Chloroplast - Knowledge

3254:. It has been established that some plants have linear cpDNA, such as maize, and that more species still contain complex structures that scientists do not yet understand. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not expand the multiple A --> G gradients seen in plastomes. Because of the failure to explain the deamination gradient as well as the numerous plant species that have been shown to have circular cpDNA, the predominant theory continues to hold that most cpDNA is circular and most likely replicates via a D loop mechanism. 481: 3557: 7592: 3849: 3848: 4452: 5803: 7579: 1439: 6131: 6033: 5250: 55: 3733: 7492: 1015: 1118: 830: 3832: 1461: 35: 6480: 823: 3243:

replication forks were most likely present and the direction that they initially opened (the highest gradient is most likely nearest the start site because it was single stranded for the longest amount of time). This mechanism is still the leading theory today; however, a second theory suggests that most cpDNA is actually linear and replicates through homologous recombination. It further contends that only a minority of the genetic material is kept in circular chromosomes while the rest is in branched, linear, or other complex structures.

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columns which bifurcates into multiple parallel discs forming the granum-stroma assembly. The helical model was supported by several additional works, but ultimately it was determined in 2019 that features from both the helical and bifurcation models are consolidated by newly discovered left-handed helical membrane junctions. Likely for ease, the thylakoid system is still commonly depicted by older "hub and spoke" models where the grana are connected to each other by tubes of stromal thylakoids.

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helices (~20°), but ¼ the pitch. Approximately 4 left-handed helical junctions are present per granum, resulting in a pitch-balanced array of right- and left-handed helical membrane surfaces of different radii and pitch that consolidate the network with minimal surface and bending energies. While different parts of the thylakoid system contain different membrane proteins, the thylakoid membranes are continuous and the thylakoid space they enclose form a single continuous labyrinth.

4814: 1008: 2534: 7413: 7120: 6226: 3412: 1853: 1599: 1022: 17828: 4891: 993: 3203: 3858: 4209: 2193: 2124: 2277: 1001: 852: 3837: 1550: 480: 7546:, or PD rings form. The inner plastid-dividing ring is located in the inner side of the chloroplast's inner membrane, and is formed first. The outer plastid-dividing ring is found wrapped around the outer chloroplast membrane. It consists of filaments about 5 nanometers across, arranged in rows 6.4 nanometers apart, and shrinks to squeeze the chloroplast. This is when chloroplast constriction begins. 3859: 3556: 844: 3857: 2498:(cpDNA) was identified biochemically in 1959, and confirmed by electron microscopy in 1962. The discoveries that the chloroplast contains ribosomes and performs protein synthesis revealed that the chloroplast is genetically semi-autonomous. Chloroplast DNA was first sequenced in 1986. Since then, hundreds of chloroplast DNAs from various species have been 3108:), suggesting that they predate the chloroplast, though some chloroplast DNAs have since lost or flipped the inverted repeats (making them direct repeats). It is possible that the inverted repeats help stabilize the rest of the chloroplast genome, as chloroplast DNAs which have lost some of the inverted repeat segments tend to get rearranged more. 1930:

supporting it, typically forming a flexible pellicle (thin skin). In dinoflagellates they often form armor plates. Many members contain a red-algal derived plastid. One notable characteristic of this diverse group is the frequent loss of photosynthesis. However, a majority of these heterotrophs continue to process a non-photosynthetic plastid.

3844: 7659:, but are slow to complete division—they require exposure to bright white light to complete division. Spinach leaves grown under green light have been observed to contain many large dumbbell-shaped chloroplasts. Exposure to white light can stimulate these chloroplasts to divide and reduce the population of dumbbell-shaped chloroplasts. 6159:. This ability to distribute chloroplasts so that they can take shelter behind each other or spread out may be the reason why land plants evolved to have many small chloroplasts instead of a few big ones. Chloroplast movement is considered one of the most closely regulated stimulus-response systems that can be found in plants. 4783:. They are not found in higher plants. Pyrenoids are roughly spherical and highly refractive bodies which are a site of starch accumulation in plants that contain them. They consist of a matrix opaque to electrons, surrounded by two hemispherical starch plates. The starch is accumulated as the pyrenoids mature. In algae with 3219:

replication with a rolling circle mechanism. Transcription starts at specific points of origin. Multiple replication forks open up, allowing replication machinery to transcribe the DNA. As replication continues, the forks grow and eventually converge. The new cpDNA structures separate, creating daughter cpDNA chromosomes.

