The amino acid glycine is often used as an ingredient in buffers for biochemistry experiments. The amino group of glycine has a pKa of 9.6. Glycine exists in either a protonated form (-NH3*) or a free base (-NH₂). a) In what pH range can glycine be used as an effective buffer? b) In a 0.1M solution of glycine at pH 9.0, what fraction has its amino group in the protonated form? c) When 99% of the glycine is in the protonated from, what is the numerical relation between the pH of the solution and the pKa of the amino group?
The amino acid glycine is often used as an ingredient in buffers for biochemistry experiments. The amino group of glycine has a pKa of 9.6. Glycine exists in either a protonated form (-NH3*) or a free base (-NH₂). a) In what pH range can glycine be used as an effective buffer? b) In a 0.1M solution of glycine at pH 9.0, what fraction has its amino group in the protonated form? c) When 99% of the glycine is in the protonated from, what is the numerical relation between the pH of the solution and the pKa of the amino group?
Biochemistry
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Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
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Chapter1: Biochemistry: An Evolving Science
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Transcribed Image Text:The amino acid glycine is often used as an ingredient in buffers for biochemistry
experiments. The amino group of glycine has a pKa of 9.6. Glycine exists in either a
protonated form (-NH3+) or a free base (-NH₂).
a) In what pH range can glycine be used as an effective buffer?
b) In a 0.1M solution of glycine at pH 9.0, what fraction has its amino group in the
protonated form?
c)
When 99% of the glycine is in the protonated from, what is the numerical relation
between the pH of the solution and the pKa of the amino group?
Expert Solution
Step 1
Proteins are composed of twenty naturally occurring amino acids. The amino acids have ionizable groups that can be in their protonated or deprotonated state. The state of protonation of the alpha-amino, alpha-carboxyl and the side chain of amino acids depends upon the pKa of the functional group and the pH of the surrounding medium.
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