1. Cells: Membrane Transport

2. Cell Membrane Structure
Fig. 7-2
Cell Membrane Structure
WATER
Hydrophilic
head
Figure 7.2 Phospholipid bilayer (cross section)
Hydrophobic
tail
WATER

4. Cellular Physiology: Membrane Transport Two Types of Transport:
Passive and Active
1. Passive transport
Does not require energy to transport across the membrane
Slide 3.20
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5. Passive Transport Processes
Simple diffusion
Particles tend to distribute themselves evenly within a solution
Movement is from high concentration to low concentration, or down a concentration gradient
Figure 3.8
Slide 3.23
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. Passive Transport Processes
Facilitated diffusion
Allows lipid insoluble substances (i.e. glucose) to pass through using a protein channel from high to low concentration

7. Passive Transport Processes
Osmosis – simple diffusion of water
Osmosis & Diffusion Animation
Slide 3.24b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. Cellular Physiology: Membrane Transport Two Types of Transport
2. Active transport
Requires energy to transport across the membrane
Solutes move from low to high concentration or against the concentration gradient
Slide 3.20
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. Active Transport Processes
Bulk transport
Exocytosis
Moves materials out of the cell
Material is carried in a vacuole
Vacuole migrates to cell membrane
Vacuole combines with cell membrane
Material is emptied to the outside of the cell
Slide 3.29a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. Active Transport Processes
Figure 3.11
Slide 3.29b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Active Transport Processes
Bulk transport
Endocytosis
Process of taking material into the cell by means of infoldings, or pockets, of the cell membrane
Slide 3.30a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

12. Active Transport Processes
Bulk transport
Types of endocytosis
Phagocytosis – cell eating – brings in large particles within a food vacuole
Pinocytosis – cell drinking – cells taking up liquid from the surrounding environment
Slide 3.30a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13. Active Transport Processes
Figure 3.12
Slide 3.30b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. Effects of Osmosis on Cells
Type of Solution
Animal Cell
Plant Cell
Isotonic:
The concentration of solutes (salt) is the same inside and outside the cell.
Water moves
equally into
and out of the
cell

15. Effects of Osmosis on Cells
Type of Solution
Animal Cell
Plant Cell
Hypertonic:
Solution has a higher solute (salt) concentration than the cell.
Water leaves
the cell and it
loses
turgor pressure
And causes the
cell to shrink

16. Effects of Osmosis on Cells
Type of Solution
Animal Cell
Plant Cell
Hypotonic:
Solution has a lower solute (salt) concentration than the cell.
Water enters
the cell and
Pushes against
The cell wall
Increasing the
turgor pressure
Causing the cell
to swell and possibly burst

17. What type of solution do you think this red blood cell was placed in?
A B C

18. What type of solution do you think this red blood cell was placed in?
Hypotonic!
A B C