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Location of the psa genes in the chloroplast genome of Arabidopsis thaliana.The 21 protein-coding genes involved in photosynthesis are displayed as green boxes. Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria.
Chloroplasts, containing thylakoids, visible in the cells of Ptychostomum capillare, a type of moss. A chloroplast (/ ˈ k l ɔːr ə ˌ p l æ s t,-p l ɑː s t /) [1] [2] is a type of organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells.
Oxygenic photosynthesis can be performed by plants and cyanobacteria; cyanobacteria are believed to be the progenitors of the photosystem-containing chloroplasts of eukaryotes. Photosynthetic bacteria that cannot produce oxygen have only one photosystem, which is similar to either PSI or PSII .
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 .
The electron transport chain of photosynthesis is often put in a diagram called the Z-scheme, because the redox diagram from P680 to P700 resembles the letter Z. [3] The final product of PSII is plastoquinol, a mobile electron carrier in the membrane. Plastoquinol transfers the electron from PSII to the proton pump, cytochrome b6f. The ultimate ...
Chloroplasts also need to balance the ratios of photosystem I and II for the electron transfer chain. The redox state of the electron carrier plastoquinone in the thylakoid membrane directly affects the transcription of chloroplast genes encoding proteins of the reaction centers of the photosystems, thus counteracting imbalances in the electron ...
Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. [9] The structure of Photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor. The core of Photosystem II consists of two subunits referred to as D1 and D2 ...
These organisms perform photosynthesis through organelles called chloroplasts and are believed to have originated about 2 billion years ago. [1] Comparing the genes of chloroplast and cyanobacteria strongly suggests that chloroplasts evolved as a result of endosymbiosis with cyanobacteria that gradually lost the genes required to be free-living.