Diffusion: Movement of molecules from an area of high to low concentration Movement continues until equilibrium is reached Equilibrium: same amount of molecules on the outside of a cell as the inside

Diffusion (contd) Passive transport: No energy (ATP) required to move molecules If more molecules outside the cell… they move inside (and vise versa) Where is the high Oxygen concentration? Where is the high CARBON DIOXIDE concentration?

Where is the HIGH oxygen concentration? Where is the LOW oxygen concentration?

Where is the HIGH oxygen concentration? Where is the LOW oxygen concentration? Cell X gets oxygen through the process of diffusion!

The reverse process is true w/ carbon dioxide.

Where is the HIGH carbon dioxide concentration?

Osmosis Defined: Diffusion of water from an area of high to low concentration High H 2 O concentration –Less solutes –Ex: Distilled water Low H 2 O concentration –More solutes –Ex: Salt water

Dots represent dissolved particles (not water molecules)

Group Explanation A cell has been placed into a mystery solution and appears to have shrunken. 1)What can you conclude about the water concentration inside the cells compared to outside? 2)What can you conclude about the solute concentration inside the cells compared to outside? 3)Which type of solution is the cell placed in? 4)Using your explanation of osmosis, explain why the cell appears to have shrunken.

A cell has been placed into a mystery solution and appears to have shrunken. 1) What can you conclude about the water concentration inside the cells compared to outside? This means there was a greater water concentration inside the cell and it lost water. 2) What can you conclude about the solute concentration inside the cells compared to outside? Because the water concentration was high (see question 1), there must have been a low amount of solutes inside the cell. 3) Which type of solution is the cell placed in? hypertonic 4) Using your explanation of osmosis, explain why the cell appears to have shrunken. The cell shrunk because it lost water. There was a greater water concentration inside the cell so therefore water diffused out of the cell.

Facilitated Diffusion Defined: Larger molecules enter/exit with the help of protein channels in the plasma membrane No energy is required (passive) Q: Why are the molecules exiting this cell and not entering? A: There are more molecules inside than out

Kobe Kuiz 1) In which direction does diffusion occur? 2) Across which part of the cell does diffusion mostly occur? 3) Which molecule of energy is not required during passive transport? 4) True or False: More solutes creates less concentrated water. 5) Which solution is involved in osmosis? 6) Examine the picture. If the dots are solutes, where is the high solute concentration? 7) Examine the picture. If the dots are water molecules, where is the low water concentration? 8) Examine the picture. If the dots are water molecules, which way will osmosis occur? 9) Examine the picture. If the dots are solute molecules, which way will osmosis occur?

Kobe Kuiz Answers 1)In which direction does diffusion occur?  From a high to low concentration 2)Across which part of the cell does diffusion mostly occur?  Cell membrane 3)Which molecule of energy is not required during passive transport?  ATP 4)True or False: More solutes creates less concentrated water.  True 5)Which solution is involved in osmosis?  water 6)Examine the picture. If the dots are solutes, where is the high solute concentration?  Left side 7)Examine the picture. If the dots are water molecules, where is the low water concentration?  Right side 8)Examine the picture. If the dots are water molecules, which way will osmosis occur?  From left t(high concentration) to right (low concentration) 9)Examine the picture. If the dots are solute molecules, which way will osmosis occur?  From right (high water concentration) to left (low water concentration)