At this point in writing your tutorial, you have to find a way to get across to the students the importance of a cell wall to a bacterium. how do you convey that the bacterial cell will be at the mercy of its environment? the cell wall will need to act as a support mechanism to neutralize the inflow or outflow of water that would alter the shape of the cell. the cell cannot search out for a better place in the environment that has more available water; or if there is water that it has a high enough solute concentration that the cell will not gain water. because that's the problem for a bacterial cell, it cannot control the tonicity due to solute concentrations in the surrounding water. water will flow in or out depending on solute concentrations and the only thing a bacterial cell can do to keep from collapsing due to water loss or rupturing due to too much water coming in is to have a strong cell wall that will hold its shape regardless of the osmotic pressures. the rigidity of the cell wall will maintain a set shape regardless of water flow. the proteins and lipids that anchor the cytoplasmic membrane to the cell wall will tether the membrane to the peptidoglycan layer so that when environmental conditions result in the loss of water from the cell, the membrane will not collapse in on itself. similarly, changes in environmental conditions that would result in the inflow of water would expand the volume of the cell to the limits of the cell wall and no more.