JEE Advanced · Chemistry · 29. Biomolecules

The structure of a peptide is given below.
If the absolute values of the net charge of the peptide at $pH = 2, pH = 6,$ and $pH = 11$ are $|z_{1}|, |z_{2}|,$ and $|z_{3}|,$ respectively, then what is $|z_{1}| + |z_{2}| + |z_{3}|$ ?

A 5
B 10
C 15
D 20

Verified Solution

Answer & Solution

Correct Answer

(A) 5

Step-by-step Solution

Detailed explanation

The structure of tripeptide will be as followed at

PH = 2

(in highly acidic medium)

hence

|z_{1}| = 2

pH = 6

(in approximately neutral solution it will be

Hence

|z_{2}| = 0

pH = 11

(in highly basic medium) the structure will be

Hence

|z_{3}|

will be

3

.Therefore

|z_{1}| + |z_{2}| + |z_{3}| = 2 + 0 + 3 = 5

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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The structure of a peptide is given below.If the absolute values of the net charge of the peptide at pH=2, pH=6, and pH=11 are z1,z2, and z3, respectively, then what is z1+z2+z3?

Step-by-step Solution

The structure of a peptide is given below.
If the absolute values of the net charge of the peptide at $pH = 2, pH = 6,$ and $pH = 11$ are $|z_{1}|, |z_{2}|,$ and $|z_{3}|,$ respectively, then what is $|z_{1}| + |z_{2}| + |z_{3}|$ ?