Answer:
The cell membrane is the membrane which separates a cell from its outer environment. A cell membrane is semi-permeable as it is selective in allowing the materials to enter into it and move out of the cell. The cell membrane is made up of phospholipid bilayer. The tails are made up of fatty acids which are packed inward of the layer. The phosphate head points outwards. The cell membrane also comprises of glycerol and cholesterol. Certain proteins are also embedded in the structure of the cell membrane which facilitates the movement of certain molecules across the cell membrane.