Why do aspartic acid and glutamic acid have a net charge of 1 at low pH and -2 – [Free] B103
Why do aspartic acid and glutamic acid have a net charge of 1 at low pH and -2 charge at high pH ? Select the single best answer. Both amino acids have two COOH groups. At low pH values, both are protonated, along with the -NH3 group. Ac high pH values, both are protonated, leading to a -2 charge overall. Both amino acids have two COOH groups. At low pH values, both are deprotonated, along with the -NH3 group. At high pH values, both are protonated, leading to a -2 charge overall. Both amino acids have two COOH groups. At low pH walues, both are protonated, along with the -NH3 group. At high pHI values, both are deprotonated, leading to a -2 charge overall. Both amino acids have two COOH groups. At low pH values, one is protonated, along with the -NH3 group. as high pH values, both are deprotonated, leading to a -2 charge overall.
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Question:
Why do aspartic acid and glutamic acid have a net charge of +1 at low pH and −2 at high pH?
Answer:
🔬 Understanding the Functional Groups
Both aspartic acid and glutamic acid contain:
- Two carboxylic acid groups (–COOH)
- One amino group (–NH₂)
🧪 Behavior at Low pH (Acidic Conditions)
- At low pH, the environment is rich in protons (H⁺).
- All acidic groups (the two –COOH) are fully protonated, and thus remain neutral.
- The amino group becomes protonated to –NH₃⁺, contributing a +1 charge.
✅ Net charge at low pH: +1
🧪 Behavior at High pH (Basic Conditions)
- At high pH, the solution lacks protons, causing deprotonation.
- Both –COOH groups lose a proton and become –COO⁻ (each contributes –1).
- The –NH₃⁺ group also loses its proton and becomes neutral –NH₂.
✅ Net charge at high pH: –2
🧾 Summary
- At low pH: 2 neutral –COOH + 1 –NH₃⁺ → +1 net charge
- At high pH: 2 –COO⁻ (–1 each) + 1 neutral –NH₂ → –2 net charge
This pH-dependent ionization explains the changes in net charge for both amino acids.