DIFFUSION AND OSMOSIS

DIFFUSION is the movement of liquid or a gas molecules from a high concentration to a low concentration until the substance is evenly spread. important as it lets food and oxygen into a cell and waste products such as carbon dioxide out of the cell

MOLECULES IN SOLUTION TEND TO SLOWLY SPREAD APART OVER TIME. THIS IS DIFFUSION. How does a scent spread through a gas?

How Does a Dye Spread Through a Liquid?

How Does Heat Effect the Spread of Dye Through a Liquid?

OSMOSIS osmosis is the movement of water molecules, from a region of high water concentration to a region of low water concentration across a selectively permeable membrane.

SELECTIVELY PERMEABLE a membrane controls what goes in and out of the cell. permeable means it allows substances to go through it. a selectively permeable membrane is a membrane with holes in it small enough for water to go through it easily. big molecules like starch can not fit through easily

Model of a Selectively Permeable Membrane Water Starch Small molecules, such as water can pass through it. Large molecules like starch cannot pass through the membrane

Lots of water molecules Few water molecules Water Starch The water molecules pass both ways through the membrane The overall flow of water molecules is from a region with lots of water molecules to region of less water molecules. Until both sides have an evenly balanced water concentration. Osmosis – what will happen?

WHICH MOLECULES WILL DIFFUSE IN EACH OF THE FIGURES BELOW?

ANSWERS No Movement

SUMMARY osmosis is the movement of water molecules across a selectively permeable membrane. the membrane only allows small molecules to pass through it, large molecules can not pass through the membrane. water molecules move into the region where there are less water molecules the water acts to even up the concentration of water on either side of the membrane.

PLANT CELLS IN WATER in pure water – water will move in swelling the vacuole which pushes out against the cell wall. the cell does not burst because of the cell wall. Water moves Into the cell Plant cell placed in pure water

PLANT CELL IN STRONG SUGAR SOLUTION Strong Sugar/Salt Solution In a strong salt or sugar solution – water will move out of the vacuole causing it to shrink. The cytoplasm can also shrink away from the cell wall. The plant cell is described as flaccid.

ANIMAL CELLS IN DIFFERENT SOLUTIONS a red blood cell in pure water, water will move into the cell and the cell will burst (there is no cell wall to prevent this happening) in a strong salt/sugar solution water will move out and the cell will shrink