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How does the charge of glycine change in acidic and alkaline solutions?
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Amino acid
The structure and function of amino acids.
In aqueous solutions, amino acids like glycine exist as dipolar ions, or zwitterions, which carry both positive and negative charges. Because they are amphoteric, they can react with acids or bases to neutralize these charges, allowing them to act as buffers.12
The charge of glycine changes depending on the pH of the solution:
- In acidic solutions: Glycine carries a net positive charge. Consequently, it migrates toward the cathode (the negative electrode) in an electrical field.1
- In alkaline solutions: The charge of glycine becomes negative, causing it to migrate toward the anode (the positive electrode).1
At a pH of 6.1, known as the isoelectric point, glycine carries an equal number of positive and negative charges, resulting in a net zero charge; at this point, the molecule does not migrate in an electrical field.1