Question

if one peptide's pH is 7, it's net charge is 0?

Answer 1

No

pH value of 7 means that the solution is neutral. But this is not true in case of peptides.

If the pH of a peptide solution is 0, than it is not necessary that it is neutral. This is because at this pH the charges on carboxyl and amino group of amino acids in the peptide will nullify each other, but the charges present on amino and carboxyl group on the side chain of amino acid will impart some charge to the protein. Hence the overall charge will not be 0.

The pH at which the charge on a protein is zero is called as isoelectric point. This can be any pH value, not necessarily 7.

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