3. Environment
The simplest definition of an ecosystem is that it is a community or group of living organisms that live in and interact with each other in a specific environment.
Answer:
b.Movement of phospholipids in the plasma membrane from one monolayer to the other requires the polar or charged head groupd to enter the hydrophobic interior of the lipid bilayer. This process requires a large positive change in free-energy, thus making this type of movement unlikely without an input of energy
The plasma membrane serves a protective function for the cell and is a selective membrane for particles entry
