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Eukaryotic cells contain organelles including mitochondria, which provide energy for cell functions; chloroplasts, which create sugars by photosynthesis, in plants; and ribosomes, which synthesise proteins. Cells were discovered by Robert Hooke in 1665, who named them after their resemblance to cells inhabited by Christian monks in a monastery.
Both organelles, the mitochondria and chloroplasts (in photosynthetic organisms), are compartments that are believed to be of endosymbiotic origin. Other compartments such as peroxisomes , lysosomes , the endoplasmic reticulum , the cell nucleus or the Golgi apparatus are not of endosymbiotic origin.
A mitochondrion (pl. mitochondria) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi.Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. [2]
The plant cells which contain chloroplasts are usually parenchyma cells, though chloroplasts can also be found in collenchyma tissue. [185] A plant cell which contains chloroplasts is known as a chlorenchyma cell. A typical chlorenchyma cell of a land plant contains about 10 to 100 chloroplasts.
Comparatively, in the laboratory, most cultured cells—which are large compared to normal plant cells—produce very long and abundant stromules that extend to the cell periphery. In 2014, evidence was found of the possible loss of plastid genome in Rafflesia lagascae , a non-photosynthetic parasitic flowering plant, and in Polytomella , a ...
Like mitochondria, chloroplasts have a double-membrane envelope, called the chloroplast envelope, but unlike mitochondria, chloroplasts also have internal membrane structures called thylakoids. Furthermore, one or two additional membranes may enclose chloroplasts in organisms that underwent secondary endosymbiosis , such as the euglenids and ...
Mitochondria and plastids contain their own ribosomes; these are more similar to those of bacteria (70S) than those of eukaryotes. [77] Proteins created by mitochondria and chloroplasts use N-formylmethionine as the initiating amino acid, as do proteins created by bacteria but not proteins created by eukaryotic nuclear genes or archaea. [78] [79]
The ATP synthase of mitochondria and chloroplasts is an anabolic enzyme that harnesses the energy of a transmembrane proton gradient as an energy source for adding an inorganic phosphate group to a molecule of adenosine diphosphate (ADP) to form a molecule of adenosine triphosphate (ATP).