During thelight-dependent reactions, accumulate in the .

Combustion Reaction CHEMICAL REACTIONS Who?
This process occurs in:
- plants
- Algae
- Bacteria
-Some protists Where?
- Photosynthesis happens in the chloroplast of a cell.
- Photosynthesis produces energy for the organism.

Duringthe light-dependent reactions, water molecules are , producing ,, and .

usually convert light into with a of 3–6%. Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature and proportion of carbon dioxide in the atmosphere, and can vary from 0.1% to 8%. By comparison, convert light into at an efficiency of approximately 6–20% for mass-produced panels, and above 40% in laboratory devices.

Light-dependent reactions of photosynthesis - BioTopics

The twomain products of the light-dependent reactions are  and .A by-product is .

Although photosynthesis can happen 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 called that contain . In plants, these proteins are held inside called , while in bacteria they are embedded in the . Some of the light energy gathered by chlorophylls is stored in the form of (ATP). The rest of the energy is used to remove 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 , but different sets of reactions are found in some bacteria, such as the in . Many photosynthetic organisms have adaptations that concentrate or store carbon dioxide. This helps reduce a wasteful process called that can consume part of the sugar produced during photosynthesis.

Photosynthesis - Song with Free Worksheets and Activities

thought that a complex of reactions consisting of an intermediate to cytochrome b6 (now a plastoquinone), another is from cytochrome f to a step in the carbohydrate-generating mechanisms. These are linked by plastoquinone, which does require energy to reduce cytochrome f for it is a sufficient reductant. Further experiments to prove that the oxygen developed during the photosynthesis of green plants came from water, were performed by Hill in 1937 and 1939. He showed that isolated give off oxygen in the presence of unnatural reducing agents like , or after exposure to light. The Hill reaction is as follows:

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Robert Emerson discovered two light reactions by testing plant productivity using different wavelengths of light. With the red alone, the light reactions were suppressed. When blue and red were combined, the output was much more substantial. Thus, there were two photosystems, one absorbing up to 600 nm wavelengths, the other up to 700 nm. The former is known as PSII, the latter is PSI. PSI contains only chlorophyll a, PSII contains primarily chlorophyll a with most of the available chlorophyll b, among other pigment. These include phycobilins, which are the red and blue pigments of red and blue algae respectively, and fucoxanthol for brown algae and diatoms. The process is most productive when absorption of quanta are equal in both the PSII and PSI, assuring that input energy from the antenna complex is divided between the PSI and PSII system, which in turn powers the photochemistry.

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made key discoveries explaining the chemistry of photosynthesis. By studying and green bacteria he was the first scientist to demonstrate that photosynthesis is a light-dependent reaction, in which hydrogen reduces carbon dioxide.