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simply reenergizes depleted electrons at the end of an electron transport chain. Normally, the reenergized electrons are taken by NADP, though sometimes they can flow back down more H-pumping electron transport chains to transport more hydrogen ions into the thylakoid space to generate more ATP. This

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The stroma lamellae extend as large sheets perpendicular to the grana columns. These sheets are connected to the right-handed helices either directly or through bifurcations that form left-handed helical membrane surfaces. The left-handed helical surfaces have a similar tilt angle to the right-handed

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Grana consist of a stacks of flattened circular granal thylakoids that resemble pancakes. Each granum can contain anywhere from two to a hundred thylakoids, though grana with 10–20 thylakoids are most common. Wrapped around the grana are multiple parallel right-handed helical stromal thylakoids, also

6924:, and produces no sugar. It can waste up to half the carbon fixed by the Calvin cycle. Several mechanisms have evolved in different lineages that raise the carbon dioxide concentration relative to oxygen within the chloroplast, increasing the efficiency of photosynthesis. These mechanisms are called 4929:

model, in which granum stacks of thylakoids are wrapped by helical stromal thylakoids. Another model known as the 'bifurcation model', which was based on the first electron tomography study of plant thylakoid membranes, depicts the stromal membranes as wide lamellar sheets perpendicular to the grana

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compared to that of free-living cyanobacteria. Chloroplasts may contain 60–100 genes whereas cyanobacteria often have more than 1500 genes in their genome. Recently, a plastid without a genome was found, demonstrating chloroplasts can lose their genome during endosymbiotic the gene transfer process.

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proteins assemble around the outer plastid-dividing ring, helping provide force to squeeze the chloroplast. Meanwhile, the Z-ring and the inner plastid-dividing ring break down. During this stage, the many chloroplast DNA plasmids floating around in the stroma are partitioned and distributed to the

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supply, which indirectly stimulates chloroplast starch synthesis. While linked to low photosynthesis rates, the starch grains themselves may not necessarily interfere significantly with the efficiency of photosynthesis, and might simply be a side effect of another photosynthesis-depressing factor.

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The chloroplasts of plant and algal cells can orient themselves to best suit the available light. In low-light conditions, they will spread out in a sheet—maximizing the surface area to absorb light. Under intense light, they will seek shelter by aligning in vertical columns along the plant cell's

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are large protein complexes which jut out into the stroma. They can't fit in the appressed granal membranes, and so are found in the stromal thylakoid membrane—the edges of the granal thylakoid disks and the stromal thylakoids. These large protein complexes may act as spacers between the sheets of

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or to another plastoglobulus attached to a thylakoid, a configuration that allows a plastoglobulus to exchange its contents with the thylakoid network. In normal green chloroplasts, the vast majority of plastoglobuli occur singularly, attached directly to their parent thylakoid. In old or stressed

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The alveolates are a major clade of unicellular eukaryotes of both autotrophic and heterotrophic members. The most notable shared characteristic is the presence of cortical (outer-region) alveoli (sacs). These are flattened vesicles (sacs) packed into a continuous layer just under the membrane and

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In cpDNA, there are several A → G deamination gradients. DNA becomes susceptible to deamination events when it is single stranded. When replication forks form, the strand not being copied is single stranded, and thus at risk for A → G deamination. Therefore, gradients in deamination indicate that

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The biosynthesis of fatty acids from acetyl-CoA primarily requires two enzymes. Acetyl-CoA carboxylase creates malonyl-CoA, used in both the first step and the extension steps of synthesis. Fatty acid synthase (FAS) is a large complex of enzymes and cofactors including acyl carrier protein (ACP)

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of the host. From genomes that probably originally contained over 3000 genes only about 130 genes remain in the chloroplasts of contemporary plants. Some of its proteins were then synthesized in the cytoplasm of the host cell, and imported back into the chloroplast (formerly the cyanobacterium).

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since the 1970s. The results of the microscopy experiments led to the idea that chloroplast DNA replicates using a double displacement loop (D-loop). As the D-loop moves through the circular DNA, it adopts a theta intermediary form, also known as a Cairns replication intermediate, and completes

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and other pigments, many are reddish to purple from the combination. The red phycoerytherin pigment is an adaptation to help red algae catch more sunlight in deep water—as such, some red algae that live in shallow water have less phycoerythrin in their rhodoplasts, and can appear more greenish.

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Nishiyama, Tomoaki; Sakayama, Hidetoshi; de Vries, Jan; Buschmann, Henrik; Saint-Marcoux, Denis; Ullrich, Kristian K.; Haas, Fabian B.; Vanderstraeten, Lisa; Becker, Dirk; Lang, Daniel; Vosolsobě, Stanislav; Rombauts, Stephane; Wilhelmsson, Per K.I.; Janitza, Philipp; Kern, Ramona (July 2018).

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that contain a single chloroplast, regulation of chloroplast division is extremely important to ensure that each daughter cell receives a chloroplast—chloroplasts can't be made from scratch. In organisms like plants, whose cells contain multiple chloroplasts, coordination is looser and less

6130: 2169:. Peridinin is not found in any other group of chloroplasts. The peridinin chloroplast is bounded by three membranes (occasionally two), having lost the red algal endosymbiont's original cell membrane. The outermost membrane is not connected to the endoplasmic reticulum. They contain a 3838: 11909:

Dadras, Armin; Fürst-Jansen, Janine M. R.; Darienko, Tatyana; Krone, Denis; Scholz, Patricia; Sun, Siqi; Herrfurth, Cornelia; Rieseberg, Tim P.; Irisarri, Iker; Steinkamp, Rasmus; Hansen, Maike; Buschmann, Henrik; Valerius, Oliver; Braus, Gerhard H.; Hoecker, Ute (28 August 2023).

