Notes

Cell Membrane: All living cells and many of the tiny organelles internal to cells are bounded by thin membranes. These membranes are composed primarily of phospholipids and protein and are typically described as phospholipid bi-layers.

Phospholipids: {phos-pho-lip-id} A lipid containing a phosphate group in its molecule.

Lipid: Any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.

Phosphate: A salt or ester of phosphoric acid, containing a group such as -OPO (OH)2.

Cell membrane is the semipermeable membrane surrounding the cytoplasm of a cell.

According to the cell theory, cells are the main unit of organization in biology. Whether you are a single cell or a blue whale with trillions of cells, you are still made of cells. All cells are contained by a cell membrane that keeps the pieces inside. When you think about a membrane, imagine it is like a big plastic bag with some tiny holes. That bag holds all of the cell pieces and fluids inside the cell and keeps any nasty things outside the cell. The holes are there to let some things move in and out of the cell.