Final answer:
The enzyme papain is used to cleave IgG just below the disulfide bonds, leaving them intact and resulting in a divalent Fab fragment and multiple degraded Fc fragments.
Step-by-step explanation:
The student's question is regarding the enzymatic cleavage of an immunoglobulin G (IgG) molecule. Specifically, the cleavage by the enzyme papain just below the disulfide bonds while leaving them intact results in the release of one divalent Fab fragment and degrades the Fc into multiple fragments. When IgG is treated with papain in the presence of cysteine, the molecule separates into two major fragments: the Fab, which retains the antigen-binding capacity, and the Fc, which can crystallize and does not combine with the antigen. Each of these fragments has a molecular weight of approximately 50,000 Daltons, with the Fab fragment accounting for about two-thirds and the Fc fragment for one-third of the papain-digested IgG.