how does the cell diffusiion occur in the cell ?

Asked by Saurabh Vyas | 11th Sep, 2010, 12:00: AM

Expert Answer:

There are two ways that the molecules move through the membrane: passive transport and active transport. Active transport requires that the cell use energy that it has obtained from food to move the molecules (or larger particles) through the cell membrane. Passive transport does not require such an energy expenditure, and occurs spontaneously.
The principle means of passive transport is diffusion. Diffusion is the movement of molecules from a region in which they are highly concentrated to a region in which they are less concentrated. It depends on the motion of the molecules and continues until the system in which the molecules are found reaches a state of equilibrium, which means that the molecules are randomly distributed throughout the system.

Diffusion can occur through a cell membrane. The membrane allows small molecules like water (H2O), oxygen (O2), carbon dioxide (CO2), and others to pass through easily. It is said to be permeable to these molecules. If a cell is floating in a water solution (like the ocean) that has some oxygen dissolved in it, the oxygen molecules will move into the cell. They will also move out of the cell at the same rate, and a dynamic equilibrium will exist. However, if the cell uses some of the oxygen as it comes into the cell, more oxygen will move into the cell than out of the cell.

So the oxygen effectively moves from a region of high concentration (the seawater) to a region of low concentration (the cell), and diffusion occurs. Likewise, as the chemical reactions in the cell use up oxygen they produce carbon dioxide. The concentration of carbon dioxide inside the cell increases so that more CO2 molecules strike the inside of the cell and move out than strike the outside of the cell and move in. So the overall effect is that the CO2 moves out of the cell.


Answered by  | 11th Sep, 2010, 11:31: PM

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