Question

This peptide, Lys-Glu-Ala-Asp-Arg-Met-Arg, will be isoelectric at what pH range?

A. neutral

b. acidic

c. basic

d. very basic

The answer is C. Can you please explain how to figure this out.

Answer 1

Answer

Lys-Glu-Ala-Asp-Arg-Met-Arg: This peptide consists of Amino Acids. So, let me divide this peptide into individual Amino Acids

Amino Acid   Charge

Lys-> Lysine Positive

Glu->Glutamic Acid Negative

Ala->Alanine Neutral/No charge

Asp->Aspartic acid Negative

Arg->Arginine Positive

Met->Methionine Neutral/No Charge

Arg->Arginine Positive

Total Charge of the Peptide = Positive + Negative + Neutral + Negative + Positive + Neutral + Positive

= Positive

To become isoelectric i.e of Zero Charge, the pH must be basic (which gives negative concentration or charge)