Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", σύνθεσις, synthesis, "putting together". In most cases, oxygen is released as a waste product. Most plants, most algae, cyanobacteria perform photosynthesis. Photosynthesis is responsible for producing and maintaining the oxygen content of the Earth's atmosphere, supplies all of the organic compounds and most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane.
In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting of water is used in the creation of two further compounds that serve as short-term stores of energy, enabling its transfer to drive other reactions: these compounds are reduced nicotinamide adenine dinucleotide phosphate and adenosine triphosphate, the "energy currency" of cells. In plants and cyanobacteria, long-term energy storage in the form of sugars is produced by a subsequent sequence of light-independent reactions called the Calvin cycle. In the Calvin cycle, atmospheric carbon dioxide is incorporated into existing organic carbon compounds, such as ribulose bisphosphate. Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are reduced and removed to form further carbohydrates, such as glucose; the first photosynthetic organisms evolved early in the evolutionary history of life and most used reducing agents such as hydrogen or hydrogen sulfide, rather than water, as sources of electrons.
Cyanobacteria appeared later. Today, the average rate of energy capture by photosynthesis globally is 130 terawatts, about eight times the current power consumption of human civilization. Photosynthetic organisms convert around 100–115 billion tons of carbon into biomass per year. Photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis. In plants and cyanobacteria, photosynthesis releases oxygen; this is called oxygenic photosynthesis and is by far the most common type of photosynthesis used by living organisms. Although there are some differences between oxygenic photosynthesis in plants and cyanobacteria, the overall process is quite similar in these organisms. There are many varieties of anoxygenic photosynthesis, used by certain types of bacteria, which consume carbon dioxide but do not release oxygen.
Carbon dioxide is converted into sugars in a process called carbon fixation. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrate, cellular respiration is the oxidation of carbohydrate or other nutrients to carbon dioxide. Nutrients used in cellular respiration include amino acids and fatty acids; these nutrients are oxidized to produce carbon dioxide and water, to release chemical energy to drive the organism's metabolism. Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments; the general equation for photosynthesis as first proposed by Cornelis van Niel is therefore: CO2carbondioxide + 2H2Aelectron donor + photonslight energy → carbohydrate + 2Aoxidizedelectrondonor + H2OwaterSince water is used as the electron donor in oxygenic photosynthesis, the equation for this process is: CO2carbondioxide + 2H2Owater + photonslight energy → carbohydrate + O2oxygen + H2OwaterThis equation emphasizes that water is both a reactant in the light-dependent reaction and a product of the light-independent reaction, but canceling n water molecules from each side gives the net equation: CO2carbondioxide + H2O water + photonslight energy → carbohydrate + O2 oxygen Other processes substitute other compounds for water in the electron-supply role.
In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide
The 2014–15 Stuttgarter Kickers season is the 115th season in the club's football history. In 3. Liga the club plays in the 3. Liga, the third tier of German football; the club plays in the DFB-Pokal, it is the club's first season back in the DFB-Pokal since 2006. The club takes part in the 2014–15 edition of the Württemberg Cup. Win Draw Loss Postponed 1.^ Times in Central European Time/Central European Summer Time 2.^ Kickers goals listed first. Win Draw Loss Win Draw Loss Amar Cekic and Daniel Lang had no professional contract, they played at Stuttgarter Kickers II. Kickers' reserve team played in the Oberliga Baden-Württemberg and the coach was Jürgen Hartmann. Note: Flags indicate national team as defined under FIFA eligibility rules. Players may hold more than one non-FIFA nationality. 3.^ Redl, Fennell, Baumgärtel, Marchese, Braun, G. Müller, Edwini-Bonsu, Calamita 7.^ Redl, Fennell, Baumgärtel, Marchese, Braun, G. Müller, Edwini-Bonsu 2014-15 Stuttgarter Kickers season at Kickersarchiv.de 2014–15 Stuttgarter Kickers season at Weltfussball.de 2014–15 Stuttgarter Kickers season at kicker.de 2014–15 Stuttgarter Kickers season at Fussballdaten.de
Neeru Khosla is the co-founder and chair of the non-profit CK12 Foundation. Having grown up in India and England, Khosla wanted to be a doctor, she had an aptitude for science, but the prerequisite for medicine of animal dissection pushed her to pursue microbiology instead. Khosla focused her studies in India on science and moved to the U. S. shortly after marrying Vinod Khosla in 1980. Around the time he co-founded Sun Microsystems, she earned a master's degree in molecular biology from San Jose State University. Soon, she started a job studying gene expression at Stanford University, she has a master's degree in education from the Stanford Graduate School of Education. In December 2008, it was announced that Khosla had been appointed to the Wikimedia Foundation advisory board, she has been on the boards of other organizations including the American India Foundation and DonorsChoose. She is married to the billionaire engineer and venture capitalist Vinod Khosla, her "childhood boyfriend", they have four children.
O'Reilly TOC Conference 2008 Neeru Khosla on Education and Doing a Start-Up