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membrane from the host, which was probably lost. The new cellular resident quickly became an advantage, providing food for the eukaryotic host, which allowed it to live within it. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to the

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being the possible earliest diverging lineage. The glaucophyte chloroplast group is the smallest of the three primary chloroplast lineages, being found in only 13 species, and is thought to be the one that branched off the earliest. Glaucophytes have chloroplasts that retain a

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The prevailing model of the granum-stroma assembly is stacks of granal thylakoids wrapped by right-handed helical stromal thylakoids which are connected to large parallel sheets of stromal thylakoids and adjacent right-handed helices by left-handed helical structures. (Based

6190:, chloroplast movement is influenced by red light in addition to blue light, though very long red wavelengths inhibit movement rather than speeding it up. Blue light generally causes chloroplasts to seek shelter, while red light draws them out to maximize light absorption. 4105:

ion flow is in the opposite direction compared to oxidative phosphorylation in mitochondria. In addition, in terms of function, the inner chloroplast membrane, which regulates metabolite passage and synthesizes some materials, has no counterpart in the mitochondrion.

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Chlorarachniophyte chloroplasts are bounded by four membranes, except near the cell membrane, where the chloroplast membranes fuse into a double membrane. Their thylakoids are arranged in loose stacks of three. Chlorarachniophytes have a form of polysaccharide called

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Of the five or six rings involved in chloroplast division, only the outer plastid-dividing ring is present for the entire constriction and division phase—while the Z-ring forms first, constriction does not begin until the outer plastid-dividing ring forms.

3370:. Recent research indicates that parts of the retrograde signaling network once considered characteristic for land plants emerged already in an algal progenitor, integrating into co-expressed cohorts of genes in the closest algal relatives of land plants. 6352:

which can serve as defense-signals. As cellular signals, reactive oxygen species are unstable molecules, so they probably don't leave the chloroplast, but instead pass on their signal to an unknown second messenger molecule. All these molecules initiate

4821:(Top) 10-nm-thick STEM tomographic slice of a lettuce chloroplast. Grana stacks are interconnected by unstacked stromal thylakoids, called "stroma lamellae". Round inclusions associated with the thylakoids are plastoglobules. Scalebar=200 nm. See. 7047:, probably because it has trouble crossing membranes to get to where it is needed. The chloroplast is known to make the precursors to methionine but it is unclear whether the organelle carries out the last leg of the pathway or if it happens in the 3237:

Over time, base changes in the DNA sequence can arise from deamination mutations. When adenine is deaminated, it becomes hypoxanthine, which can pair with cytosine. During replication, the cytosine will pair with guanine, causing an A --> G base

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Of the approximately 3000 proteins found in chloroplasts, some 95% of them are encoded by nuclear genes. Many of the chloroplast's protein complexes consist of subunits from both the chloroplast genome and the host's nuclear genome. As a result,

1945:, they're parasitic, and have a nonphotosynthetic chloroplast. They were once thought to be related to the helicosproidia, but it is now known that the helicosproida are green algae rather than part of the CASH lineage. The apicomplexans include 11841:

Zhao, Chenchen; Wang, Yuanyuan; Chan, Kai Xun; Marchant, D. Blaine; Franks, Peter J.; Randall, David; Tee, Estee E.; Chen, Guang; Ramesh, Sunita; Phua, Su Yin; Zhang, Ben; Hills, Adrian; Dai, Fei; Xue, Dawei; Gilliham, Matthew (12 March 2019).

6524:(ADP), which stores energy in a cell and powers most cellular activities. ATP is the energized form, while ADP is the (partially) depleted form. NADP is an electron carrier which ferries high energy electrons. In the light reactions, it gets 3854: 1165:

is an exception that acquired a photosynthetic cyanobacterial endosymbiont more recently. It is not clear whether that symbiont is closely related to the ancestral chloroplast of other eukaryotes. Being in the early stages of endosymbiosis,

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Whether or not primary chloroplasts came from a single endosymbiotic event, or many independent engulfments across various eukaryotic lineages, has long been debated. It is now generally held that organisms with primary chloroplasts share

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membranes, (depending on whether the entire diatom endosymbiont is counted as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original

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are a rare group of organisms that also contain chloroplasts derived from green algae, though their story is more complicated than that of the euglenophytes. The ancestor of chlorarachniophytes is thought to have been a eukaryote with a

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stocked. Within a few minutes of light exposure, the prolamellar body begins to reorganize into stacks of thylakoids, and chlorophyll starts to be produced. This process, where the etioplast becomes a chloroplast, takes several hours.

3082:, which separate a long single copy section (LSC) from a short single copy section (SSC). While a given pair of inverted repeats are rarely completely identical, they are always very similar to each other, apparently resulting from 1192:

genome, but much larger than the approximately 150,000 base pair genome of the more assimilated chloroplast. Chromatophores have transferred much less of their DNA to the nucleus of their host. About 0.3–0.8% of the nuclear DNA in

3841: 2347:. However the diatom endosymbiont can't store its own food—its storage polysaccharide is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a 4254:, meaning "wall"). Other chloroplasts were assumed to have lost the cyanobacterial wall, leaving an intermembrane space between the two chloroplast envelope membranes, but has since been found also in moss, lycophytes and ferns. 5249: 3845: 1407:

Many other organisms obtained chloroplasts from the primary chloroplast lineages through secondary endosymbiosis—engulfing a red or green alga that contained a chloroplast. These chloroplasts are known as secondary plastids.

