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 Molecule move down concentration gradients – C.G = Difference in concentration from 1 area to another Where is the high Oxygen concentration? Where is the high CARBON DIOXIDE concentration?

The woman inhales a breath of oxygen

The oxygen spreads into the womans lungs

The oxygen fills the air sacs (alveoli) located in her lungs

Where is the HIGH oxygen concentration? Where is the LOW oxygen concentration? Due to diffusion, the oxygen will spread from the area of high to the area of low concentration

The heart pumps this oxygen-rich blood around your body

Cell X needs oxygen just like all cells. But cell X is not in direct contact with the blood and oxygen. So how does cell X get oxygen?

Where is the HIGH oxygen concentration? Cell X (and all other cells) gets oxygen through the process of diffusion!

The reverse process is true w/ carbon dioxide. Over time, CO2 waste builds up in cells. Too much is fatal. It must be removed.

Where is the HIGH carbon dioxide concentration? CO2 diffuses from the cells (high concentration) and into the blood stream (low concentration)

The heart pumps the CO2 rich blood back to the lungs.

Where is the HIGH carbon dioxide concentration? CO2 diffuses into the air sacs (alveoli)

The diaphrag m muscle pushes the CO2 out of the lungs

CO2 is expelled from the woman…the process repeats with every breath!

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/shriveled. 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 Q: Why are the molecules exiting this cell and not entering? A: There are more molecules inside than out