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

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

4. 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 outside cell inside cell

5. 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 outside cell inside cell

6. Cell membranes are composed of two phospholipid layers.

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

8. cell membrane • Cell membranes are composed of two phospholipid layers. • The cell membrane is made of a phospholipid bilayer. • Phospholipids are arranged with the hydrophilic heads pointing outwards and the hydrophobic tails pointed inwards.

9. carbohydrate chain protein cell membrane cholesterol protein protein channel • 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.

10. carbohydrate chain protein cell membrane cholesterol protein protein channel • 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 cell membrane is made up primarily of Lipids, but Proteins and Carbohydrates are also found there.

11. carbohydrate chain protein cell membrane cholesterol protein protein channel • 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.

12. carbohydrate chain protein cell membrane cholesterol protein protein channel • Cell membranes are composed of two phospholipid layers. • The fluid mosaic model describes the membrane. • Molecules that make up the membrane are always moving.

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 are able to 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.

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

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

19. Chemical signals are transmitted across the cell membrane. • Receptors bind with ligands and change shape. • There are two types of receptors. • intracellular receptor • Chemical signals are sent on a ligand through the membrane and bind to a receptor inside the cell itself.

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

21. 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 • Receptors are found embedded in the membrane and allow for communication between the cell and the outside world.