7750:. While the reliability of this mechanism has not yet been studied for all relevant crop species, recent results in tobacco plants are promising, showing a failed containment rate of transplastomic plants at 3 in 1,000,000. 5953:

and returns to the mesophyll. Bundle sheath chloroplasts do not carry out the light reactions, preventing oxygen from building up in them and disrupting RuBisCO activity. Because of this, they lack thylakoids organized into

7268:, though the two terms are sometimes used interchangeably. There are many other types of plastids, which carry out various functions. All chloroplasts in a plant are descended from undifferentiated proplastids found in the 4061:

There are some common misconceptions about the outer and inner chloroplast membranes. The fact that chloroplasts are surrounded by a double membrane is often cited as evidence that they are the descendants of endosymbiotic

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chloroplasts have three membranes—it is thought that the membrane of the primary endosymbiont was lost, leaving the cyanobacterial membranes, and the secondary host's phagosomal membrane. Euglenophyte chloroplasts have a

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with similar structure to the apicomplexans, provides an important link in the evolutionary history of the apicomplexans and dinophytes. Their plastids have four membranes, lack chlorophyll c and use the type II form of

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are also found in the photosystems. There are about thirty photosynthetic carotenoids. They help transfer and dissipate excess energy, and their bright colors sometimes override the chlorophyll green, like during the

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tracks, and the fact that the microfilament mesh changes shape to form a honeycomb structure surrounding the chloroplasts after they have moved suggests that microfilaments may help to anchor chloroplasts in place.

3840: 2258:. However, the haptophyte was heavily reduced, stripped of a few membranes and its nucleus, leaving only its chloroplast (with its original double membrane), and possibly one or two additional membranes around it. 5036:

with more thylakoid membrane area than chloroplasts exposed to bright light, which have smaller and fewer grana and less thylakoid area. Thylakoid extent can change within minutes of light exposure or removal.

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is a genus of nonphotosynthetic parasitic green algae that is thought to contain a vestigial chloroplast. Genes from a chloroplast and nuclear genes indicating the presence of a chloroplast have been found in

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that do not contain any plastids. There are many other documented mechanisms that prevent paternal inheritance in these flowering plants, such as different rates of chloroplast replication within the embryo.

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Hansen AK, Escobar LK, Gilbert LE, Jansen RK (January 2007). "Paternal, maternal, and biparental inheritance of the chloroplast genome in Passiflora (Passifloraceae): implications for phylogenetic studies".

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Shaw J, Lickey EB, Schilling EE, Small RL (March 2007). "Comparison of whole chloroplast genome sequences to choose noncoding regions for phylogenetic studies in angiosperms: the tortoise and the hare III".

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engulfed a chloroplast-containing alga but failed to digest it—much like the cyanobacterium at the beginning of this story. The engulfed alga was broken down, leaving only its chloroplast, and sometimes its

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probably took up different heterokontophytes. Because the haptophyte chloroplast has four membranes, tertiary endosymbiosis would be expected to create a six membraned chloroplast, adding the haptophyte's

7671:, chloroplasts are usually inherited from a single parent. Biparental chloroplast inheritance—where plastid genes are inherited from both parent plants—occurs in very low levels in some flowering plants. 3853: 3851: 1117: 3323:

in many CASH lineages. Even if a chloroplast is eventually lost, the genes it donated to the former host's nucleus persist, providing evidence for the lost chloroplast's existence. For example, while

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which holds the acyl chain as it is synthesized. The initiation of synthesis begins with the condensation of malonyl-ACP with acetyl-CoA to produce ketobutyryl-ACP. 2 reductions involving the use of

6807:, or G3P sugar molecules. Most of the G3P molecules are recycled back into RuBP using energy from more ATP, but one out of every six produced leaves the cycle—the end product of the dark reactions. 2362:

The diatom endosymbiont is bounded by a single membrane, inside it are chloroplasts with four membranes. Like the diatom endosymbiont's diatom ancestor, the chloroplasts have triplet thylakoids and

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can also be converted to chromoplasts, and it is possible for proplastids to develop straight into chromoplasts. Chromoplasts and amyloplasts can also become chloroplasts, like what happens when a

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The mechanism for chloroplast DNA (cpDNA) replication has not been conclusively determined, but two main models have been proposed. Scientists have attempted to observe chloroplast replication via

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synthesis—in fact, apicomplexans die when something interferes with this apicoplast function, and when apicomplexans are grown in an isopentenyl pyrophosphate-rich medium, they dump the organelle.

