All life forms on Earth exist either as single cells or as collections of cells that have a plasma membrane at their periphery (though some cells have cell walls outside their plasma membrane). Why do you think the plasma membrane exists in all living things? Why aren't there living things that don't have a membrane at their periphery?© BrainMass Inc. brainmass.com June 3, 2020, 8:21 pm ad1c9bdddf
The critical idea in this problem is DIFFUSION. All chemical substances will diffuse down a concentration gradient ie from high concentration to lower and lower concentration unless confined by a barrier. The barrier could be a container like the plastic ...
The plasma membrane is the boundry between a living cell and the non-living environment. Without this boundry living systems would become diluted into the environment and live would not be possible.