1. The Cell Membrane http://upload.wikimedia.org/wikipedia/commons/0/08/Cell_parts.png

2. The current model that scientists use to explain the structure of the cell membrane is known as the fluid-mosaic model. The cell membrane is made of a phospholipid bilayer. http://academic.brooklyn.cuny.edu/biology/bio4fv/page/lipos.gif

3. The phospholipid has two parts: 1. A phosphate head that is hydrophilic (attracted to water) 2. A lipid tail that is hydrophobic (repelled by water) http://www.ibiblio.org/virtualcell/textbook/chapter3/cms1.htm

4. Due to these properties the phospholipids can self-assemble. This means that if you mixed phospholipids in water they would form a double- layered structure. http://www.ibiblio.org/virtualcell/textbook/chapter3/cms1.htm

5. Also due to these properties of the phospholipid bilayer the cell membrane is "selectively permeable"--only certain things can enter the cells. Because the cell membrane is mostly lipid, it only allows lipid-soluble (non-polar) substances such as oxygen, carbon dioxide, and steroids to go through without help. Water-soluble (polar) substances such as glucose, amino acids, ions (potassium K+ calcium Ca+ Na sodium) and water need the help of proteins in the membrane for transport.

6. Proteins in the Cell Membrane Embedded in the cell membrane are proteins. ( The proteins in the cell membrane are like chocolate chips in in a chocolate chip cookie).

7. There are four types of proteins in the cell membrane. 1.Receptors: globular proteins that bind to signal molecules such as hormones. 2. Pore proteins: have openings that allow polar molecules like water to pass through.

8. Channel proteins: help move things like ions through the cell membrane. These are also known as “pumps” 4. Glycoprotein: identify the cell as "self" or part of the body, allows the cell to recognize other cells. These proteins have a carbohydrate attached them that identifies the cell. These are also known as “marker” proteins.

10. Cholesterol is also found in the cell membrane; it helps to stabilize the phospholipid bilayer. Cell Membrane Movie Build Your Own Cell Membrane