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of the thylakoid membrane, or bud from existing plastoglobuli—though they never detach and float off into the stroma. Practically all plastoglobuli form on or near the highly curved edges of the

6314:, where infected cells release signals warning the rest of the plant of a pathogen's presence. Chloroplasts stimulate both responses by purposely damaging their photosynthetic system, producing 278:, when a cyanobacterium was engulfed by a eukaryote. Despite this, chloroplasts can be found in an extremely wide set of organisms, some not directly related to each other—a consequence of many 13376:

Zeeman SC, Delatte T, Messerli G, Umhang M, Stettler M, Mettler T, Streb S, Reinhold H, Kötting O (2007). "Starch breakdown: Recent discoveries suggest distinct pathways and novel mechanisms".

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leaf tissues as the leaf matures, if exposed to the required light. This process involves invaginations of the inner plastid membrane, forming sheets of membrane that project into the internal

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may also be involved, but it is not very well understood. These proteins are active at the poles of the chloroplast, preventing Z-ring formation there, but near the center of the chloroplast,

4196:. When they were first observed in 1962, some plant biologists dismissed the structures as artifactual, claiming that stromules were just oddly shaped chloroplasts with constricted regions or 761:

in. The starch that they synthesize collects outside the chloroplast. Like cyanobacteria, glaucophyte and rhodophyte chloroplast thylakoids are studded with light collecting structures called

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Light, however, does not guarantee that a proplastid will develop into a chloroplast. Whether a proplastid develops into a chloroplast some other kind of plastid is mostly controlled by the

4823:(Bottom) Large-scale 3D model generated from segmentation of tomographic reconstructions by STEM. grana=yellow; stroma lamellae=green; plastoglobules=purple; chloroplast envelope=blue. See. 7568:

A remnant of the outer plastid dividing ring remains floating between the two daughter chloroplasts, and a remnant of the dynamin ring remains attached to one of the daughter chloroplasts.

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in the chloroplast are now synthesized in the cytoplasm of the plant cell. These proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.

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Apicoplasts have lost all photosynthetic function, and contain no photosynthetic pigments or true thylakoids. They are bounded by four membranes, but the membranes are not connected to the

3751:, chloroplasts are generally lens-shaped, 3–10 μm in diameter and 1–3 μm thick. Corn seedling chloroplasts are ≈20 μm in volume. Greater diversity in chloroplast shapes exists among the 15379:

Joyard J, Ferro M, Masselon C, Seigneurin-Berny D, Salvi D, Garin J, Rolland N (April 2010). "Chloroplast proteomics highlights the subcellular compartmentation of lipid metabolism".

7462:, chloroplast division is the only way new chloroplasts are formed. There is no proplastid differentiation—when an algal cell divides, its chloroplast divides along with it, and each 6972:

around 4, while the stroma is slightly basic, with a pH of around 8. The optimal stroma pH for the Calvin cycle is 8.1, with the reaction nearly stopping when the pH falls below 7.3.

3673:. At the same time, they have to keep just enough shape so that they can be recognized by the chloroplast. These proteins also help the polypeptide get imported into the chloroplast. 3116:

New chloroplasts may contain up to 100 copies of their DNA, though the number of chloroplast DNA copies decreases to about 15–20 as the chloroplasts age. They are usually packed into

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Later, the dynamins migrate under the outer plastid dividing ring, into direct contact with the chloroplast's outer membrane, to cleave the chloroplast in two daughter chloroplasts.

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long each and containing as few as four or as many as over 150 genes. Inverted repeats in plants tend to be at the upper end of this range, each being 20,000–25,000 base pairs long.

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algal derived chloroplast. It is then thought to have lost its first red algal chloroplast, and later engulfed a green alga, giving it its second, green algal derived chloroplast.

5974:—the only protein complex needed for cyclic electron flow. Because the job of bundle sheath chloroplasts is to carry out the Calvin cycle and make sugar, they often contain large 1748: 6730: 17658: 5923:

mesophyll cells and bundle sheath cells are specialized for each stage of photosynthesis. In mesophyll cells, chloroplasts are specialized for the light reactions, so they lack

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that's added to the N-terminus of the protein precursor. Sometimes the transit sequence is found on the C-terminus of the protein, or within the functional part of the protein.

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Werdan K, Heldt HW, Milovancev M (August 1975). "The role of pH in the regulation of carbon fixation in the chloroplast stroma. Studies on CO2 fixation in the light and dark".

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state, chloroplasts and other plastids can turn back into proplastids. Chloroplast, amyloplast, chromoplast, proplastid are not absolute; state—intermediate forms are common.

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The peridinin chloroplast is thought to be the dinophytes' "original" chloroplast, which has been lost, reduced, replaced, or has company in several other dinophyte lineages.

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and its close relatives are dinophytes (see below) that lost their original peridinin chloroplast and replaced it with a green algal derived chloroplast (more specifically, a

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concentrations, these starch grains may grow very large, distorting the grana and thylakoids. The starch granules displace the thylakoids, but leave them intact. Waterlogged

17864: 1771:, or cryptomonads are a group of algae that contain a red-algal derived chloroplast. Cryptophyte chloroplasts contain a nucleomorph that superficially resembles that of the 11658:

Koussevitzky S, Nott A, Mockler TC, Hong F, Sachetto-Martins G, Surpin M, et al. (May 2007). "Signals from chloroplasts converge to regulate nuclear gene expression".

