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Photosynthesis usually refers to oxygenic photosynthesis, a process that produces oxygen. Photosynthetic organisms store the chemical energy so produced within intracellular organic compounds (compounds containing carbon) like sugars, glycogen , cellulose and starches .
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. [1] They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.
The Type II photosynthetic apparatus in non-oxygenic bacteria consists of light-harvesting protein-pigment complexes LH1 and LH2, which use carotenoid and bacteriochlorophyll as primary donors. [3] LH1 acts as the energy collection hub, temporarily storing it before its transfer to the photosynthetic reaction centre (RC). [ 4 ]
Organisms that contain bacteriochlorophyll conduct photosynthesis to sustain their energy requirements, but the process is anoxygenic and does not produce oxygen as a byproduct. They use wavelengths of light not absorbed by plants or cyanobacteria. Replacement of Mg 2+ with protons gives bacteriophaeophytin (BPh), the phaeophytin form.
In general, photosynthesis in cyanobacteria uses water as an electron donor and produces oxygen as a byproduct, though some may also use hydrogen sulfide [84] a process which occurs among other photosynthetic bacteria such as the purple sulfur bacteria. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle. [85]
A photosynthetic pigment (accessory pigment; chloroplast pigment; antenna pigment) is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis. List of photosynthetic pigments (in order of increasing polarity): Carotene: an orange pigment; Xanthophyll: a yellow pigment
By studying purple sulphur bacteria and green sulphur bacteria he was the first scientist to demonstrate, in 1931, that photosynthesis is a light-dependent redox reaction [2] in which hydrogen from an oxidizable compound reduces carbon dioxide to cellular materials. Expressed as: 2 H 2 A + CO 2 → 2A + CH 2 O + H 2 O
Cyanobacteria is the only prokaryotic group that performs oxygenic photosynthesis. Anoxygenic photosynthetic bacteria use PSI- and PSII-like photosystems, which are pigment protein complexes for capturing light. [5] Both of these photosystems use bacteriochlorophyll. There are multiple hypotheses for how oxygenic photosynthesis evolved.