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Passive Transport - Diffusion and Osmosis



Osmosis occurring in a cell

What is (definition)

Passive transport is the transport that occurs between two solutions with different solute concentrations, which aims to equalize the concentrations, making them isotonic. This process occurs without the waste of energy. It is divided into two types: diffusion and osmosis.

How diffusion occurs (summary)

Diffusion is the passive mode of transport in which the solute moves from the more concentrated (hypertonic) to the less concentrated (hypotonic) solution. This is for the purpose of their becoming equal (isotonic) in terms of solute concentration.

Transport Speed ​​and Examples

The greater the difference between concentrations, the faster the transport will be. For example, nicotine enters the non-smoker's bloodstream faster than the smoker's, this is because this substance is not present in the non-smoker's bloodstream.

Another example about diffusion is chlorine thrown into the pool. It will completely mix the water, moving from the highest to the least concentrated medium until it is evenly distributed throughout the pool.

Osmosis and examples

Osmosis is the mode of passive transport in which the solvent (water, for example) is transporting through a semipermeable membrane from the lowest concentration medium (hypotonic solution) to the more concentrated medium (hypertonic).

A very simple example to understand osmosis is to observe the action of sugar on strawberry. When placed in contact with the strawberry, sugar receives the water contained in this fruit.

We also observe osmosis when bathing in the sea, since there is a much higher concentration of solute (salt) in the sea than that present in our body.

Simultaneous diffusion and osmosis

There are situations in which both (osmosis and diffusion) occur simultaneously. This is the case of salt that, when it goes into the bloodstream, will pass into the interstitial fluid (liquid from which cells draw their nutrients and deposit their waste) by diffusion. And by osmosis, the water contained in the interstitial fluid will pass into the bloodstream. The result will be increased blood volume and blood pressure.