Question

Explain how a cell wall protects bacteria against a decrease but not an increase in the concentration of an external solute. Draw a cell under each condition to illustrate water movement for most solutes, does one expect the periplasmic space to have concentration that are like the cytoplasm or the medium surrounding the cell. Why?

Answer 1

when a cell is placed into a hypotonic solution (decrease concentration of an external solute), an osmotic influx of water occur that causes a cell to swell, lead to cell burst. However, this is not the case with bacteria. they possess a rigid cell wall which prevents the cell expansion. Therefore, because of the cell wall, increase in-flux of water inside the bacteria in a hypotonic solution (even pure water) leads to an increase in intracellular pressure but not in cell volume. Hance protect the bacteria from bursting.