1. Diffusion and Osmosis
Pre-AP Biology

2. Bellwork You have a raisin and you stick it in a…
Glass of Water – What will happen to the raisin?
Glass of Salty Water from the Ocean- What will happen to the raisin?

3. Objectives Distinguish between diffusion and osmosis
Identify environmental factors that influence the rate of diffusion
Define tonicity
Distinguish between isotonic, hypotonic and hypertonic solutions

4. Key Terminology
Diffusion
Osmosis
Isotonic
Hypotonic
Hypertonic

5. Solution Solution is made of the solute and the solvent
Solute is the substance dissolved in the solvent
Examples of solute-glucose, NaCl, sucrose
Solvent is the dissolving agent- what the solute is dissolved in
Example of solvent - water

6. Diffusion-Movement of Solutes
Solute molecules move from a high concentration to a low concentration.
Solutes move away from the most concentrated region
Movement of dye in a beaker of water

7. Diffusion How quickly the molecules move dependent on temperature
Higher the temperature the faster the molecules will move

8. Diffusion at Equilibrium
Diffusion continues until they reach equilibrium-same concentration of molecules throughout the solution
Molecules at equilibrium continue to move but no net movement- Don’t move in only one direction, instead move in all directions equally.

9. Practice Utube Problem
10% glucose, 1% starch
0% glucose, 0% starch
Membrane permeable to glucose
but not to starch

10. Osmosis Definition: Diffusion of water
Water will move in the direction where there is a high concentration of solute.

11. Osmosis-Diffusion of Water
Water moves in response to differences in concentration of solutes (number of solutes per volume) between solutions.
The size of the solute does not matter only the number of solutes per volume
Will water move towards Solution A or Solution B? Explain

12. Example: Salt Sucks
Salt is a solute, when it is concentrated inside or outside the cell it will pull water in its direction.

13. Tonicity:Compare two solutions separated by a membrane
Compare solute concentration inside and outside a cell
Isotonic – Concentration of salt equal between the two solutions – no net movement of water

14. Tonicity (cont)
Hypotonic- Comparing the solution outside and inside of cell, the hypotonic solution is the solution with the lower solute concentration

15. Tonicity (cont.)
Hypertonic- Comparing the solution inside and outside the cell, the hypertonic solution has the higher concentration of solutes

16. Think-Pair-Share
Extensive irrigation on Phoenix golf courses causes salts to accumulate in the soil. Why might this be harmful to the turf grass on these courses?
3. Think-pair-share
teacher presents a question
teacher gives wait time for student to form answer
teacher instructs students to share their answer with a partner
teacher calls on non-volunteers to share with the class 3

17. Red Blood Cells Isotonic solution outside- no net movement of water
Red blood cell – regular shape
Hypotonic solution outside- water moves into cell
Red blood cell – burst
Hypertonic solution outside- water moves out of cell
Red blood cell – shrivel

18. Red Blood Cells in solutions of varying osmolarity.
100 mos
200 mos
300 mos
400 mos
500 mos
hypotonic
isotonic
hypertonic

19. Think-Pair-Share
You have been sick for a couple days unable to keep any food or drink in your stomach resulting in severe dehydration. You are taken to the hospital and given intravenous solutions. The intravenous solutions are a saline solution not pure water. Why?
3. Think-pair-share
teacher presents a question
teacher gives wait time for student to form answer
teacher instructs students to share their answer with a partner
teacher calls on non-volunteers to share with the class 3

20. Summarize two key points in your note taker in your own words!
Paraphrase
Summarize two key points in your note taker in your own words!
6. Paraphrase
student writes down one or two main ideas directly from the text or notes
student now paraphrases these ideas in their own words
teacher provides feedback 6