1. Cells and Their Environment
Chapter 4
p 74-84

2. Homeostasis A biological balance
Cells, tissues, organs, and organisms must maintain a balance.
Cells do so by controlling and regulating what gets into and out of the cell.

4. Transport Passive Active
Transport that does not require chemical energy to occur
ie: diffusion and osmosis
Active
The movement of any substance across a cell membrane with the use of chemical energy
ie: Na+/K+ pump

5. DIFFUSION
Process by which molecules spread from an area of high concentration to an area of low concentration
Concentration gradient: a difference in the concentration of a substance
Examples:
Oxygen diffusing into cells
Beaker of water with food coloring
Smell of perfume in a room
***Molecules are in constant
motion

6. Diffusion animations

7. Osmosis
Diffusion of water through a membrane from an area of high concentration to an area of low concentration.
What determines the direction in which water molecules diffusion across a cell membrane?
**the concentration of water and of solutes dissolved in the solution

8. http://www. stolaf. edu/people/giannini/flashanimat/transport/osmosis

9. Think about it… What happened if you eat salty foods?
Grass wilts if you add too much fertilizer…WHY?

10. Cells can be found in 1 of 3 solutions:
HypOtonic
2. Hypertonic
3. Isotonic

11. HYPOTONIC
Concentration of solute molecules in the environment outside of the cell is lower than that in the cell.
Water moves in

12. Red blood cell

13. Hypertonic
Concentration of solute molecules outside the cell is greater than that in the cell
Water moves out

14. Isotonic
Concentration of solute molecules outside cell and inside are equal.
**equilibrium

16. Facilitated diffusion
Use of carrier to “help” move molecules across a membrane
Passive: energy Y or N?
Gradient: H to L
Example: glucose

17. Filtration Type of Transport: Passive
Using pressure to push something through the cell membrane
Energy needed??
Example…what organ in your body filters

18. Active transport
Movement of substances through a membrane from a low to high concentration with the use of energy.
ATP: energy form
Usually Low to high concentration
“Against a gradient”
Example: Na/K pump.

19. Active Transport

20. Some molecules are too large to pass thru membrane
Some molecules are too large to pass thru membrane!!! Even with use of energy
Endocytosis…movement of substances into the cell by transport vesicles into the cell.
Exocytosis… movement of substances outside of the cell by transport vesicles into the cell

21. Endocytosis

22. Exocytosis