15. The amino acid R is dissolved in water at pH = 7.76. Which of the following
ID: 265389 • Letter: 1
Question
15. The amino acid R is dissolved in water at pH = 7.76. Which of the following statements is true?
The amino acid will have a net charge of -1.
The amino acid will have a net charge of 0, since it is at its pI.
The amino acid will have a net charge of -2.
The amino acid will have a net charge of +2.
The amino acid will have a net charge of +1.
The amino acid will have a net charge of -1.
The amino acid will have a net charge of 0, since it is at its pI.
The amino acid will have a net charge of -2.
The amino acid will have a net charge of +2.
The amino acid will have a net charge of +1.
Explanation / Answer
Answer: Option D is correct
Explanation:
R = Arg = Arginine
pI of Arg = 11.0
pKa1 = 2.0
pKa2 = 9.0
pKa3 = 13.0
At pH = 7.76
Carboxyl group = Deprotonated
Amino group = Protonated
Side chain = Protonated
Net charge = +2
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