10043:"The complete chloroplast genome of the chlorarachniophyte Bigelowiella natans: evidence for independent origins of chlorarachniophyte and euglenid secondary endosymbionts" 3669:

prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the

2373:, the diatom endosymbiont's chloroplasts aren't the only chloroplasts in the dinophyte. The original three-membraned peridinin chloroplast is still around, converted to an 7742:

a valuable tool for the creation and cultivation of genetically modified plants that are biologically contained, thus posing significantly lower environmental risks. This

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are similar and closely related to cryptophytes or heterokontophytes. Their chloroplasts lack a nucleomorph, their thylakoids are in stacks of three, and they synthesize

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than in offspring from parents of the same species. This suggests that incompatible hybrid genes might interfere with the mechanisms that prevent paternal inheritance.

7170:. Acetate in the cytosol is unavailable for lipid biosynthesis in the plastid. The typical length of fatty acids produced in the plastid are 16 or 18 carbons, with 0-3 4460:

Comparison of a chloroplast ribosome (green) and a bacterial ribosome (yellow). Important features common to both ribosomes and chloroplast-unique features are labeled.

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must be coordinated between the chloroplast and the nucleus. The chloroplast is mostly under nuclear control, though chloroplasts can also give out signals regulating

7473:—their DNA replication is not synchronized or limited to that of their host cells. Much of what we know about chloroplast division comes from studying organisms like 1096:

their chloroplasts, and in plants and some algae, the chloroplast thylakoids are arranged in grana stacks. Some green algal chloroplasts contain a structure called a

4641:, they can be big enough to distort the shape of the organelle. Starch granules are simply accumulations of starch in the stroma, and are not bounded by a membrane. 7614: 3352:, corresponding to about 4,500 protein-coding genes. There have been a few recent transfers of genes from the chloroplast DNA to the nuclear genome in land plants. 17663: 7696:

often inherit chloroplasts maternally. Flowering plants were once thought to only inherit chloroplasts maternally. However, there are now many documented cases of

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protein complex. This allows them to stack tightly, forming grana with many layers of tightly appressed membrane, called granal membrane, increasing stability and

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ancestor, secondary chloroplasts have additional membranes outside of the original two, as a result of the secondary endosymbiotic event, when a nonphotosynthetic

808: 790: 6203:, have shown that chloroplasts can get moving within five minutes of light exposure, though they don't initially show any net directionality. They may move along 2181:

and fragmented into many small circles. Most of the genome has migrated to the nucleus, and only critical photosynthesis-related genes remain in the chloroplast.

6156: 3720:. Chloroplast polypeptide chains probably often travel through the two complexes at the same time, but the TIC complex can also retrieve preproteins lost in the 784: 7245: 6479: 1980:. The fact that apicomplexans still keep their nonphotosynthetic chloroplast around demonstrates how the chloroplast carries out important functions other than 4466:

Chloroplasts have their own ribosomes, which they use to synthesize a small fraction of their proteins. Chloroplast ribosomes are about two-thirds the size of

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parent. For this reason, glaucophyte chloroplasts are also known as 'muroplasts' (besides 'cyanoplasts' or 'cyanelles'). Glaucophyte chloroplasts also contain

11503:"Evolutionary analysis of Arabidopsis, cyanobacterial, and chloroplast genomes reveals plastid phylogeny and thousands of cyanobacterial genes in the nucleus" 9937:

Chaal BK, Green BR (February 2005). "Protein import pathways in 'complex' chloroplasts derived from secondary endosymbiosis involving a red algal ancestor".

2120:), giving many a golden-brown color. All dinophytes store starch in their cytoplasm, and most have chloroplasts with thylakoids arranged in stacks of three. 1725: 1708:

Chlorarachniophyte chloroplasts are notable because the green alga they are derived from has not been completely broken down—its nucleus still persists as a

15446:

Bao X, Focke M, Pollard M, Ohlrogge J. 2000. Understanding in vivo carbon precursor supply for fatty acid synthesis in leaf tissue. Plant Journal 22, 39–50.

7451:. These proplastids differentiate into chloroplasts, which divide to create the 30–70 chloroplasts found in a mature photosynthetic plant cell. If the cell 6336:

Chloroplasts can serve as cellular sensors. After detecting stress in a cell, which might be due to a pathogen, chloroplasts begin producing molecules like

7682:, and chloroplasts from one parent being excluded from the embryo. Parental chloroplasts can be sorted so that only one type is present in each offspring. 5356:

is one of the pigments that makes many red algae red. Phycobilins often organize into relatively large protein complexes about 40 nanometers across called

3226:

seen in cpDNA. Deamination occurs when an amino group is lost and is a mutation that often results in base changes. When adenine is deaminated, it becomes

1803: 7874: 7606: 3055:

With few exceptions, most chloroplasts have their entire chloroplast genome combined into a single large circular DNA molecule, typically 120,000–170,000

12144:"A transit peptide-like sorting signal at the C terminus directs the Bienertia sinuspersici preprotein receptor Toc159 to the chloroplast outer membrane" 7182:

and one dehydration creates butyryl-ACP. Extension of the fatty acid comes from repeated cycles of malonyl-ACP condensation, reduction, and dehydration.

