Size:

• 5-10 nm wide
  

Location:

• circumference of cell
  

Function:

The plasma membrane is a lipid bilayer with scattered proteins and carbohydrates sticking out of the surface, according to the fluid mosaic model. In other words, it is the ultimate semi-permeable barrier any cell has to offer. It performs several important functions, keeping the cell in tact and functional.

• It compartmentalizes the cell, making it its own significant unit and preventing outside interference
• It provides a scaffold of sorts that keeps components of the cell orderly
• It’s selectively permeable, allowing a restricted exchange of molecules from one side of the membrane to the other
• It helps transport solutes into and out of cells
• It responds to external signals, providing a means of communication with other cells
• It regulates intracellular interaction, recognizing and exchanging information with neighboring cells
• It allows for the conversion of energy from one form to another (i.e. sunlight converted to chemical energy)
  

Related Organelles: Nucleoid