n which case did the Supreme Court rule that basic procedural rights must be present when decisions are made about the disciplining of inmates for serious infractions of prison rules

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.

C; skin, is the answer!