Type of Passive Transport

Posted: March 24, 2011 in Uncategorized

Passive Transport

  • simple diffusion
  • osmosis
  • facilitated diffusion

~Simple Diffusion~

1. Diffusion is the movement of molecules in air or in solution from a region of high concentration to a region of low concentration.

2. Oxygen in the inspired air must diffuse across the membrane of the alveoli and the wall of the capillaries before it gets into the blood. Oxygen would then be transported to all the cells in the body by the circulatory system.

3. When oxygen reaches the cells, it has to diffuse across the capillary wall and the plasma membrane of the cells before it can enter the cells.

4.Conversely, CO2 that is produced by the cells diffuses out into the blood circulation that transport it to the lungs. There, CO2 diffuses from the capillaries into the lungs and is expelled out.

 

~Osmosis~

1. Osmosis is the movement of water from a region of low solute concentration to a region of high solute concentration.

2. eg.:  ~water absorption from the intestine

~water reabsorption from the kidney tubules

~water uptake from the soil by the root hairs

 

~Facilitated Diffusion~

1. Some substances cannot diffuse passively across the membrane because they are either insoluble in lipid or too big to pass through the pores.

2. Some molecules in the membrane can “carry” these substances across. These “carrier molecules” consist of membrane proteins.

3.The products of digestion such as glucose and amino acids have to cross the wall of the epithelial cells lining the intestine and the wall of the capillaries to get into the circulartory system.

4. These nutrients are lipid-insoluble and they are too large to pass through yhe pores in the membrane. Fortunately, some carrier proteins in the membrane are able to trap these nutrients and carry them across the membrane via facilitated diffusion.

5. This occur in almost all body cells, especially along the villi of the epithelial cells lining the small intestine. The nutrients are then distributed to all the cells in the body. On reaching the cells, the nutrients cross the capillary wall and the plasma membrane of the cells via facilitated diffusion.

 

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Comments
  1. peggielee95 says:

    thanks guys .. for the information about passive transport. I learned a lots ! =]

  2. 5 people says:

    Simple, easy to understand and COLOURFUL…

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