A Toxic Substance---Alcohol

Why is alcohol a toxic, or hazardous, substance?

Alcohol is attracted to cell membranes, and it concentrates there. When it reaches nerve cell membranes, the alcohol can change the function of nerve cells and thus affect behavior. This change in behavior is commonly called intoxication.

How does alcohol affect cell membranes?

At one time, scientists believed that alcohol "dissolved" into the membrane interior and made the carbon chains of the lipids more fluid. (It was thought to be like converting hard butter into soft margarine.) 

When scientists tested this idea on fish, they realized that the "melted butter" idea could not explain intoxication. Warming fish by a few degrees can cause the same degree of lipid "melting", but the fish do NOT get intoxicated. 

So what causes intoxication?

The answer can be answered in part from the chemistry of alcohol (CH₃CHOH). The carbon part of the molecule makes it attracted to the carbon tails of the lipids in cell membranes. But the OH group of alcohol makes it attracted to water.

Thus, you might expect that these influences would cause alcohol to orient itself in a membrane so that the carbon part of the molecule inserts itself into the membrane interior (where the lipid carbon tails are) and the OH part of the molecule is out near the surface, where the water is. This idea has been recently confirmed by the author of Cells Are Us and his colleagues here at Texas A&M.