How would a cell be affected if it lost the ability to be selectively permeable?

If there's no selective permeability, the cell would be able to allow all substances into the cell, in other words, the cell will be "permeable".

Normally, the biological membranes have a selective permeability, that is to say, they let themselves through some substances more easily than others, quickly pass through the membrane, because they dissolve in the lipid bilayer.

*Hydrophobic substances rapidly cross the membrane because they dissolve in the lipid bilayer.

*The small polar molecules (like H2O and CO2) thanks to their small size, these polar molecules also cross the double lipid layer.

*Large molecules and ions pass through the membrane through specific transport proteins, such as uniport, symport or antiport.