SimScience - Membranes - Advanced, page 15

Another look at cell membranes

All animals and plants, including humans, are made up of tiny cells - little packets of life. There are about 60 trillion (6x10¹³) cells in each one of us. Just as we pass food through or mouths when we eat, cells must be able to pass chemicals though the cell membrane to fuel the life processes inside. There are many different protein molecules in the cell membrane which take an active role in regulating the flow of substances into and out of the cell.

Common to all cells is the outer plasma membrane (*) composed of a bilayer of amphiphilic lipid (*) molecules. The picture below shows a bilayer with the hydrophilic heads outside (top and bottom) and the hydrophobic tails inside (together).

SEE: Revealing the nature of the cell membrane. The story of the discovery of cells and steps to understanding the cell membrane.

SEE: Cell membranes. What functions do they perform? How are they similar? How thick are they?

Although science has made many important discoveries about how cells and cell membranes work, these subjects are not yet fully understood.