At the isoelectric point, amino acids are

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At the isoelectric point, amino acids are

At the isoelectric point, the positive and negative charges on an amino acid balance out, giving a net charge of zero. Most amino acids exist as zwitterions, with an NH3+ group and a COO− group. When pH equals the pI, these groups adjust their protonation states so that the overall charge sums to zero, so the molecule is neutral. Below this pH, the molecule tends to carry a net positive charge; above it, a net negative charge. That’s why the best description is neutral at the isoelectric point.

At the isoelectric point, the positive and negative charges on an amino acid balance out, giving a net charge of zero. Most amino acids exist as zwitterions, with an NH3+ group and a COO− group. When pH equals the pI, these groups adjust their protonation states so that the overall charge sums to zero, so the molecule is neutral. Below this pH, the molecule tends to carry a net positive charge; above it, a net negative charge. That’s why the best description is neutral at the isoelectric point.

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