear to be bases they do not behave this way they are exceptions to the rule.$

Added by Shelia L.

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