What would happen to the body if one of the organ systems stopped working?

Other parts of the body can damage

It really depends on which part of the body or which organ is not working. If it was for example the heart basically what it means is death. If it is something like reproductive organs it wont harm you instead it just means you wont be able to reproduce.

Mitochondria is the cell organelle that produced the energy that is needed in the body system in form of atp, that is why it is called the power house of the cell. energy is needed by the living organisms to carry out the activities which sustain life.  if the mitochondria is destroyed atp will not be produced. if the mitochondria is destroyed, energy production will stop and the affected living organism will not have the energy to carry out the necessary life processes; this will lead to the death of the organism.