Question

Why is it concidered hypertonic when a bacteria cell is placed in a solution containing 5% NaCl??

Answer 1

The normal sea water contain approximately 3.2-3.8% NaCl.

The molecular weight of NaCl is 58g/mol.
5% w/v NaCl solution is 1.16 M solution.
For most of the cell, themolarity insid is 150mM.
It can be concluded that a 1.16M solution is strongly hypertonic relative to the bacterial cells.

When a bacterial cell is placed in this solution , as the concentration of water is more inside the cell than the outside, so due to water potential water moves from an area of greater water potential to lower water potential resuts plasmolysis and death of the cell.