Diffusion & Active Transport

Review of cell membrane Controls what gets in and out of the cell. Semipermeable.

Concentration Amount of a substance compared to water High Concentration = A LOT of substance Low Concentration = SMALL amount of substance

High  Low Concentration diffusion Diffusion Does not use energy. Smaller molecules. High  Low Concentration Molecules move from areas where there is A LOT of the substance to areas where there is LESS of it. Examples: Water, Glucose, Oxygen, Carbon Dioxide, Iodine

diffusion

Low  High Concentration Active transport Active Transport Uses energy. Larger molecules. Low  High Concentration Molecules are very large and need the help of energy (ATP) to move across membrane. Move from areas where there is a SMALL AMOUNT of a substance to areas where there is MORE of it. Examples: Starch

Active transport

Diffusion Active Transport Two types of Transport Does not use energy. Smaller molecules. High  Low Concentration Active Transport Uses energy. Larger molecules. Low  High Concentration Brainpop

Diffusion of water If the amounts are not equal, but molecule is too large to pass through the membrane, WATER WILL DIFFUSE THROUGH THE MEMBRANE.

Osmosis: The Diffusion of water Animation Large Molecules

Osmosis: the Diffusion of water

Cells have some salt in them Place cell in pure, “distilled” water  WATER WILL ENTER THE CELL Place cell in salt water  WATER WILL LEAVE THE CELL

Water Diffuses into Cell Animation No diffusion of water Water Diffuses into Cell Water Diffuses out of Cell