1. Cell Membrane

2. Homeostasis Cells must maintain homeostasis in order to live
One way is by controlling the movement of water through the cell membrane

3. Cell Membrane A fluid sea of lipids in which proteins float
Allows only some materials to enter the cell

4. Phospholipid
Specialized lipid made of a phosphate head and two fatty acid tails

5. Lipid Bilayer Phospholipids form a lipid bilayer
One polar head faces the cytoplasm
Other polar head faces outside

6. Lipid Bilayer

7. Barrier
The phospholipids form a barrier through which only small, nonpolar substances can pass.

8. Proteins Nonpolar parts are attracted to inside of lipid bilayer
Polar parts are attracted to outside

9. Types of Proteins
Cell-surface markers – identify each type of cell by the kind of sugars
Attached to the surface by glycoproteins

10. Types of Proteins cont.
Receptor Proteins – enable the cell to sense its surroundings by binding to certain substances outside the cell
Causes changes in cell

11. Types of Proteins cont.
Enzymes – Proteins in the cell membrane help with important biochemical reactions in the cell

12. Types of Proteins cont.
Transport Proteins – Many substances the cell needs cannot pass through the lipid bilayer
Proteins aid the movement of these substances in and out of the cell