At pH 4 how many charged groups are present in the pentapept

At pH 4, how many charged groups are present in the pentapeptide ADHSL?

a) 1

b) 2

c) 3

d) 4

Solution

Answer: (b).2

ADHSL = Ala-Asp-His-Ser-Leu

At pH4 only the carboxylic groups are ionized

Therefore Asp side chain and leu-COOH groups are charged = 2