1. KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

3. Cell membranes are composed of two phospholipid layers.
The cell membrane has two major functions.
forms a boundary between inside and outside of the cell
controls passage of materials
cell membrane
outside cell
inside cell

4. There are other molecules embedded in the membrane
There are other molecules embedded in the membrane. The fluid mosaic model describes the membrane
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

5. Cell membranes are composed of two phospholipid layers.
The cell membrane is selectively permeable.
Some molecules can cross the membrane while others cannot.

6. l Cell Membrane analogies: Fluid Mosaic Model A sandwich of molecules
Phospholipid bylayer
Functions-protective boundary between the inside and outside environment of the cell
Controls transport of materials in and out
Maintain homeostasis
Maintains selective permeability
Communicates, signals, and identifies cells and molecules

7. : Structure: Hydrophilic polarhead-phosphate group
Hydrophobic fatty acid tails (2)
Transport protein channels
Carbohydrate chains
Protein receptors
Cholesterol-strength and stability

8. Three types of Membrane Proteins
1.Channel Proteins are transport proteins-provide passageways for sugars, ions, amino acids
“Gates to the Cells Interior”
2. Marker Proteins-cell surface markers, cell identifiers,aids the immune system.
“Name Tags
3. Receptor Proteins-changes shape-send signals (for ex. Binds with Hormones (a ligand)
“Informers of the Cell”
Intracellular receptors
Membrane receptors

9. Chemical signals are transmitted across the cell membrane.
Receptors bind with ligands and change shape.
There are two types of receptors.
intracellular receptor
membrane receptor