HIV Treatments
HIV, of the Human Immunodeficiency Virus, affects just under 1% of the world's population. Spread through bodily fluids, this virus infects the important cells of your immune system. A weakened immune system can lead to life threatening infections and allow certain types of cancer to divide and grow unchecked. People with HIV-1 usually develop AIDS.
The virus enters your cells by attaching itself to a transport proteins in the cell membrane and uses that protein to inject its genetic material into the cell. New treatments have been developed to prevent this from happening. A drug called an inhibitor can bind to these transport proteins before the HIV virus does. This will slow the spread of the virus' genes (remember, virus can't multiply on their own....they can only infect human cells and "hope" for those cells to divide).
Without our knowledge of the different kinds of transport proteins in cell membranes and an understanding of how they work, this treatment would not have been possible! Now we are able to improve the quality of life (and prolong the lives of) numerous HIV suffers around the world.
Desalination
The world is currently facing a fresh water shortage and desalination is many countries' solution to this problem. As it were, we would not be living in Qatar if it weren't for desalination! There are two types of desalination. The first is thermal desalination where seawater is boiled and the evaporate (which is salt-less) is collected. This process is very energy intensive as water has a very high heat capacity (aka. it takes a lot of energy to heat it up even slightly). The second process, which is a fairly new technology, is called membrane desalination and, you guessed it, it uses a selectively permeable membrane.
Osmosis is a process where water will flow from a hypotonic solution to a hypertonic solution. This movement of water particles creates pressure (this is called osmotic pressure and it is a force that
pushes water particles across a membrane). In the membrane desalination process, scientists use this principal! They push water particles across a semi-permeable membrane thus separating it from the salt. The salt can't get through the membrane, it's too big!! So this process will be the opposite of osmosis... water will move from a hypertonic solution (salty seawater) to a hypotonic solution (pure drinking water) across a semi permeable membrane. Therefore, it's called
reverse osmosis. Heard of it before? If not, take a look at some of your bottled water and you'll find the word eventually! The reverse osmosis process is not just used in desalination, it's also used to purify any kinds of water with dissolved solutes.
Here's a diagram comparing osmosis (diagram on the left) and reverse osmosis used in desalination (diagram on the right).
Dialysis
Your kidneys are amazing at membrane transport. They rely heavily on diffusion in order to purify your blood and get rid of all those yucky wastes! Unfortunately some people's kidneys fail. If it were not for dialysis their blood would quickly reach toxic levels and result in death.
Simply, dialysis has two parts: a semi permeable membrane and dialysate, a fluid that has just the right concentration of solutes to allow the diffusion of appropriate molecules in appropriate concentrations. The patient's blood is removed from his/her body and filtered through a dialysis machine containing these two items. Particles in the blood flow across the membrane following a concentration gradient, and into the dialysate. This is simple diffusion! Clean blood is then returned to the patient's body.
Here is a simplified diagram of the dialysis process:
