1. Homeostasis & Transport
Ch.5

2. (5-1) Homeostasis
Cell membranes control what goes in & out

4. Passive Transport
Movement of materials across a cell membrane without the use of E (ATP)
4 Types:
Diffusion
Osmosis
Facilitated Diffusion
Ion Channels

5. Diffusion
Movement of molecules from an area of high concentration to low conc.

6. Concentration Gradient
Difference in conc. of molecules across a membrane
“Down the gradient”
Move from high to low conc.

7. Equilibrium Conc. is equal on both sides of the membrane
Diffusion ends

8. Diffusion Across a Membrane
Depends upon size, shape, & chemical makeup
Easy to diffuse:
Small
Nonpolar
(dissolve in
lipids)

9. Osmosis
Water diffusion across a membrane

10. Hypotonic Solution
Solute conc. is higher inside & water conc. is higher outside the cell
Water moves into the cell
May cause cytolysis
(cells burst)

11. Hypertonic Solution
Solute conc. is higher outside & water conc. is higher inside the cell
Water moves out of the cell
May cause plasmolysis
(cells shrink)

12. Isotonic Solution
Solute & water conc.’s are equal on both sides of the membrane
Equilibrium

13. Isotonic
Hypertonic
Hypotonic

14. How Cells Deal with Osmosis
Contractile vacuoles: collect
excess water & pump it out of
the cell
Requires E
Turgor pressure: P that water exerts against the cell wall

15. Facilitated Diffusion
Carrier proteins assist diffusion across a membrane
Specific to certain molecules (glucose)

16. Diffusion via Ion Channels
Ion channels assist diffusion across a membrane
Some always open, others gated
Common ions:
Na+ K+
Cl-
Ca2+

18. (5-2) Active Transport
Movement of a substance across a cell membrane against a conc. gradient
Requires E

19. Na-K Pump
Carrier protein that transports K+ into & Na+ out of the cells
Helps conduction of electrical impulses in nerve cells

20. Endocytosis Cell surrounds & engulfs substances 2 Types:
Pinocytosis: fluids or solutes
Phagocytosis: large particles

21. Exocytosis
Vesicle inside a cell fuses w/ the cell membrane & releases contents outside of cell
Proteins, waste, toxins