Answer:
This is a cell membrane.
Step-by-step explanation:
Cell membranes serve as barriers and gatekeepers. They are semi-permeable, which means that some molecules can diffuse across the lipid bilayer but others cannot. Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. The passage of large molecules like amino acids is carefully regulated.
It also gives shape to the cell.
Hope this helps.