"Life is a flame with a memory."
"the isotope record assures us that, however they came about, by the Archaean there were microbes on earth, their biochemistry capable of distinguishing between light and heavy carbon."
Where respiration, for example, has reduced sulphates to sulphides, photosynthesis can reverse the process. It can fill the biosphere with things that will react together, providing new opportunities for life–while, in the process, challenging it to regulate the now unbalanced world it finds itself in."
Acasta gneiss from Canada is only large remaining rock segments from the Hadean
"life maintains its inner order across cosmic spans of time."
"the bacteria are astonishingly good at finding energy that will let them make a living.
"This vast range of biochemical capabilities makes bacteria vital to the rest of life on earth."
"The endless stream of electrons running through these bacterial metabolisms provides the background hum of the earth's habitability."
"...the first photosystem was an adaptation of one of the protein way-stations on a bacterial electron transfer chain used in respiration."
pigments possibly absorb "ultraviolet light" "defences against ultraviolet light"
photosystem I is found in purple bacteria and some relatives
photosystem II is found in green sulphur bacteria
"only cyanobacteria have both types, sprung together into a Z-scheme
"It was within the context of cyanobacteria, however they evolved, that photosynthesis made its great leap forward, and finally learned to use water as an electron donor. This moved life beyond the potential limits that might be imposed by scarcity...."
"life has a non-negotiable need for water."
"the mystery of how the manganese cluster became incorporated into photosystem II is deeply intriguing and far from solved."
Photosystem II grew out of an earlier photosystem which shared its ancestry with a cytochrome."
[note: "A magnesium porphyrin complex is the heart of chlorophyll, the active molecule of photosynthesis. A magnesium porphyrin complex is the heart of chlorophyll, the active molecule of photosynthesis."
biologically important molecule porphyrin
"The porphyrins are actually an enormous group of organic compounds, found all over the living world. The special thing about porphyrins is that they bind metals. The four nitrogens in the middle of the porphyrin molecule act as teeth: they can grab and hold metal ions such as magnesium (Mg), iron (Fe), zinc (Zn), nickel (Ni), cobalt (Co), copper (Cu), and silver (Ag).
See also – http://www.ratbehavior.org/porphyrin.htm
"The Great Oxidation Event"
– 2.4 billion years ago
red (oxidized) sediments do not occur in the Archaean
rocks through out the Archaean have a full component of sulphur isotopes other wise unseen in an Oxygen enriched atmosphere.
oxidize means to remove a hydrogen from something
note: technically– undergo a reaction in which electrons are lost
oxidation of carbon ~> carbon dioxide
reduction of carbon ~> methane
 When a porphyrin molecule grabs a metal, it acquires different properties and gets a different name. So, if the central metal is iron (Fe), the porphyrin complex is called ferroporphyrin, or heme. Hemoglobin, the molecule in your red blood cells that grabs oxygen, has four of these heme groups. The iron ion of the heme group is responsible for binding the oxygen. The hemoglobin travels around the body, and when it reaches the tissues the iron in the porphyrin complex releases the oxygen to nourish them.
Chlorophyll, the all-important molecule that allows plants to capture the sun's energy, and is responsible for plants' green color, is made up in part of a porphyrin molecule whose central metal ion is magnesium (Mg). The vitamin B12 consists of a porphyrin molecule with a cobalt ion in the middle.
So, porphyrins are an extremely important group of organic compounds. They are universal, found in most living cells of animals and plants, where they perform a wide variety of functions.
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