![]() On the surface, one of the most common, naturally-occurring phosphides is schreibersite, which doesn't come from below but from above in the form of meteorites. The Earth contains a lot of phosphide, but most of it is in the core, buried beneath 2,000 miles of rock. These molecules are typically combinations of phosphorus and metals, like the zinc phosphide found in rat poison or the iron-nickel phosphide called schreibersite. This extra reactivity could have helped phosphorus sneak its way into the game of life billions of years ago.Įxamples of reduced phosphorus compounds include phosphides. "Reduced phosphorus is more chemically reactive than phosphate," Pasek said. But other – more reduced - phosphorus compounds exist as well. The reason, Pasek explains, is that phosphate is the lowest energy state for P in our planet's oxygen-rich environment. Most of the phosphorus on the Earth's surface is found in some type of phosphate. The first life forms wouldn't have had anyone to sprinkle P-rich fertilizer on them, so where did they get their phosphorus from? #COSMIC VIEW CYCLE SOOTHE BUY FREE#Not satisfied with waiting for geological processes to free up phosphorus, humans currently spend a lot of effort mining "rock phosphate" and chemically modifying it to make fertilizer.Īnd there's the rub for astrobiologists. Indeed, the phosphorus cycle is one of the slowest element cycles of biological importance. Once the phosphorus is locked up in insoluble minerals, it takes a very long time for it to return to a form that plants and other organisms can use. There, it can be used by marine organisms, but eventually the phosphate settles on the seafloor where it becomes incorporated into rock sediments. Plants aren't able to recycle all of the available phosphorus in the soil, so some of it ends up going into the ocean through runoff. Plants pull out phosphorus compounds from the soil, but a lot of this is recycled material from decaying organic matter. Humans and other animals get their phosphorus from eating plants (or by eating animals that eat plants). Phosphorus also has an important role in vertebrates, whose bones and teeth contain apatite, a highly stable phosphate mineral.īecause of its vital role, all organisms on Earth must find a source of phosphorus. "The human body makes its weight in ATP each day and burns it," Pasek explains. Many biological functions require the energy from the breakdown (or burning) of ATP, which is often called the " molecular unit of currency" in energy transfer. It shows up three times in adenosine triphosphate, or ATP, which is a vital form of energy storage in cells. Phosphate plays other roles in the cell besides that in DNA. "The jury is still out over arsenate, but it's clear that phosphate is the best option when given a choice," Pasek said. Recently, a group of researchers claimed to have found a microbe that could use arsenate in place of phosphate, but controversy remains over this presumed discovery. Not many molecules could perform this three-charge juggling act. This overall charge helps to keep the molecule from drifting out of its proscribed location. Two of these oxygen atoms form ionic bonds with two neighboring sugars, while the third oxygen is left "dangling" with a negative charge that makes the whole DNA or RNA molecule negatively charged. The phosphate (PO 4) works as a kind of "super glue," since it has three oxygen atoms that will carry charges in solution. Both of these genetic molecules have a sugar-phosphate backbone. Phosphorus doesn't usually get as much attention as other essential nutrients like calcium and iron, but the element P shows up in a surprisingly wide range of biological molecules.įor starters, phosphorus is an important structural element in DNA and RNA. This research is supported by NASA's Exobiology and Evolutionary Biology program. Pasek is heading an effort to account for the possible chemical pathways that phosphorus could have taken to become available for life on the early Earth.
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