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.
The cell membrane is made of a phospholipid bilayer.
Head is polar & contains a –PO4 (phosphate) group & glycerol
Tail contains 2 fatty acid chains that are nonpolar

11. Cell membranes are composed of two phospholipid layers.
There are other molecules embedded in the membrane.
Cholesterol (strength)
Proteins (help things pass)
Carbohydrates (identification tags)
protein
cholesterol
carbohydrate
chain
protein channel
cell membrane

12. Cell membranes are composed of two phospholipid layers.
The fluid mosaic model describes the membrane.
FLUID - because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid.
MOSAIC - because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

13. Cell membranes are composed of two phospholipid layers.

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

16. Cell membranes are composed of two phospholipid layers.
The cell membrane is selectively permeable.
Some molecules can cross the membrane while others cannot.
Enables cell to maintain homeostasis.
Molecules can cross either with or without energy.
Small, nonpolar molecules easily pass through the membrane. Others use proteins or vesicles.

18. Chemical signals are transmitted across the cell membrane.
Receptors (a protein that detects a signal molecule and performs an action in response) bind with ligands and change shape.
There are two types of receptors.

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

20. 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