1. How Cells are Affected by and Interact with Their External Environment

2. Definition: Solution -A uniform mixture of 2 or more substances. -Can be solids, liquids, or gases, or a combination of these -Dissolved substance: Solute -Examples? -Substance in which solute dissolves: Solvent -Examples?

3. Examples of Solutions Chocolate milk Tea Milk Cytoplasm! Blood Lymph

4. Types of Molecular Movement Diffusion Passive Transport –Simple diffusion –Facilitated diffusion –Osmosis Active Transport These types involve some sort of membrane This type doesn’t

5. 1. Diffusion The random movement of molecules (liquid or gas) until they are evenly dispersed Molecules will travel down their concentration gradient –from areas of high concentration to low concentration Why? Molecules drift into a less ordered state unless some energy input keeps it orderly. https://www.youtube.com/watch?v=VY0mZUDvbH4

8. 2. Osmosis A special type of diffusion where water moves down its concentration gradient through a membrane (i.e., cell membrane) Osmosis accounts for most material exchange between internal and external environments of the cell

9. Discuss with a neighbor: Based entirely on the definition of osmosis, in what direction will the water (solvent) move? Hint: Where is there more water? Where is there less water? thin membrane

10. Types of Solutions Sketch and Label

12. In which direction do you think water will move?

15. Your Task Discuss with neighbor: Why does all of this matter for a cell? For an organism?

16. Homework due Thursday WS, Diffusion, Osmosis, Water Balance Questions?