Question

JEE ADVANCED CHEMISTRY QUESTION SEPTEMBER 2020

Answer 1

The structure of peptide is given below ,

if the absolute values of net charge of the peptide at pH = 2, pH = 6 and pH = 1w are |z₁| , |z₂| and |z₃| , respectively, then what is |z₁| + |z₂| + |z₃| ?

solution : at pH = 2 , NH₂ (1) and NH₂ (2) of Tyrosine and Lysine is positively charged and each of them has + 1 charge. so total charge , |z₁| = 2

at pH = 6, NH₂ of Lysine (+1) , COOH of glutamic acid (-1), so total charge |z₂| = |+1 - 1| = 0

at pH = 11, COOH of glutamic acid (-1) , COOH of Lysine (-1) and OH of phenol (-1) so total charge, |z₃| = |-1 -1 -1| = 3

Therefore the value of |z₁| + |z₂| + |z₃| = 2 + 0 + 3 = 5