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Cell Membrane Information Worksheet
Composition of the Cell Membrane & Functions
The cell membrane is also called the plasma membrane. It is made of a
phospholipid bilayer. This double layer of lipids is also known as a fluid mosaic
because the phospholipids that make up the membrane lie next to each other but
are not connected. This gives the cell membrane a fluid motion. The cell
membrane is embedded with many different proteins and other substances that
allow some selective materials to enter and leave the cell. The many different
substances that are embedded in the cell membrane give it a look similar to a
mosaic in the art world which uses pieces of tile to form a picture or design.
The phospholipids have a polar, hydrophilic (water attracting) head and two
nonpolar, hydrophobic (water repelling) tails. Phospholipids can move laterally
and allow water and other small molecules to pass through into or out of the cell.
Since the cell membrane is mostly made of lipids, only lipid soluble substances
such as oxygen and carbon dioxide can pass through in this way. Other
substances that are water soluble need to pass through openings created by
different kinds of proteins which are embedded in the membrane. Water soluble
substances include molecules like glucose, amino acids, ions and water.
