Question

What is the charge on the tetrapeptide lys-lys-his-glu at ph 7?

Answer 1

Answer: The charge on peptide chain lys-lys-his-glu at pH 7 is +1.

Explanation: A peptide chain is the chain formed from the condensation of two amino acids releasing $H_2O$ molecule and forming N-terminal(Nitrogen- end) and C-terminal(Carboxyl-end). The bonds formed are known as peptide bonds.

Here 4 amino acids join together forming a peptide chain

$lys-lys-his-glu$

In this peptide chain N-terminal is from lysine (lys) and C-terminal is from Glutamic acid (Glu).

At pH=7,

• The carboxyl (-COOH) groups will be deprotonated that means they will not have H-atoms and have (-1) charge.
• The Amino ($NH_2$) groups will be protonated that means they have H-atoms and have (+1) charge.

So, there are 3 amino groups present each having (+1) charge and 2 carboxyl groups each having (-1) charge.

Total charge on peptide chain = $(3\times (+1))+(2\times (-1))$

                                                   = +1