6908:

can occur when the oxygen concentration is too high. RuBisCO cannot distinguish between oxygen and carbon dioxide very well, so it can accidentally add O

6578:, with more hydrogen ions (up to a thousand times as many) inside the thylakoid system than in the stroma. The hydrogen ions in the thylakoid space then 6002:

Not all cells in a multicellular plant contain chloroplasts. All green parts of a plant contain chloroplasts—the chloroplasts, or more specifically, the

1784: 1713: 13277:"Plastoglobules are lipoprotein subcompartments of the chloroplast that are permanently coupled to thylakoid membranes and contain biosynthetic enzymes" 5372:

chloroplasts and some cyanobacteria don't have their phycobilin pigments organized into phycobilisomes, and keep them in their thylakoid space instead.

3100:

among land plants, and accumulate few mutations. Similar inverted repeats exist in the genomes of cyanobacteria and the other two chloroplast lineages (

2020:

is a newly discovered group of algae from Australian corals which comprises some close photosynthetic relatives of the apicomplexans. The first member,

17796: 2070:

endosymbiosis—the engulfment of another eukaryotic algae containing a red algal derived chloroplast. Others replaced their original chloroplast with a

6830: 2438:

and outermost two membranes, leaving just a two-membraned chloroplast. Cryptophyte chloroplasts require their nucleomorph to maintain themselves, and

447:

cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes. Like chloroplasts, they have

17857: 6597:, or ATP. Because chloroplast ATP synthase projects out into the stroma, the ATP is synthesized there, in position to be used in the dark reactions. 4553: 2066:

derived chloroplasts. Many other dinophytes have lost the chloroplast (becoming the nonphotosynthetic kind of dinoflagellate), or replaced it though

1503:

have been observed, probably because glaucophytes are relatively rare in nature, making them less likely to have been taken up by another eukaryote.

7655:

Light has been shown to be a requirement for chloroplast division. Chloroplasts can grow and progress through some of the constriction stages under

5032:

The number of thylakoids and the total thylakoid area of a chloroplast is influenced by light exposure. Shaded chloroplasts contain larger and more

1460: 11380:

Bernstein H, Bernstein C (July 1973). "Circular and branched circular concatenates as possible intermediates in bacteriophage T4 DNA replication".

4934:

known as frets or lamellar thylakoids. The helices ascend at an angle of ~20°, connecting to each granal thylakoid at a bridge-like slit junction.

2004:

pathway. This makes the apicoplast an attractive target for drugs to cure apicomplexan-related diseases. The most important apicoplast function is

12619: 7244: 5053:. The types of pigments found are different in various groups of chloroplasts, and are responsible for a wide variety of chloroplast colorations. 14506:"Microfilaments Anchor Chloroplasts along the Outer Periclinal Wall in Vallisneria Epidermal Cells through Cooperation of PFR and Photosynthesis" 14394:

Wells, C.; Balish, E. (1979). "The mitogenic activity of lipopolysaccharide for spleen cells from germfree, conventional, and gnotobiotic rats".

4925:

The three-dimensional structure of the thylakoid membrane system haz been disputed. Many models have been proposed, the most prevalent being the

2988: 1398: 765:. For these reasons, glaucophyte chloroplasts are considered a primitive intermediate between cyanobacteria and the more evolved chloroplasts in 16096: 7007:

In the presence of light, the pH of the thylakoid lumen can drop up to 1.5 pH units, while the pH of the stroma can rise by nearly one pH unit.

1743:

lineage. The chloroplast is surrounded by two membranes and has no nucleomorph—all the nucleomorph genes have been transferred to the dinophyte

5888:

evolved a way to solve this—by spatially separating the light reactions and the Calvin cycle. The light reactions, which store light energy in

10432:

Meeson BW, Chang SS, Sweeney BM (1982). "Characterization of Peridinin-Chlorophyll α-Proteins from the Marine Dinoflagellate Ceratium furca".

9327:"The evolution of glycogen and starch metabolism in eukaryotes gives molecular clues to understand the establishment of plastid endosymbiosis" 4268:

The inner chloroplast membrane borders the stroma and regulates passage of materials in and out of the chloroplast. After passing through the

4200:. However, there is a growing body of evidence that stromules are functional, integral features of plant cell plastids, not merely artifacts. 2434:. However, the cryptophyte is not an endosymbiont—only the chloroplast seems to have been taken, and the chloroplast has been stripped of its 16186: 13750:"The chloroplast import receptor Toc90 partially restores the accumulation of Toc159 client proteins in the Arabidopsis thaliana ppi2 mutant" 17850: 17714: 10478:"Phylogenetic analyses indicate that the 19'Hexanoyloxy-fucoxanthin-containing dinoflagellates have tertiary plastids of haptophyte origin" 9794: 7674:

Many mechanisms prevent biparental chloroplast DNA inheritance, including selective destruction of chloroplasts or their genes within the

14583:

Zeiger E, Talbott LD, Frechilla S, Srivastava A, Zhu J (2002). "The guard cell chloroplast: A perspective for the twenty-first century".

