Question

Modify the structures (if necessary) to show the predominant form of the amino acid tyrosine at each pH. Be sure to include the proper number of hydrogen atoms on heteroatoms and the correct formal charges on atoms.

At pH 2.5 =

At pH 12.0 =

Answer 1

ANSWER:

Amino acids contain both -COOH and -NH_{​​​​2} groups and can exist in aqueous solution in cationic form(-NH_{​​​​3}​​^​​​+ group), Anionic form(-COO^​​​-) form or zwitterionic/dipolar form. The predominant form of an amino acid depends upon the pH of solution and on the nature of the amino acid.

At very low pH(~0) i.e., in very strongly acidic solutions, all amino acids exist primarily in cationic form, and in strongly basic solutions they are present as anions.