This image shows a secondary structural representation of liver alcohol dehydrogenase, an enzyme in the liver that converts ethyl alcohol into acetaldehyde. The catalyzed reaction involves the coenzyme NAD; this receives a hydrogen ion removed from an alcohol molecule bound elsewhere in the protein. This representation of LADH shows regions of alpha helix as regular spirals, and stretches of beta strand as arrows. These structural 'motifs' are joined by stretches of randomly coiled polypeptide chain. The catalytic domain, where the alcohol molecule is bound, is shown in shades of blue. The cofactor binding domain (where NAD is bound) is shown in shades of yellow. The cofactor NAD itself is shown in place in the cofactor binding site, in a 'stick' representation, coloured magenta. A version of this appeared in Scientific American recently.