Cell transport

Essay by thejoounitHigh School, 11th gradeA+, June 2007

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Cells get things they need inside themselves by transport across their cell membrane. Three types of transport are osmosis, facilitated diffusion, and endocytosis/exocytosis.

Osmosis is how cells obtain water, which is what cells are mostly made of. Osmosis is the net movement of water molecules across the cell membrane from high concentration to low concentration or with the gradient. This method doesn’t require energy. Water molecules are extremely tiny; they are only made up of three atoms, which is why they easily pass through the cells semi permeable membrane. They slip right between the membranes phospholipid bi-layer. Osmosis is driven by solute concentrations on the outside of the cell as well as the inside of the cell. Water molecules move from areas of high concentration to low concentration, so it will move to an area with a higher concentration of solute. Water will move until the concentrations on the outside and inside of the cell are equal and create an equilibrium, in which there is no net movement of water.

If a cells solution is isotonic to the outside solution there will be no net movement of water, this means that the two solutions have equal concentrations of water and solute. If a cells solution is hypertonic to its outside water will flow into the cell, which could cause it to burst. This means that the cell had a higher solute concentration and water had to flow in to try to dilute it. If a cell is hypotonic to the solution it is in the water will flow out. This means that the solution outside the cell had a high solute concentration. Osmosis is very important for all cells; it is how cells obtain most of their water. In plant cells, osmosis can cause the cell to swell, the...