Osmosis Coursework

Topics: Osmosis, Concentration, Cell wall Pages: 11 (4095 words) Published: February 12, 2013

Osmosis is defined as the net movement of water or any other solutions molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with all areas having an equal concentration.For this particular investigation I think that the lower the concentration of the salt solution in the test tube, the larger the increase in mass of the potato chip will be. This is because the water molecules pass from a high concentration. Therefore, I believe that the chips that are in the tubes containing a higher concentration of water than salt will have a larger mass than chips in tubes with higher salt concentrations. As shown bellow osmosis

Osmosis in PlantsPlants depend on osmosis to move water from their roots to their leaves. Osmosis is also crucial in plants as it protects leaves against losing water through evaporation.In osmosis in plants there are specialized cells called Guard cells which are all along the surface of the leaves. Each pair of guard cells surrounds a stoma or pore, controlling its ability to open to release water. Factors effecting rate of osmosisOsmotic pressureOsmotic pressure is the pressure caused by the difference of solute concentration between solutions separated by a semi-permeable membrane. As osmosis takes place pressure builds up on the side of the membrane where the solvent concentration has increased. This pressure prevents more water from entering the membrane and osmosis stops.PermeabilityPermeability affects the rate of osmosis because if a material is permeable it can allow molecules to pass through quicker than semi-permeable materials as the holes are bigger and can allow more molecules to pass through.

Hypotonic condition – When a plant cell is placed in a solution containing lower amount of solute and a higher concentration of water the cell swells up due to the movement of water into the cell. The cell becomes turgid and the rigid cell wall tries to hold this excess amount of water. Isotonic condition – When the plant cell is placed in a solution of similar concentration, water moves across the cell membrane in both the directions. The net movement of water is zero with no change in the cell size.

Hypertonic solution – When the plant cell is placed in a solution containing higher amount of solute and a lower concentration of water the cell shrinks as greater amount of water leaves the cell. The vacuole shrinks and the cytoplasm gets peeled off from the cell wall. Such cell is known as plasmolysed cell.

As shown bellow the effect of Osmosis in plant cell.

Osmosis in Animal cells
Animal cells have a no cell wall to stop them from swelling up. So if animal cells are placed in pure water they take in water by osmosis until the eventually burst. All animal cells have cytoplasm and a cell surface membrane which completely surrounds the cell. Most animal cells also have a nucleus. Red blood cells, however, are unusual and do not have a nucleus. As shown bellow the effect of Osmosis in Animal cells.

Factors that affect osmosis:
What affects the rate of osmosis:There are many factors that can affect the rate of osmosis; these are concentrations of solutions in osmosis, the surface area, temperature, distance, time, pressure, light and dark. Temperature: A faster temperature means a faster rate of reaction. Concentration: Water potential level in osmosis molecules have to move from an area of high water potential to an area of low water potential. Also the are of low water potential will contain more salt...
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