1. Chapter 5: Structure and Function of Plasma Membrane

2. 5.1 Components of cell membrane

3. Fluid Mosaic Model
The plasma membrane separates a cell’s external environment
Regulates substances into and out of cells
Communicates with other cells
Fluid mosaic model: cell’s membrane is a fluid of mixed composition
Molecules are embedded within lipid bilayer (proteins, cholesterol)

5. Membrane Proteins Recognition proteins: identifies “self” cells
Receptor proteins: triggers a change in cell activity
Transport proteins: assists the movement of molecules across the membrane

7. 5.2 Passive transport

8. Diffusion Molecules tend to spread apart towards low concentrations
Semipermeable membranes allow some materials oxygen, carbon dioxide and lipids pass through
Other molecules (sugars and ions) require specific transport proteins
As molecules move across the overall concentration will reach equilibrium
Diffusion across a membrane is passive because it requires no work
Diffusion across a membrane is passive because it requires no work

9. 5.3 Active Transport

10. Against the grain
If a cell needs maintain a high concentration work must be done
Active Transport requires proteins that act as a pump molecules against the concentration gradient
Example is the Na/K pump

11. 5.4 Bulk Transport

12. Exocytosis – vesicles fuse with outer membrane and release materials
Endocytosis – vesicles form in outer membrane trapping materials outside the cell
Phagocytosis – cell “eating”
Pinocytosis – cell “drinking”