Molecular Transport Vehicles
How can charged particles pass through the lipid membranes of cells? A model experiment with crown ethers shows one possible way.
The American feature film "Erin Brockovich" (2000) deals with one of the biggest environmental scandals in the United States in the 1990s. At that time, there was an extreme accumulation of cancer among residents of the Californian community of Hinkley. The culprit was apparently chromium-containing drinking water. As it turned out, PG&E (Pacific Gas & Electric) had been dumping chromate solutions into unlined effluent ponds for years, ending up in groundwater.
However, it was unclear at the time how the doubly negatively charged chromate ions, which are water-soluble but not fat-soluble, could pass through the lipid membrane of body cells and thus penetrate them. Today it is known that the cell membranes apparently have a mechanism to, for example, smuggle through the doubly negatively charged sulfate ion, which is essential for humans, by means of a carrier (carrier molecule). In the following we would like to understand this mechanism in two clear and quite simple model experiments.
The crown ethers accidentally discovered by Charles J. Pedersen in 1967 serve as carriers …
Membrane Transport Experiment Instructions
Model experiments on the passage of ions through a biomembrane
Download experiment instructions PDF (1.0 MB)