Choose the correct option for structures of A and B, respectively.

Question

Canvas Classes · Accepted Answer

Step 1: Understand amino acid ionisation

The amino acid shown is valine:

It has two ionisable groups:
-  (acidic, )
-  (basic, )

Step 2: At pH = 2 (strongly acidic)

Both groups are protonated:
-  remains as  (pH < )
-  is protonated to

(cationic form)

Step 3: At pH = 10 (strongly basic)

Both groups are deprotonated:
-  →  (pH  )
-  →  (pH  )

(anionic form)

Answer: Option (a)

Key Points to Remember:
- At low pH: amino group protonated (), carboxyl group neutral ()
- At high pH: amin

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