Photosynthesis is one of the most important chemical processes on Earth. (Image credit: shutterstock)
One of the most well-studied chemical processes in nature, photosynthesis, may not work the way we thought, scientists have accidentally discovered.
Photosynthesis is the process by which plants, algae, and some bacteria convert carbon dioxide and water into oxygen and sugars for use as energy. To do this, the organisms use sunlight to oxidize, or take electrons from, water; and reduce, or give electrons to, carbon dioxide molecules. These chemical reactions require the photosystem the protein complex that contains chlorophyll, a pigment that absorbs light and gives plant leaves and algae their green color to transfer electrons between different molecules. For.
In the new study, published March 22 in the journal Nature (Opens in new tab), the researchers used a new technique, known as ultrafast transient absorption spectroscopy, to study how photosynthesis first occurs on a timescale of a quadrature of a second (0.0000000000000001 seconds) But how does it work? The team was initially trying to find out how quinones ring-shaped molecules that can steal electrons during chemical processes affect photosynthesis. But instead, the researchers found that electrons may have been released from the photosystem much earlier during photosynthesis than scientists had previously believed.
“We thought we were just using a new technique to confirm what we already knew,” said the co-author. jenny zhang (Opens in new tab), a biochemist specializing in photosynthesis at the University of Cambridge in England, said in a statement (Opens in new tab). “Instead, we found a new pathway, and opened the black box of photosynthesis a little further.”
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Photosynthetic algae viewed under a microscope. Their green color is a result of the pigment chlorophyll found inside the photosystem. (Image credit: shutterstock)
Two photosystems are used during photosynthesis: photosystem I (PSI) and photosystem II (PSII). PSII primarily provides electrons to PSI by taking them from water molecules: PSI then excites the electrons before releasing them and ultimately giving carbon dioxide to form sugars, through a series of complex steps. .
Previous research suggested that the protein scaffolding in PSI and PSII was very thick, which helped keep electrons within them where they were needed. But new ultrafast spectroscopy techniques showed that the protein scaffolding was more “leaky” than expected and that some electrons could be absorbed by chlorophyll within the photosystem almost immediately after light from the photosystem was absorbed. So these electrons can reach their destination faster than expected.
“The new electron transfer pathway we found here is completely surprising,” Zhang said. “We don’t know as much about photosynthesis as we thought.”
Electron leaking was observed both in isolated photosystems and within “living” photosystems inside cyanobacteria.
In addition to rewriting what we know about photosynthesis, the discovery opens up new avenues for future research and biotechnological applications. The team believes that by “hacking” photosynthesis to release these electrons at earlier stages, the process could be more efficient, which could help to make plants more resistant to sunlight or to combat can be artificially replicated to create renewable energy sources to help Climate change, according to the statement. However, more research is needed before this can happen.
“Many scientists have tried to extract electrons from an earlier point in photosynthesis, but said it was not possible because the energy is so buried in the protein scaffold,” Zhang said. “The fact that we can [potentially] To steal them earlier in the process is mind-blowing.”
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