2. How does diffusion through the cell membrane lead to homeostasis?

3. What is diffusion? The net movement of particles from where they are more concentrated to where they are less concentrated. What do we mean by concentration? The amount of a substance

4. It’s all about concentration

5. Why does diffusion occur? Because molecules are always… MOVING

6. Why are particles always moving? ENERGY Particles are in constant motion because they have energy

7. What is the end result of diffusion? Even distribution of particles…. Dynamic Equilibrium

8. At this point, the number of particles have spread themselves out equally throughout the beaker. Are the particles still moving after dynamic equilibrium has been reached? YES Dynamic Equilibrium

9. An illustration of diffusion:

10. Two Conditions for Diffusion: 1)There must be a concentration gradient 2) There must be no barrier blocking the movement of particles.

11. What is a concentration gradient? The difference in concentration between a region of high concentration and a region of lower concentration. Does this picture illustrate a concentration gradient?

12. Identify which pictures illustrates a concentration gradient.

13. What do we mean by a barrier? Will diffusion take place? YES Will diffusion take place now? NO The particles must be free to move down their concentration gradient in order for diffusion to occur.

14. Does diffusion take place across the cell membrane? Yes, the cell is: Selectively Permeable

15. Cell Membranes are: Selectively Permeable A selectively permeable membrane allows some substances to cross the membrane more easily than others and blocks the passage of other substances altogether.

16. Why are some substances able to pass? Small molecules are more likely to get through.

17. Helping Cells Survive Cell membranes must help organism maintain HOMEOSTASIS by controlling what substances enter or leave the cells. To stay alive, a cell must exchange materials such as food, water, and waste with its environment.

18. What is the main job of the cell membrane? Cell membranes helps organisms maintain _____________ by controlling what substances may enter or leave cells To stay alive, a cell must exchange materials such as food, water, & wastes with its environment HOMEOSTASIS & TRANSPORT