Endosymbiosis Essay -- Biology Biological Papers

Endosymbiosis Endosymbiosis is the theory that eukaryotic cells were formed when a prokaryotic cell ingested some aerobic bacteria. The first step of the evolution of a eukaryotic cell is the infolding of the cellular membrane. This process takes place when the plasma membrane folds inwards and develops an envelope around a smaller prokaryotic cell. Once the smaller cell is engulfed, it becomes dependent upon its host cell. It relies on the host cell for organic molecules and inorganic compounds. However, the host cell also benefits because it has an increased output of ATP for cellular activities and becomes more productive. This ATP comes from the mitochondrion (the aerobe) that is engulfed. All eukaryotic cells contain the mitochondrion that is made through this process. However, only some of the eukaryotic cells (plant cells) form chloroplasts through endosymbiosis after the mitochondrion is formed. Some of the prokaryotic cells ingest cyanobacteria. These bacteria contain photosynthetic pigments that are useful in photosynthesis. The cyanobacteria become dependent upon the host cell and can no longer survive on its own. Over time, it becomes the chloroplast, a main organelle of plant cells. The chloroplast is then able to convert energy from the sun to energy-rich sugar molecules which are then converted to chemical energy in the form of ATP. (1) The evidence for endosymbiosis is most prevalent in the mitochondria and chloroplasts of cells. The ribosomes of mitochondria and chloroplasts resemble that of prokaryotic ribosomes because of their similar size, 70s. Mitochondria, chloroplasts, and prokaryotes all divide by binary fission. The genome of mitochondria and chloroplasts most resemble prokaryot... ...he nucleus as well. In conclusion, the nucleus is an endosymbiont of bacteria and archaea. The host cell most likely did not come from the bacteria. The host cell, chronocyte, was not a prokaryotic cell but one that had a cytoskeleton composed of actin and tubulin and a complex membrane system. The chronocyte contributed to the end product that is the euaryotic cell. Its contributions were the cytoskeleton, endoplasmic reticulum, Golgi apparatus, and major intracellular control systems. (3) References 1) Prescott, Lansing. Microbiology: 6th Edition. McGraw Hill: Boston. 2002. 2) Microbe Ecology: Lecture 18. http://jan.ucc.nau.edu/~bah/BIO471/Lecture18/Lecture18.html. Accessed via Internet: 26 November 2004. 3) Hartman, Hyman, and Fedorov, Alexei. The Origin of the eukaryotic cell: A genomic investigation. 5 February 2002.