Essay on Endosymbiosis

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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
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The protein-synthesizing machinery in mitochondria and chloroplasts resemble prokaryotes. This is shown through their ribosomal RNA and the structure of the ribosomes. The ribosomes are similar in size and structure to bacterial ribosomes. fMat is always the first amino acid that is in the mitochondria and chloroplasts transcripts. The antibiotics that act by blocking protein synthesis in bacteria also block protein synthesis in mitochondria and chloroplasts. These antibiotics do not interfere with protein synthesis in the cytoplasm of the eukaryotes. The inhibitors that effect the protein synthesis of eukaryotic ribosomes do not change the protein synthesis of the bacteria, mitochondria, or chloroplasts.

Mitochondria and chloroplasts have two membranes that surround them. The inner membrane is probably from the engulfed bacterium and this is supported by that the enzymes and proteins are most like their counterparts in prokaryotes. The outer membrane is formed from the plasma membrane or endoplasmic reticulum of the host cell. The electron transport enzymes and the H+ ATPase are only found in the mitochondria and chloroplasts of the eukaryotic cell. (2)

Currently, there are two major competing theories for the endosymbiotic origin of eukaryotic cells. The first theory claims that the eukaryotic cell is a combination of an archaeon with a
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