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Biochemistry

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Titration Curves of Amino Acids

BIOCHM-6LH9YO

Say you were to do a comparison of two different amino acids to determine whether they could serve as an effective buffer in the lab. You take a solution of histidine and a solution of threonine and do a complete titration starting at pH = 1 and ending at pH = 14.

Structures for both amino acids are shown below in their neutral form. The pKa for the side chain of histidine is about 6.

Think about what the titration curves for each of these amino acids, and answer the following question.

How many buffering regions will be revealed by the titration curves for each of the amino acids?

Histidine and threonine shown in their neutral form. This implies nothing about their charges at any particular pH.

A

Both titration curves will show two buffering regions.

B

The titration curve for histidine will show two buffering regions while the titration curve for threonine will show three buffering regions.

C

The titration curve for threonine will show two buffering regions while the titration curve for histidine will show three buffering regions.

D

Both titration curves will show three buffering regions.