1. The Cell in Action Exchange with the Environment

2.  What would happen if a factory’s power was shut off?  Or their supplies never arrived?  Or they couldn’t get rid of its garbage?

3. Cells are like factories  Both need to obtain energy and get things in (nutrients) and out (wastes)  These things keep the cell healthy and able to divide  Cells dividing is what allows organisms to grow  What part of the cell controls the things in and out of the cell??  CELL MEMBRANE!

4. What is Diffusion?  Diffusion- the movement of particles from regions of higher density to regions of lower density Let’s visualize it

5. Diffusion of water  The diffusion of water is called osmosis  Osmosis- the diffusion of water through a semipermeable membrane  Semipermeable??  Semi – partially  Permeable- accessible/permeable/passable It means only certain substances can pass through Let’s see it in action!!

6. The Cell and Osmosis  Cells need a certain amount of water in them  Not too much and not too little!  If red blood cells could burst if they had too much water  Plants wilt if they don’t have enough water in their cells

7. Moving Small Particles  Small particles (like sugars) cross the cell membrane through passageways called channels  The channels are made of proteins  They pass through the channels by either active or passive transport

8. Passive Transport  Passive transport- the movement of substances across a cell membrane without the use of energy by the cell  Examples: diffusion and osmosis Let’s see it!

9. Active transport  Active transport- the movement of substances across the cell membrane that requires the cell to use energy  Usually is particles moving from an area of low concentration or an area of high concentration  Or…low density to high density Let’s see it!

10. Moving Large Particles  Small particles cross the cell membrane by  Diffusion  Active transport  Passive transport  Large particles use the processes called endocytosis and exocytosis

11. Endocytosis  Endocytosis- the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell  Vesicle- sacs formed from pieces of cell membrane cell PROTEIN

12. Exocytosis  Exocytosis- the process in which a cell releases a particle by enclosing the particle in a vesicle that then moves to the cell surface and fuses with the cell membrane  Things like wastes..EXIT (EXO) the cell

13. Endocytosis and Exocytosis Let’s see it in action!!

14. Review  Describe diffusion  How is osmosis different than diffusion?  Why is osmosis important for cells?  Describe passive transport  Is it high to low concentration or low to high?  Does it require energy?  Describe active transport  Is it high to low concentration or low to high?  Does it require energy?  Describe endocytosis  Describe exocytosis

15. Review  How would the following materials get through a cell membrane and into a cell  Pure water  Sugar entering a cell with a high concentration of particles  Sugar entering a cell with a low concentration of particles  A protein  How would wastes get out of a cell?