Photosynthesis
hidePhotosynthesis[α] is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea. Photosynthetic organisms are called photoautotrophs, since it allows them to create their own food. In plants, algae and cyanobacteria photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food.[β] The amount of energy trapped by photosynthesis is immense, approximately 100 terawatts: which is about six times larger than the power consumption of human civilization. As well as energy, photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100,000,000,000 tonnes of carbon into biomass per year.
Although photosynthesis can occur in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane. Some of the light energy gathered by chlorophylls is stored in the form of adenosine triphosphate (ATP). The rest of the energy is used to remove electrons from a substance such as water. These electrons are then used in the reactions that turn carbon dioxide into organic compounds. In plants, algae and cyanobacteria this is done by a sequence of reactions called the Calvin cycle, but different sets of reactions are found in some bacteria, such as the reverse Krebs cycle in Chlorobium. Many photosynthetic organisms have adaptations that concentrate or store carbon dioxide. This helps reduce a wasteful process called photorespiration that can consume part of the sugar produced during photosynthesis.
Photosynthesis evolved early in the evolutionary history of life, when all forms of life on Earth were microorganisms and the atmosphere had much more carbon dioxide. The first photosynthetic organisms probably evolved about 3,500 million years ago, and used hydrogen or hydrogen sulfide as sources of electrons, rather than water. Cyanobacteria appeared later, around 3,000 million years ago, and changed the Earth forever when they began to oxygenate the atmosphere, beginning about 2,400 million years ago. This new atmosphere allowed the evolution of complex life such as protists. Eventually, about 550 million years ago, one of these protists formed a symbiotic relationship with a cyanobacterium, producing the ancestor of the plants and algae. The chloroplasts in modern plants are the descendants of these ancient symbiotic cyanobacteria.
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News tagged with photosynthesis
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Nov 17, 2009 |
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(PhysOrg.com) -- Current atmospheric ozone levels are already suppressing soybean yields, according to Agricultural Research Service (ARS) scientists and university cooperators studying the effect of global ...
Genome Engineering Could Provide New Method of Creating Diesel
Nov 16, 2009 |
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When we think of genetic engineering, our minds often jump to giant tomatoes and animal cloning. However, this is not always the case.
Researchers turn algae into high-temperature hydrogen source
Nov 12, 2009 |
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In the quest to make hydrogen as a clean alternative fuel source, researchers have been stymied about how to create usable hydrogen that is clean and sustainable without relying on an intensive, high-energy ...
Toward home-brewed electricity with 'personalized solar energy'
Nov 04, 2009 |
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New scientific discoveries are moving society toward the era of "personalized solar energy," in which the focus of electricity production shifts from huge central generating stations to individuals in their ...
Mapping nutrient distributions over the Atlantic Ocean
Space & Earth / Earth Sciences
Nov 03, 2009 |
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Large-scale distributions of two important nutrient pools - dissolved organic nitrogen and dissolved organic phosphorus (DON and DOP) have been systematically mapped for the first time over the Atlantic Ocean in a study led ...
Iron controls patterns of nitrogen fixation in the Atlantic
Space & Earth / Earth Sciences
Nov 02, 2009 |
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Scientists including researchers from the National Oceanography Centre, Southampton and the University of Essex have discovered that interactions between iron supply, transported through the atmosphere from ...
Ancient ocean chemistry: Effects of biological oxygen production 100 million years before it accumulated in atmosphere
Space & Earth / Earth Sciences
Oct 29, 2009 |
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(PhysOrg.com) -- Scientists widely accept that around 2.4 billion years ago, the Earth's atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the "Great Oxidation Event" (GOE), the ...
Research May Help Plants, Humans Survive Stress, Disease
Oct 27, 2009 |
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(PhysOrg.com) -- New technology to analyze gene expression at the level of different cell types offers new insights in the ways that plants and animals react to the environment and how they change when they ...
Scientist increase the efficiency of a type of solar cell by incorporating ionic salts
Nanotechnology / Nanomaterials
Oct 14, 2009 |
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A group of scientists are working on the optimisation of a type of photovoltaic cell (Grätzel cell) that artificially mimics photosynthesis.
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Oct 07, 2009 |
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The many environmental issues facing our society are prevalent in the media lately. Global warming, rainforest devastation, and endangered species have taken center stage. Our ecosystem is composed of a very delicate network ...
Corals 'could starve in high CO2'
Oct 05, 2009 |
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(PhysOrg.com) -- As human activity pumps more and more carbon into the atmosphere, a new threat has emerged to the world's coral reefs - starvation.
Why leave it to nature? Chemistry professor wants to understand, simplify, photosynthesis
Sep 30, 2009 |
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(PhysOrg.com) -- Amid calls for transformative change in the world’s energy supply, Harvard chemist Ted Betley is taking a back-to-basics approach and examining the mother of all energy supplies -- photosynthesis ...
Light, photosynthesis help bacteria invade fresh produce
Sep 28, 2009 |
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Exposure to light and possibly photosynthesis itself could be helping disease-causing bacteria to be internalized by lettuce leaves, making them impervious to washing, according to research published in the October issue ...
New Drake equation to quantify habitability?
Space & Earth / Space Exploration
Sep 17, 2009 |
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Researchers from the Open University are laying the groundwork for a new equation that could mathematically quantify a habitat's potential for hosting life, in a similar way to how the Drake equation estimates ...
Scientists hone technique to safeguard water supplies
Aug 28, 2009 |
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A method to detect contaminants in municipal water supplies has undergone further refinements by two Oak Ridge National Laboratory researchers whose findings are published on line in Water Environment Research.
