What percentage of the lysine side chain amino group is de-protonated at pH7?(pKa lysine side chain amino group = 10.5)
Question
What percentage of the lysine side chain amino group is de-protonated at pH7?(pKa lysine side chain amino group = 10.5)
Solution
To answer this question, we need to use the Henderson-Hasselbalch equation, which is:
pH = pKa + log([A-]/[HA])
Where:
- pH is the pH of the solution
- pKa is the acid dissociation constant
- [A-] is the concentration of the base (deprotonated form)
- [HA] is the concentration of the acid (protonated form)
We are asked to find the percentage of the lysine side chain amino group that is deprotonated at pH 7. This is equivalent to finding the ratio [A-]/([A-] + [HA]).
First, we rearrange the Henderson-Hasselbalch equation to solve for [A-]/[HA]:
[A-]/[HA] = 10^(pH - pKa)
Substitute the given values:
[A-]/[HA] = 10^(7 - 10.5) = 10^(-3.5)
Now, we can find the percentage of the lysine side chain amino group that is deprotonated:
% deprotonated = [A-]/([A-] + [HA]) * 100%
Assuming that [A-] + [HA] = 1 (because the sum of the protonated and deprotonated forms equals the total), the equation simplifies to:
% deprotonated = [A-] * 100%
Substitute the value of [A-]/[HA] into the equation:
% deprotonated = 10^(-3.5) * 100% ≈ 0.03%
So, at pH 7, approximately 0.03% of the lysine side chain amino group is deprotonated.
Similar Questions
What is the net charge on the amino acid lysine at pH = 7.4 if pKa1 = 2.16, pKa2 = 9.06, and the pKa of the side chain = 10.54?A.+1B.+2C.0D.-1
A new amino acid with a basic side chain has been identified with the following pka values:pKa (-COOH) = 2.10pKa (-NH3+) = 9.44pKa (basic side chain) = 10.51What is the charge at pH = 1.50? (you don't have to include the "+" for positive charges but you do need to include the "-" for negative charges)
A new amino acid with an acidic side chain has been identified with the following pka values:pKa (-COOH) = 2.09pKa (-NH3+) = 9.82pKa (acidic side chain) = 3.85What is the pI?
At pH 7, approximately what charge would be on your peptide? Explain your answer. (2 marks)
Based on the pKa of the histidine side chain given in the passage, which of the following best describes the charges of the His-His dipeptide side chains at pH 7?A.The side chains all have a charge of 0.B.The side chains all have a charge of +1.C.Most of the side chains have a charge of 0, but a small percentage have a positive charge.D.Most of the side chains have a charge of +1, but a small percentage are neutral.
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.