If the plasma membrane ruptures or breaks down, then following things may happen :
(i) There will be no difference between the contents of the cell and its external environment.
(ii) Ruptured plasma membrane will allow free movement of all the substances in and out of the cell.
(iii) The cell will lose its shape as the plasma membrane provide shape to the cell.
(iv) All the metabolic activities of the cell will get affected , may even stop and cell may die .