Hopanoids

The hopanoids (stress on the penultimate vowel: hopanoids ) are membrane -enhancing molecules. They are extremely stable triterpenes and consist of four six-membered rings, a five-membered ring and residues of different chain length. They have thus a structural similarity to steroids.

Dissemination

In bacteria hopanoids used instead of steroids that occur in eukaryotes, as a membrane amplifier. Exceptions to this are the methanotrophic bacteria, which fall to the Proteobacteria, as well as the mycoplasmas, which are gram- positive bacteria. These have as eukaryotes steroids instead of hopanoids, but they can not synthesize itself, but take from the outside.

Hopanoids that are found in cyanobacteria, were found in stromatolites in 2.7 billion year old Australian rock layers, making them among the oldest examples of the internal structure used to living beings.

As far as is known, hopanoids not occur in archaea.

Swell

• J. Brocks, G. Logan, R. Buick, R. Summons: Archean molecular fossils and the early rise of eukaryotes. Science 285/5430/1999, pp. 1033-1036, PMID 10446042

• Terpene
• Substance Group