Treatment of an IgG molecule with papain yields which fragments?

• A Two Fab fragments and one intact Fc fragment held together by disulfide bonds
• B Two Fab fragments and one Fc fragment, all separate ✓
• C One F(ab')2 fragment and two small Fc-derived peptides
• D One Fab fragment and one F(ab')2 fragment

Explanation

Papain cleaves IgG above the hinge region disulfide bonds, releasing two separate monovalent Fab fragments that bind antigen but cannot cross-link it, plus one intact Fc fragment carrying complement fixation and Fc receptor binding sites. Pepsin cleaves below the hinge, generating one bivalent F(ab')2 fragment and degrading the Fc portion into small peptides. This distinction between papain and pepsin cleavage is a repeatedly examined fact in Indian entrance examinations.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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