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Chloroplasts can only be found in plants and algae, and they capture the sun's energy to make carbohydrates through photosynthesis. Diagram of the endomembrane system Endoplasmic reticulum : The endoplasmic reticulum (ER) is a transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules ...
Mitochondrion – A membrane-enclosed organelle found in most eukaryotic cells. [7] Often called "cellular power plants", mitochondria generate most of cells' supply of adenosine triphosphate (ATP), the body's main source of energy. Chloroplast – An organelles found in plant cells and eukaryotic algae that conduct photosynthesis.
The several plastids including chloroplasts are distributed among some but not all eukaryotes. There are also occasional exceptions to the number of membranes surrounding organelles, listed in the tables below (e.g., some that are listed as double-membrane are sometimes found with single or triple membranes).
In some plants such as cacti, chloroplasts are found in the stems, [186] though in most plants, chloroplasts are concentrated in the leaves. One square millimeter of leaf tissue can contain half a million chloroplasts. [11] Within a leaf, chloroplasts are mainly found in the mesophyll layers of a leaf, and the guard cells of stomata.
Chloroplasts probably became symbionts through a similar set of events, and are most likely descendants of cyanobacteria. [34] While not all eukaryotes have mitochondria or chloroplasts, mitochondria are found in most eukaryotes, and chloroplasts are found in all plants and algae.
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.
Each of the envelope membranes is a lipid bilayer that is between 6 and 8 nm thick. The lipid composition of the outer membrane has been found to be 48% phospholipids, 46% galactolipids and 7% sulfolipids, while the inner membrane has been found to contain 16% phospholipids, 79% galactolipids and 5% sulfolipids in spinach chloroplasts.
Organelles (literally "little organs") are usually membrane-bound structures inside the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, and in plant cells, chloroplasts.