The use of oral rehydration solutions (ORS) in the treatment of diarrhoeal diseases. The applications and implications of science in developing improved oral rehydration solutions; ethical issues associated with trialling improved oral rehydration solutions on humans.

Diarrhoea leaves people dehydrated and with depleted amounts of necessary salts, as these things are lost in faeces. Cholera is an example of an illness that causes diarrhoea.

Oral rehydration solutions (ORS) are used to rehydrate and replenish key molecules.

ORS is a mixture of water, salts and sugars. A simplified ration is 1 litre of water to six teaspoons of sugar to half a teaspoon of salt. The water is often boiled to sterilise it.

• Sodium is needed because it goes into the cells and brings the water potential back down, this means water will move by osmosis back into the cells, and from there into the blood.
• Sodium has to enter the cells through co-transportation (because the normal carrier proteins are pumping sodium out) with glucose- this means that glucose is also needed.
• Other salts that make ORS isotonic; so that when people are drinking it their cells do not absorb all of the water and burst.

To work out the right proportions of salts and liquids, a lot of testing had to be done. This involved trialling early mixtures on humans to note the side effects and make appropriate changes. In the process many peoples conditions were worsened due to having too much of a certain molecule: too much glucose in one trial resulted in more water being drawn into the intestine and the diarrhoea was worsened.

Some claim that it is immoral to jeopardise peoples health by giving them un-trialled solutions; however, by trying out the solutions on people, scientists were able to refine ORS to create an effective treatment that saves many lives.

The specification wants you to say it contains glucose and:
Sodium (ions) / potassium (ions) / chloride (ions) / citrate (ions);