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.

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

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

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

15. 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

16. 3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes because of concentration differences.

17. 3.4 Diffusion and Osmosis
Passive transport does not require energy input from a cell.
Molecules can move across the cell membrane through passive transport.
There are two types of passive transport.
diffusion
osmosis

18. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Molecules diffuse down a concentration gradient.

19. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Osmosis is the diffusion of water molecules across a semipermeable membrane.

20. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
There are three types of solutions.
isotonic
hypertonic
hypotonic

21. 3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport proteins.
Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins.