Answer:
Phospholipid bilayer.
Explanation:
The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is defined as a biological membrane that separates the interiors of a cell from its external environment.
The plasma membrane has a function that protects the cell from its external environment, mediates cellular transport, and transmits cellular signals.
It is composed of a lipids bilayer (phospholipids and cholesterol), (phospholipid is a lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group) with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules which hence, regulates the movement of substances in and out of cells. Plasma membranes is very flexible in order to allow cells change form example, red blood cells change shape as they pass through narrow capillaries.
