Addiction is a complex physiological phenomenon. And smoking is among the most difficult habits to kick. Nicotine affects tiny protein 'tunnels' – known as ion channels – in the membranes of our nerve cells, producing a combination of stimulant and relaxant effects on the body. By binding to specific channels, it causes them to swing open, allowing ions (molecular messengers) to flow into the cell. This triggers the production of neurotransmitters including acetylcholine. Acetylcholine acts on another channel simultaneously prompting contraction of skeletal muscle and relaxation of heart. Similar channels are found in the cells of animals, plants and even bacteria. Pictured above is a computer simulation of a channel from the bacterium Erwinia chrysanthemi. Reconstructed from crystallography experiments the image shows how individual atoms are arranged in the protein. Being simpler than its human counterpart the bacterial channel provides a model system to better understand how these channels work.
Written by Kat Arney
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.