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In a reversal of the pattern on land, in the oceans, almost all photosynthesis is performed by algae and cyanobacteria, with a small fraction contributed by vascular plants and other groups. Algae encompass a diverse range of organisms, ranging from single floating cells to attached seaweeds. They include photoautotrophs from a variety of groups.
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
In red light, this is replaced by blue colored phycocyanin, which absorbs red light better. This reversible process is known as complementary chromatic adaptation. It is the component of photosynthetic system of cyanobacteria, as a particle with which various structures are linked (i.e. thylakoid membrane, etc.).
Photoautotrophs are organisms that can utilize light energy from sunlight and elements (such as carbon) from inorganic compounds to produce organic materials needed to sustain their own metabolism (i.e. autotrophy). Such biological activities are known as photosynthesis, and examples of such organisms include plants, algae and cyanobacteria.
In intense light, plants use various mechanisms to prevent damage to their photosystems. They are able to release some light energy as heat, but the excess light can also produce reactive oxygen species. While some of these can be detoxified by antioxidants, the remaining oxygen species will be detrimental to the photosystems of the plant. More ...
The eyespot apparatus (or stigma) is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids. It allows the cells to sense light direction and intensity and respond to it, prompting the organism to either swim towards the light (positive phototaxis ...
Algae that are carried passively by water are plankton, specifically phytoplankton. Algae constitute a polyphyletic group [4] since they do not include a common ancestor, and although their chlorophyll-bearing plastids seem to have a single origin (from symbiogenesis with cyanobacteria), [5] they were acquired in
Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria.