lpetrich
Contributor
Caffeine is a favorite stimulant regularly used by large numbers of people.
It is a "purine", chemically similar to nucleobases adenine and guanine, and it works by blocking adenosine (adenine + ribose) from a certain receptor because of its chemical resemblance. That blocking increases the production of the neurotransmitter acetylcholine, thus the stimulant effect.
It is an Alkaloid a catch-all category of nitrogen-containing compounds produced by a great variety of organisms.
Caffeine is made from guanine with a few biochemical steps, and it is made by a variety of plants.
Eudicots
Returning to caffeine, its synthesis originated several times, widely scattered over the family tree of eudicot flowering plants.
But why might it be rare? The theory I've come up with is the Kill the Winner hypothesis - if a lot of plants make caffeine, then the bugs that eat them would have a lot of selection pressure to develop caffeine resistance. But if only a few plants make caffeine, then there is much less pressure on the bugs to become resistant. That same hypothesis also works for all the others, explaining their relative rarity.
More generally, "Kill the Winner" explains biodiversity - a big success would become a victim of its success by presenting a big target for disease organisms.
"Kill the Winner" also explains the multitude of histocompatibility surface-protein variants. These proteins are used to recognize fellow cells of a multicelled organism, and a bug (general, informal sense) can fake that recognition by having a surface with a similar protein. A multitude of h-c surface proteins can limit the success of that strategy.
That has the side effect of organ-transplant rejection, but what helps us reject transplants is what keeps us from being too big a target for infectious bugs.
It is a "purine", chemically similar to nucleobases adenine and guanine, and it works by blocking adenosine (adenine + ribose) from a certain receptor because of its chemical resemblance. That blocking increases the production of the neurotransmitter acetylcholine, thus the stimulant effect.
It is an Alkaloid a catch-all category of nitrogen-containing compounds produced by a great variety of organisms.
Caffeine is made from guanine with a few biochemical steps, and it is made by a variety of plants.
Eudicots
- Rosids - Eurosids - Malvids
- Malvales - Malvaceae
- Theobroma cacao -- cocoa/cacao tree
- Cola spp. -- kola-nut tree
- Sapindales - Sapindaceae - Paullinia cupana -- guaraná climbing plant
- Malvales - Malvaceae
- Asterids
- Euasterids
- Lamiids - Gentianales - Rubiaceae - Coffea arabica, canephora -- coffee tree
- Campanulids - Aquifoliales - Aquifoliaceae - Ilex vomitoria (yaupon), guayusa, paraguariensis (yerba maté) -- holly tree
- Ericales - Theaceae - Camellia sinensis -- tea tree
- Euasterids
Returning to caffeine, its synthesis originated several times, widely scattered over the family tree of eudicot flowering plants.
But why might it be rare? The theory I've come up with is the Kill the Winner hypothesis - if a lot of plants make caffeine, then the bugs that eat them would have a lot of selection pressure to develop caffeine resistance. But if only a few plants make caffeine, then there is much less pressure on the bugs to become resistant. That same hypothesis also works for all the others, explaining their relative rarity.
More generally, "Kill the Winner" explains biodiversity - a big success would become a victim of its success by presenting a big target for disease organisms.
"Kill the Winner" also explains the multitude of histocompatibility surface-protein variants. These proteins are used to recognize fellow cells of a multicelled organism, and a bug (general, informal sense) can fake that recognition by having a surface with a similar protein. A multitude of h-c surface proteins can limit the success of that strategy.
That has the side effect of organ-transplant rejection, but what helps us reject transplants is what keeps us from being too big a target for infectious bugs.