1. How do cells take in food when they don’t have hands?

2. Diffusion
Free + zombie walk
First of all, materials must be able to go in and out of the cell.
In your opinion, what should go in?
What should come out?

3. Diffusion Diffusion is powered by the difference in CONCENTRATION.
Concentration: Amount of substance in a given amount of space.
Substances always travel from…
High concentration
Low concentration

4. Outside the cell Inside the cell HIGH concentration LOW concentration
Membrane
Outside the cell
Inside the cell
HIGH concentration
LOW concentration
Food particles (sugar)
Food particles (sugar)
LOW concentration
HIGH concentration
Waste (ammonia, CO2)
Waste (ammonia, CO2)

5. Diffusion So, does this mean that ANYTHING can come inside
the cell as long as it is in higher concentration outside?
Can you list some substances that the cell may not
want to take in no matter what?

6. Outside the cell Inside the cell
Good molecule
Bad molecule
Not all molecules can freely enter the cell.
This is called selective permeability.
Can cells reject every kind of bad molecules?

7. Osmosis Just as molecules can travel by diffusion,
water molecules can travel by diffusion too
This is called osmosis.
High
Water concentration
Low
Water concentration

8. Osmosis Activity (With gummy bears!)
Let’s predict!
What’s going to happen if we put the gummy bear in a water bath?

9. Today’s homework is…
Workbook Section 1.3