1. What do these two images have in common?
Just as this gate and these bouncers are used to protect these entrances - a cell uses a cell membrane to protect itself.

2. Cell Membrane aka plasma membrane
Forms a boundary between a cell and the outside environment
Controls the passage of material into and out of the cell

3. Cell membrane consists of a double layer of phospholipids and other molecules.

4. Phospholipid?
Referred to as polar because the “head” of the phospholipid has a charge.
Because of the charge, the phospholipid “head” can form a bond with water. It is hydrophilic (water loving).
Tails are non-polar (not charged) and are hydrophobic (water fearing).

5. Hydrophobic tails are attracted to each other and on opposite side of water!
Hydrophilic heads are on water side!

6. Cell membrane is selectively permeable.
This means the cell membrane allows some, but not all materials to cross.
Kind of like
This strainer allow passage of water through the pores but not passage of the noodles.

7. Fluid Mosaic Model
Name given by scientists to describe the arrangement of the molecules that make up the cell membrane
Fluid – because the cell membrane is flexible, not rigid
Mosaic – because the variety of molecules within the membrane is similar to the colorful textures used to make up a mosaic

8. Let’s check it out for ourselves!
Fluid Mosaic Model
Let’s check it out for ourselves!

9. But, what about a cell wall?
Plants, algae, fungi and most bacteria have a strong cell wall that surrounds the cell membrane.
NOT FOUND IN ANIMAL CELLS!

10. Cell Wall Rigid layer that gives protection, support and shape to the cell.
Cell walls of multiple cells can adhere to each other to help support an entire organism. Example: Most of the wood of a tree trunk consists of dead cells whose cell walls continue to support the entire tree.

11. Review! Which cells contain a cell membrane?
All cells contain a cell membrane.
2. Which cells contain a cell wall?
Plants, algae, fungi, and most bacteria
NOT ANIMAL CELLS!