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

8. 3.3 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.
cell membrane
protein
carbohydrate protein
chain
cholesterol
protein channel

9. 3.3 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.
cell membrane
protein
carbohydrate protein
chain
cholesterol
protein channel

10. 3.3 Cell Membrane
Cell membranes are composed of two phospholipid
layers.

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

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.
– intracellular receptor

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
–membrane receptor