How does the structure of serine change as it goes from an acidic to a basic medium?
Serine exists as a zwitterion.
In very acidic solutions (pH 1), the COO⁻ group will be protonated
COOH = 2.2
NH₃⁺ = 9.2
As you make the solution more basic, you will remove the acidic protons one by one.
By the time you reach pH 12, you will have removed all of the acidic protons.
Serine will exist as NH₂CH(CH₂OH)COO⁻.