Final answer:
Cleavage by the enzyme papain releases 2 Fab fragments and 1 Fc fragment from an IgG molecule, with the Fab fragment retaining antigen-binding capabilities and the Fc fragment contributing additional functionalities to the immune response.
Step-by-step explanation:
Cleavage by the enzyme papain releases 2 Fab fragments and 1 Fc fragment. An IgG molecule treated with papain, in the presence of cysteine, is cleaved to separate into two major components. The Fab fragments, acronym for 'fragment antigen binding,' retain the antigen-binding capacity of the intact molecule, with each fragment having approximately 50,000 Daltons molecular weight and accounting for about two-thirds of the digested IgG molecule. On the other hand, the Fc fragment, 'fragment crystallizable,' does not combine with the antigen but is instead capable of crystallization and represents approximately one-third of the papain digested IgG molecule.
This cleavage process is significant in understanding both the structural and functional aspects of antibodies in the immune system. Interestingly, many cells have receptors for the Fc portion of the antibody, adding functionality to these molecules, such as in processes like opsonization, cell lysis, and phagocytosis.