1. Plasma Membrane: Structure & Function Objective 2.03: Maintenance of Homeostasis Movement Into & Out of the Cell

2. Plasma Membrane The Plasma Membrane & Cell Membrane are the same thing! In an Animal Cell, it is the boundary between the inside and outside of the cell. It is crucial in maintaining the cell’s homeostasis!! It is selectively permeable, meaning it is choosy about what enters and leaves the cell. It keeps nutrients in, and harmful substances out

3. Structure of the Plasma Membrane The plasma membrane is a Phospholipid Bilayer (Phospholipid = Fat, Bilayer = 2 layers) and has protein embedded in it. Remember, lipids do NOT dissolve in water, so that is why cells stay together in your body that is full of water! The round structures with tails are the Lipids. The big blue structure is the Protein.

4. More on the Phospholipids… The “heads” are hydrophilic (polar) and are attracted to the water inside and outside of the cell. The “tails” are hydrophobic (non polar) and do NOT like the water. The tails point to the middle of the plasma membrane.

6. Why is it called the Fluid Mosaic Model? Fluid: because the phospholipids and proteins are always moving around in the plasma membrane. Mosaic: because the large protein make a pattern within the plasma membrane.

7. So how do things get in & out?? Small things are able to squeeze through the phospholipid bilayer and do not cost the cell any energy. Large things must be pumped into the cell through one of the large proteins and this costs the cell energy!