1. 3.3 Cell Membrane KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

2. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers.

3. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. cell membrane

4. 3.3 Cell Membrane 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. 3.3 Cell Membrane 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. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers.

7. 3.3 Cell Membrane cell membrane Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer.

8. 3.3 Cell Membrane cell membrane 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. Carbohydrate chain Protein Protein channel Cholesterol Protein

9. 3.3 Cell Membrane cell membrane 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. protein cholesterol protein carbohydrate chain protein channel 1 2

10. 3.3 Cell Membrane 1.Carbohydrate molecules are attached to some proteins (identification markers) 2.Also has protein molecules running through lipid bilayer (channels & pumps)

11. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

12. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

13. 3.3 Cell Membrane Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

14. 3.3 Cell Membrane Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors.

15. 3.3 Cell Membrane Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. – –intracellular receptor

16. 3.3 Cell Membrane 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