Answer:
Hi there!
Your answer is:
It is very important for the cell membrane to be semi-permeable because the ability to pick and choose what comes in and out of the cell keeps the cell safe! The membrane can choose to block out nasty germs and can also choose to get rid of internal waste.
An example of when this is important is in this scenario:
Let's say the cells are in a really salty solution. Naturally, salt will want to pull the water out of the cell. If the membrane wasn't semi permeable, the water would listen to the salt and leave the cell. This would cause cell death. BECAUSE the membrane is semi permeable, they can choose not to give the salt any water, keeping them alive
Hope this helps