1. Intro to Diffusion Drill: Outcome:
Would you rather stand in a very crowded room, which made it hard to move through, or in a room that was less crowded, which made it easy to move through?
Briefly explain.
Outcome:
Explain how diffusion works.
Discuss the purpose of diffusion in the body.
Draw the movement of water/salt due to diffusion.
Most people do not like to stand in crowded areas, so they would choose to move away from the crowd to another area with fewer people. This is exactly like diffusion because molecules will spread out evenly and away from the crowded source. (Like spraying perfume in the back of the room… it will eventually diffuse throughout the room and someone will smell it in the front of the room)

2. The Plasma Membrane
2/14/2019
Cell Membrane
The cell membrane is flexible and allows a unicellular organism to move
G. Podgorski, Biol. 1010

3. Structure of the Cell Membrane
The Plasma Membrane
2/14/2019
Structure of the Cell Membrane
G. Podgorski, Biol. 1010

4. Slide 1
What is Diffusion?
Diffusion: The movement of molecules from an area of high concentration to an area of low concentration.
The dye in the water goes in as a single drop and slowly diffuses throughout until it is even distributed (a solution).

5. Diffusion The molecules will pass in or out of a cell membrane.
Slide 2
Diffusion
The molecules will pass in or out of a cell membrane.
Always from high to low concentration
Way to abbreviate: High Concentration  [High]
Way to abbreviate: Low Concentration  [Low]
Anything that is abbreviated with square brackets [X] means the concentration of “X”

6. Diffusion: Salt Movement
Slide 3
Diffusion: Salt Movement
Ex: Which way would the salt molecules move?
Explain.
(use arrow to show movement)
H2O =
Salt =
We are only talking about the salt molecules and they will move from the [High] area to the [Low] area. So, the salt molecules on the right are in [High] (more crowded) and they will move to the left [Low] (less crowded).

7. Diffusion: Salt Movement
Slide 4
Diffusion: Salt Movement
Ex: Which way would the salt molecules move?
Explain.
(use arrow to show movement)
H2O =
Salt =
We are only talking about the salt molecules and they will not move right or left because there are 4 on each side making them equal.

8. Diffusion: Equilibrium
Slide 5
Diffusion: Equilibrium
H2O =
Salt =
When molecules are equal they are considered to be at equilibrium.
4 of each
4 of each 1 1 1 2
When molecules on both sides on the membrane (dotted line) are equal they are said to by in equilibrium. 1 2 2 2 3 3 3 3 4 4 4 4

9. Slide 6
Diffusion Movement
Kinetic E: The movement of molecules being diffused across a membrane.
The rate (speed) of this movement is determined by the temperature and the size of molecules.
Movement/diffusion of molecules, which is random, is called Kinetic E.
The movement/diffusion is dependent on the temperature and size of molecules.

10. Diffusion Movement Temperature Increasing the temp.
Slide 7
Diffusion Movement
Temperature
Increasing the temp.
Molecules diffuse faster
Decreasing the temp.
Molecules diffuse slower
Think of when you have liquid water and ice – the liquid water moves and has a higher temperature, but when you start to decrease the temperature and freeze it the movement slows and it becomes ice (a solid)

11. Diffusion Movement Size of molecules Smaller molecules
Slide 8
Diffusion Movement
Size of molecules
Smaller molecules
Molecules diffuse faster
Bigger molecules
Molecules diffuse slower
The smaller molecules can move across the membrane faster because they have less area to move across
The larger molecules move slowed across the membrane because they have move area to move across

12. Recap Diffusion Molecules move from [high] to [low]
Slide 9
Recap Diffusion
Molecules move from [high] to [low]
Equilibrium is when all particles on both sides are equal in number
Kinetic E causes them to move randomly
Temperature and Size changes rate of movement
^Recap^

13. Slide 10
Osmosis
Osmosis: The movement of water across a semipermeable membrane.
The most important thing here is that:
We are ONLY talking about the movement of WATER
Osmosis is just the movement of water, not other molecules.

14. Osmosis: Water Movement
Slide 11
Osmosis: Water Movement
Diffusion occurs from an area of high [water] (less solute) to an area of lower [water] (more solute)
Explain which way the
water molecules will move.
H2O:
Salt:
We are only talking about the water molecules and they will move from the [High] area to the [Low] area. So, the water molecules on the right are in [High] (more crowded) and they will move to the left [Low] (less crowded).

15. Direction of Osmosis Hypertonic
Slide 12
Direction of Osmosis
Hypertonic
Smaller amount of water outside the cell (more solute outside)
Water moves out of the cell
Cell shrinks
When talking about cells:
- When the amount of solute (dissolved particles) is higher outside the cell than inside the cell the water is at a [higher] inside and will move out

16. Cell in Hypertonic Solution
The Plasma Membrane
2/14/2019
Cell in Hypertonic Solution
15% NaCL 85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
copyright cmassengale
G. Podgorski, Biol. 1010

17. Direction of Osmosis Hypotonic
Slide 13
Direction of Osmosis
Hypotonic
Less water inside the cell (solute is higher)
Water moves in of the cell
Cell grows and can burst
When talking about cells:
- When the amount of solute (dissolved particles) is higher inside the cell than outside the cell the water is at a [lower] inside and will move in. This can result in the cell bursting open, like a water balloon getting too full.

18. Cell in Hypotonic Solution
The Plasma Membrane
2/14/2019
Cell in Hypotonic Solution
10% NaCL 90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
copyright cmassengale
G. Podgorski, Biol. 1010

19. Direction of Osmosis Isotonic
Slide 14
Direction of Osmosis
Isotonic
Water inside and outside the cell is equal
Water moves in and out of the cell equally
Cell stays the same
When talking about cells:
- When the amount of solute (dissolved particles) is equal inside and outside the cell then the water is at [equal] and will move in and out at the same rate continuously.

20. Cell in Isotonic Solution
The Plasma Membrane
2/14/2019
Cell in Isotonic Solution
10% NaCL 90% H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10% NaCL
90% H2O
What is the direction of water movement?
equilibrium
The cell is at _______________.
copyright cmassengale
G. Podgorski, Biol. 1010

21. copyright cmassengale
The Plasma Membrane
2/14/2019
Moves in/out
Moves in
Moves Out
Moves out
Moves in/out
Moves in
copyright cmassengale
G. Podgorski, Biol. 1010

23. Recap Osmosis Water molecules move from [high] to [low] Hypertonic:
Slide 15
Recap Osmosis
Water molecules move from [high] to [low]
Hypertonic:
Hypotonic:
Isotonic:
After hyper/hypo/iso-tonic the images of the cells with water movement was drawn.