After cleavage of C5, C5b undergoes conformational changes and exposes a binding site for C6. C5b6 binds C7 resulting in the exposure of membrane binding sites and incorporation into target membranes. The membrane-bound C5b-7 complex can then bind C8. C5b-8 acts as a polymerizing agent for C9. The first C9 bound to C5b-8 undergoes major structural changes enabling formation of an elongated molecule and allows binding of additional C9 molecules and insertion of C9 cylinders into the target membrane. The number of C9 molecules varies from 1-12 in the membrane, although polymers containing up to fifteen C9 molecules are also possible.