Osmosis: Concentration and Water
Osmosis Lab: Potatoes and Elodea
Background Information: Cells have a need to regulate their internal environment. They need to be able to this because cells often find themselves in environments where the concentration of dissolved solids outside the cell is different from the number of dissolved solids inside the cell. Since the solids can not move across the membrane, the cell responds by moving water either into or out of the cell in an attempt to balance the number dissolved particles. This process is called osmosis, the diffusion of water across a cell membrane.
So if a cell finds itself in an environment where there are a lot of dissolved particles outside compared to inside (a hypertonic environment), water will begin to flow from an area of high concentration inside the cell to an area of low concentration outside the cell. The cell will lose water (and mass), start to shrivel up and eventually die. This process is called plamolysis. It is the result of osmosis.
On the other hand, if the cell is in an environment where there are more dissolved particles inside the cell than outside (a hypotonic environment), water will diffuse into the cell across the membrane. The cell will swell up and eventually burst. This is also the result of osmosis.
An ideal environment is one where there is roughly the same number of dissolved particles inside the cell as outside (an isotonic environment). This is the environment that cells are normally found in and have adapted themselves to. In an isotonic environment the amount of water diffusing into a cell equals the amount of water diffusing out. The cell remains the same size and is a happy cell.
Hypertonic environments are more common than hypotonic ones for members of the bacteria, protists, fungi, and plants. Think about jelly. It sits in your refrigerator week after week without going bad. No mold, no bacterial colonies. Just jelly. You can’t do that with practically anything else. The reason
Background Information: Cells have a need to regulate their internal environment. They need to be able to this because cells often find themselves in environments where the concentration of dissolved solids outside the cell is different from the number of dissolved solids inside the cell. Since the solids can not move across the membrane, the cell responds by moving water either into or out of the cell in an attempt to balance the number dissolved particles. This process is called osmosis, the diffusion of water across a cell membrane.
So if a cell finds itself in an environment where there are a lot of dissolved particles outside compared to inside (a hypertonic environment), water will begin to flow from an area of high concentration inside the cell to an area of low concentration outside the cell. The cell will lose water (and mass), start to shrivel up and eventually die. This process is called plamolysis. It is the result of osmosis.
On the other hand, if the cell is in an environment where there are more dissolved particles inside the cell than outside (a hypotonic environment), water will diffuse into the cell across the membrane. The cell will swell up and eventually burst. This is also the result of osmosis.
An ideal environment is one where there is roughly the same number of dissolved particles inside the cell as outside (an isotonic environment). This is the environment that cells are normally found in and have adapted themselves to. In an isotonic environment the amount of water diffusing into a cell equals the amount of water diffusing out. The cell remains the same size and is a happy cell.
Hypertonic environments are more common than hypotonic ones for members of the bacteria, protists, fungi, and plants. Think about jelly. It sits in your refrigerator week after week without going bad. No mold, no bacterial colonies. Just jelly. You can’t do that with practically anything else. The reason