1. Homeostasis
Maintenance of an internal environment suitable for that living organism
Cells maintain homeostasis by regulating the movement of substances across the cell membrane.

2. Diffusion Move from HIGH to LOW concentration movement of water
“passive transport”
no energy needed
movement of water
diffusion
osmosis

3. Diffusion
Molecules move to equalize concentration

4. How a selectively permeable Membrane Might Work

5. Process of Facilitated Transport
Protein binds with molecule
Shape of protein changes
Molecule moves across membrane

6. http://highered. mcgraw-hill

7. Osmosis Water is very important, so we talk about water separately
diffusion of water from HIGH concentration of water to LOW concentration of water
across a semi-permeable membrane

8. Concentration of water
Direction of osmosis is determined by comparing total solute concentrations
Hypertonic - more solute, less water
Hypotonic - less solute, more water
Isotonic - equal solute, equal water
hypotonic
hypertonic
water
net movement of water

9. Managing water balance
Hypotonic
a cell in fresh water
problem: gains water, swells & can burst
water continually enters Paramecium cell
solution: contractile vacuole
pumps water out of cell
ATP
plant cells
turgid
ATP
freshwater

10. Managing water balance
Hypertonic
a cell in salt water
problem: lose water & die
solution: take up water or pump out salt
plant cells
plasmolysis = wilt
saltwater

11. Osmosis…
.05 M
.03 M
Cell (compared to beaker)  hypertonic or hypotonic
Beaker (compared to cell)  hypertonic or hypotonic
Which way does the water flow?  in or out of cell

12. Managing water balance
Isotonic
animal cell immersed in mild salt solution
example: blood cells in blood plasma
problem: none
no net movement of water
flows across membrane equally, in both directions
volume of cell is stable
balanced

13. Let’s Get Active!!!
Active Transport involves the movement of molecules against their concentration gradient. It requires energy (usually in the form of ATP) to move across the membrane.

14. exocytosis
FLUID OUTSIDE CELL
CYTOPLASM
Figure 5.19A

15. ENDOCYTOSIS
Figure 5.19B

16. Transport Across The Membrane
Endocytosis (pinocytosis, phagocytosis): phagocytes (macrophages)- molecules are coming into cells
Exocytosis: release of proteins, hormones, neurotransmitters

17. THREE KINDS OF ENDOCYTOSIS.

18. Let’s Hear it For Transport

19. Transport summary simple diffusion facilitated diffusion
ATP
active transport