1. Cellular Transport: Part I Diffusion and Osmosis
8 classes until break!

2. Cellular Transport Overview
Cells need to get things in and out of themselves
How does a cell get things in, and out, if itself?
What structure creates a barrier between the inside and the outside of a cell?

3. Diffusion All molecules have a certain amount of energy in them
We often experience this energy in the form of kinetic energy and thermal energy
What is kinetic energy?
What is thermal energy?
Do ALL molecules have this kind of energy?

4. Diffusion All molecules have a certain amount of energy
This causes molecules to move around, resulting in a uniform distribution of molecules
Molecules will diffuse until their concentration is balanced
Say what? Let’s look at some demonstrations…
Dye in water
Scent in air

5. Diffusion
Diffusion is: The net movement of molecules or atoms from a region of high concentration to a region of low concentration
Demonstrations:
Watch dye in water diffuse throughout the beaker
What is the solvent? What is the solute?
Scented molecules in air

6. Diffusion
Molecules move from an area of higher concentration to an area of lower concentration

7. Diffusion
How much energy did we have to exert to get the molecules to diffuse?
How much energy do cells have to exert to get important molecules to diffuse?
They take advantage of this natural phenomena!
But, wait a second. Cells have a barrier between their insides and the outside world. Can things diffuse across this barrier?
I am glad you asked! The cell membrane is SELECTIVELY PERMEABLE

8. Crossing the Cell Membrane
To understand how cells move things in and out, you need to understand the cellular membrane
What is a cell membrane made up of?
Lipids, proteins, and carbohydrates
Phospholipid bilayer
Cell membranes only allow certain materials through
Selectively permeable or Select permeability

9. Crossing the Cell Membrane
Selectively Permeable to gases and small uncharged polar molecules
What are some examples?

10. Facilitated Diffusion
Diffusion across a membrane using carrier proteins.
This is Still Passive Transport

11. Osmosis (because water is special…)
Movement of a solvent (water) across a membrane toward a higher concentration of a solute (salt)
Put another way…”water chases salt”
Water will move across a semipermeable membrane to balance the concentrations of the solution
Let’s look at a picture

12. Osmosis (because water is special…)
26 blue, 13 red vs 26 blue, 26 red
2:1 vs 1:1
26 blue, 13 red vs 52 blue, 26 red
Maintains the 2:1 ratio

13. Solution Types
Isotonic – Equal concentration in cell as compared to solution
Hint: Iso means equal or same. Ex: Isosceles Triangle
Hypotonic – Lower concentration of solutes in the solution than in the cell
Hypertonic – Higher concentration of solutes in the solution than in the cell
Remember….”water chases salt”…so which direction does water move? link

14. Passive Transport Review
The movement of substance into and out of the cell without the use of energy is called passive transport
Diffusion
Food coloring diffusing in water on its own
Scent traveling from one side of the room to the other
Osmosis
Water diffusing across membrane
Facilitated Diffusion
No energy required

15. Quiz your knowledge!
When more water goes in through a cell membrane than out of it, the solution around the membrane is…
If the solution surrounding a cell has lower concentration of solutes than the cell, water will move into a cell through osmosis, causing it to expand. What kind of solution is surrounding the cell?
When the concentrations of solutes inside and outside a cell are the same (equal), the two environments are said to be….

16. Passive Cellular Transport Summary
Three types: Diffusion, Facilitated Diffusion, Osmosis
Application to the real world: Shipwreck Lab
For Next Class:
Homework is to create a study tool for vocabulary
Vocabulary quiz next class
Finish the Shipwreck Lab