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

2. Cell membranes are composed of two phospholipid layers.

3. Cell membranes are composed of two phospholipid layers.
The cell membrane has two major functions.
cell membrane

4. 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
cell membrane
outside cell
inside cell

5. 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

6. Cell membranes are composed of two phospholipid layers.

7. Cell membranes are composed of two phospholipid layers.
The cell membrane is made of a phospholipid bilayer.
cell membrane

8. Cell membranes are composed of two phospholipid layers.
The cell membrane is made of a phospholipid bilayer.
There are other molecules embedded in the membrane.
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

9. Cell membranes are composed of two phospholipid layers.
The cell membrane is made of a phospholipid bilayer.
There are other molecules embedded in the membrane.
The fluid mosaic model describes the membrane.
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

10. Cell membranes are composed of two phospholipid layers.
Form a double layer surrounding a cell.
Composed of a charged phosphate group, glycerol and 2 fatty acid chains
Outside (head) is polar; inside (tails) is nonpolar
Other molecules:
Cholesterol: strengthens
Proteins: cell identification and movement of molecules
Carbohydrates: “antennae” for cell identification

11. Fluid Mosaic Model
Describes the arrangement of molecules making up the cell membrane
The membrane is flexible like a fluid and has a variety of molecules like a mosaic.
Think of “Jello” gelatin with fruit

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

13. Selective Permeability
Allows some materials to cross
Enables a cell to maintain homeostasis
Molecules can cross in a variety of ways
Another term: semipermeable

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

15. Chemical signals are transmitted across the cell membrane.
Receptors bind with ligands and change shape.
There are two types of receptors.
Intracellular: located inside a cell; bind to molecules that can cross a membrane
Membrane: located in the membrane; bind to molecules that cannot cross the membrane; a change in shape transmits the message to the cell interior

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

17. 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