Immobilization alters enzyme's 3D folding Steps:

• Immobilization binds enzyme to gel, restricting molecular movement.
• This constraint affects overall protein shape without changing amino acid sequence.
• pH influences activity via ionization of side chains, which immobilization modifies by limiting flexibility.
• Graph shows shifted pH optimum, indicating structural change impacts active site.

Why C is correct:

• Tertiary structure is the 3D arrangement of polypeptide chain; immobilization distorts it via physical fixation, altering pH-dependent interactions like ionic bonds.

Why the others are wrong:

• A: Primary structure is the fixed amino acid sequence, unaffected by immobilization.
• B: Secondary structure involves local patterns like helices, preserved during immobilization.
• D: Quaternary structure applies to multi-subunit proteins; no evidence of subunit changes.

Final answer: C