Chloroplast
The green powerhouses of plant and algal cells, evolved from ancient cyanobacteria.
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Photosynthetic eukaryotic cells contain organelles called chloroplasts that originated from cyanobacteria via organellogenesis.[1] These organelles are in constant motion within cells, and their movement patterns are affected by external conditions such as the color and intensity of light.[2] Plant cells cannot synthesize chloroplasts de novo; instead, each daughter cell inherits them during division.[2]
Quick Facts
- Etymology
- Greek chloros (green) and plastes (the one who forms)
- Origin
- Endosymbiotic from cyanobacteria, approximately two billion years ago
- Key feature
- Contains its own DNA separate from the cell nucleus
Facts from the source article.
Key facts and history
The first definitive description of a chloroplast was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell.[3] The origin of chloroplasts from cyanobacteria was first suggested by Russian biologist Konstantin Mereschkowski in 1905.[4] Approximately two billion years ago, a free-living cyanobacterium entered an early eukaryotic cell and persisted inside, an event called endosymbiosis.[5] Chloroplasts in vascular plants range from football to lens shaped, with a characteristic diameter of about 4-6 microns.[6]
There are usually about 40-60 stacks of disks termed grana per chloroplast.[6] In a typical photosynthetic leaf cell from plants like Arabidopsis, there are about 100 chloroplasts per cell.[6] Andreas Franz Wilhelm Schimper, in 1883, coined the term "chloroplastids" for these structures and noted their strong resemblance to cyanobacteria.[3][4] The serial endosymbiosis hypothesis proposes that chloroplasts evolved after mitochondria because mitochondria are present in all eukaryotes, whereas chloroplasts are not.[7]
What the research sources say
The "Cell Biology by the Numbers" account states that chloroplasts play a key role in the energy economy of the cells that harbor them.[6] From genomes that probably originally contained over 3000 genes, only about 130 genes remain in the chloroplasts of contemporary plants.[6] The "Basic Biology" account states that cyanobacteria became an organelle called a chloroplast, and over time green algae evolved into land plants.[8] Chloroplasts and mitochondria are thought to have originally been bacteria absorbed by eukaryotic cells and used as organelles for photosynthesis and respiration.[8]
Evidence indicates that chloroplasts arose through endosymbiosis, beginning when free-living photosynthetic cyanobacteria were engulfed approximately one billion years ago.[6]
References
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: "An Expanded Ribosomal Phylogeny of Cyanobacteria Supports a Deep Placement of Plastids", Frontiers in Microbiology, 2019 (original not read by us) en.wikipedia.org
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: Basic Biology, "Bacteria", 18 March 2016 (we also read that source) en.wikipedia.org
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: von Mohl, H. (1835/1837). Ueber die Vermehrung der Pflanzen-Zellen durch Teilung. Dissert. Tubingen 1835. Flora 1837, .; Schimper, "Über die Entwicklung der Chlorophyllkörner und Farbkörper", Bot. Zeitung, 1883, p. 105–14, 121–31, 137–46, 153–62; "Das botanische Praktikum", Gustav Fischer, 1884; "The structure and function of plastids", Springer, 2006, p. xxiii–xxxi; "Chloroplasts", Plenum, 1984 (original not read by us) en.wikipedia.org
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: "Biology", Benjamin Cummings (Pearson), 2009, p. 186–187; "The Chloroplast", 2009, p. 1–39; "The structure of cyanobacterial phycobilisomes: A model", Archives of Microbiology, 1979, p. 311–34; Mereschkowsky K, "Über Natur und Ursprung der Chromatophoren im Pflanzenreiche", Biol Centralbl, 1905, p. 593–604; Schimper, "Über die Entwicklung der Chlorophyllkörner und Farbkörper", Bot. Zeitung, 1883, p. 105–14, 121–31, 137–46, 153–62; Alberts, "Molecular biology of the cell", Garland, 2002; "Paulinella, a model for understanding plastid primary en.wikipedia.org
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: "Cell Biology by the Numbers: How large are chloroplasts?", book.bionumbers.org; "Early photosynthetic eukaryotes inhabited low-salinity habitats", Proceedings of the National Academy of Sciences of the United States of America, September 2017, p. E7737–E7745; Falcón, "Dating the cyanobacterial ancestor of the chloroplast", The ISME Journal, 4 March 2010, p. 777–783; "Biology", Benjamin Cummings (Pearson), 2009, p. 516; "The Chloroplast", 2009, p. 1–39 (we also read that source) en.wikipedia.org
- "Cell Biology by the Numbers: How large are chloroplasts?", book.bionumbers.org. facts only, no text reused. book.bionumbers.org
- Wikipedia, "Chloroplast" (CC BY-SA 4.0), which cites: "Biology", Benjamin Cummings (Pearson), 2009, p. 516; "The puzzle of plastid evolution", Current Biology, January 2009, p. R81-8; "Biology", Benjamin Cummings (Pearson), 2009, p. 516 (original not read by us) en.wikipedia.org
- Basic Biology, "Bacteria", 18 March 2016. facts only, no text reused. basicbiology.net
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Chloroplast (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Chloroplast (CC BY-SA 4.0).
- Word definitions: the , each quoted from its Wikipedia article.
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