Notes

Chloroplast;
Definition:
(From Google)
chlo·ro·plast
ˈklôrəˌplast/Submit
nounBOTANY
noun: chloroplast; plural noun: chloroplasts
(in green plant cells) a plastid that contains chlorophyll and in which photosynthesis takes place.
Origin

late 19th century: coined in German from Greek khlōros ‘green’ + plastos ‘formed.’
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Use over time for: chloroplast
Chloroplasts /ˈklɔːrəˌplæsts, -plɑːsts/[1][2] are organelles, specialized subunits, in plant and algal cells. Their discovery inside plant cells is usually credited to Julius von Sachs (1832–1897), an influential botanist and author of standard botanical textbooks – sometimes called "The Father of Plant Physiology".

Chloroplasts' main role is to conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight and converts it and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water. They then use the ATP and NADPH to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, much amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat.[3]

A chloroplast is a type of organelle known as a plastid, characterized by its high concentration of chlorophyll. Other plastid types, such as the leucoplast and the chromoplast, contain little chlorophyll and do not carry out photosynthesis.

Chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally pinch in two to reproduce. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts, like mitochondria, contain their own DNA, which is thought to be inherited from their ancestor—a photosynthetic cyanobacterium that was engulfed by an early eukaryotic cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division.



With one exception (the amoeboid Paulinella chromatophora), all chloroplasts can probably be traced back to a single endosymbiotic event, when a cyanobacterium was engulfed by the eukaryote. Despite this, chloroplasts can be found in an extremely wide set of organisms, some not even directly related to each other—a consequence of many secondary and even tertiary endosymbiotic events.

The word chloroplast is derived from the Greek words chloros (χλωρός), which means green, and plastes (πλάστης), which means "the one who forms".[4]

Discovery[edit]
The first definitive description of a chloroplast (Chlorophyllkörnen, "grain of chlorophyll") was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell.[5] In 1883, A. F. W. Schimper would name these bodies as "chloroplastids" (Chloroplastiden).[6] In 1884, Eduard Strasburger adopted the term "chloroplasts" (Chloroplasten).[7][8][9]

Chloroplast lineages and evolution[edit]
Chloroplasts are one of many types of organelles in the plant cell. They are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell. Mitochondria are thought to have come from a similar event, where an aerobic prokaryote was engulfed.[10] This origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905[11] after Andreas Schimper observed in 1883 that chloroplasts closely resemble cyanobacteria.[6] Chloroplasts are only found in plants, algae,[12] and the amoeboid Paulinella chromatophora.

Cyanobacterial ancestor[edit]
Main article: Cyanobacteria
Cyanobacteria are considered the ancestors of chloroplasts. They are sometimes called blue-green algae even though they are prokaryotes. They are a diverse phylum of bacteria capable of carrying out photosynthesis, and are gram-negative, meaning that they have two cell membranes. Cyanobacteria also contain a peptidoglycan cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes.[13] Like chloroplasts, they have thylakoids within.[14] On the thylakoid membranes are photosynthetic pigments, including chlorophyll a.[15] Phycobilins are also common cyanobacterial pigments, usually organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though).[15][16]

SO in term of my own words it a very important storage organ in which the energy is stored, and preserved in most cases but used as well, It is a bacteria in only plant cells unforunately, humans well missed out on this, we use food instead, physical food, not sunshine and water, we aren't plants, but mammals, imagine eating the air basically, weird wouldn't you say? Maybe in the future we could evolve into perfect plant like beings but until then, just stay healthy and think about one of the amazing parts of a basic plant, science is amazing!