9303: 6447: 2173:, and have triplet-stacked thylakoids. Starch is found outside the chloroplast. An important feature of these chloroplasts is that their 1895:, triplet thylakoids, and with some exceptions, having four layer plastidic envelope, the outermost epiplastid membrane connected to the 1428:, forming a chloroplast with three or four membranes—the two cyanobacterial membranes, sometimes the eaten alga's cell membrane, and the 1174:

cells contain one or two sausage-shaped blue-green photosynthesizing structures called chromatophores, descended from the cyanobacterium

796: 5131:

pigment partially responsible for giving most cyanobacteria and chloroplasts their color. Other forms of chlorophyll exist, such as the

5001:

There are two types of thylakoids—granal thylakoids, which are arranged in grana, and stromal thylakoids, which are in contact with the

7652:

important. It is likely that chloroplast and cell division are somewhat synchronized, though the mechanisms for it are mostly unknown.

5989:

to transport stuff in and out of them. Mesophyll chloroplasts have a little more peripheral reticulum than bundle sheath chloroplasts.

1787:—outside the original double membrane, in the place that corresponds to the red alga's cytoplasm. Inside cryptophyte chloroplasts is a 606:

ancestor, and some descendants of it then engulfing the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria.

14731:"Fatty acid export from the chloroplast. Molecular characterization of a major plastidial acyl-coenzyme A synthetase from Arabidopsis" 13620: 11042:

Palmer JD, Thompson WF (June 1982). "Chloroplast DNA rearrangements are more frequent when a large inverted repeat sequence is lost".

10817: 662:

in this context means almost the same thing as chloroplast). All primary chloroplasts belong to one of four chloroplast lineages—the

8412:

Bryant DA, Guglielmi G, de Marsac NT, Castets AM, Cohen-Bazire G (1979). "The structure of cyanobacterial phycobilisomes: A model".

7469:

Almost all chloroplasts in a cell divide, rather than a small group of rapidly dividing chloroplasts. Chloroplasts have no definite

3665:

to many (but not all) of them in their transit sequences. Phosphorylation helps many proteins bind the polypeptide, keeping it from

17530: 4978:

that absorb light energy and use it to energize electrons. Molecules in the thylakoid membrane use the energized electrons to pump

6085:

cells can contain 30–70 chloroplasts per cell, while stomatal guard cells contain only around 8–15 per cell, as well as much less

6322:. The reactive oxygen species also directly kill any pathogens within the cell. Lower levels of reactive oxygen species initiate 241:

to reproduce. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts, like

7532: 7520: 6925: 6771:, in most plants, they take place in the light, since the dark reactions are dependent on the products of the light reactions. 4656:, though in mature chloroplasts, it is rare for a starch granule to be completely consumed or for a new granule to accumulate. 4494:, chloroplast translation is more complex than in bacteria, so chloroplast ribosomes include some chloroplast-unique features. 13749: 7351: 6634:, the enzyme that reduces NADP, releases the NADPH it makes into the stroma, right where it is needed for the dark reactions. 4394:

fluid within the inner chloroplast membrane and outside of the thylakoid space is called the stroma, which corresponds to the

3805:

All chloroplasts have at least three membrane systems—the outer chloroplast membrane, the inner chloroplast membrane, and the

3464:

Curiously, around half of the protein products of transferred genes aren't even targeted back to the chloroplast. Many became

14810: 14361: 14336: 14260: 14052: 13430: 12942: 12533: 12495: 12336: 12126: 11445:

Huang CY, Ayliffe MA, Timmis JN (March 2003). "Direct measurement of the transfer rate of chloroplast DNA into the nucleus".

11101: 10867: 9500: 9297: 8388: 8258: 8001: 6791:(RuBP) molecules. The result is unstable six-carbon molecules that immediately break down into three-carbon molecules called 16154: 15066:"Stimulation by Light of Rapid pH Regulation in the Chloroplast Stroma in Vivo as Indicated by CO2 Solubilization in Leaves" 10109:

Hackett JD, Anderson DM, Erdner DL, Bhattacharya D (October 2004). "Dinoflagellates: a remarkable evolutionary experiment".

3230:. Hypoxanthine can bind to cytosine, and when the XC base pair is replicated, it becomes a GC (thus, an A → G base change). 3066:

While usually thought of as a circular molecule, there is some evidence that chloroplast DNA molecules more often take on a

1988:

chloroplasts provide plant cells with many important things besides sugar, and apicoplasts are no different—they synthesize

13156:"Correlations between Shine-Dalgarno sequences and gene features such as predicted expression levels and operon structures" 12633:

Gray JC, Sullivan JA, Hibberd JM, Hansen MR (2001). "Stromules: mobile protrusions and interconnections between plastids".

7636:

chloroplasts, many dumbbell-shaped chloroplasts can be seen dividing. Grana are also just barely visible as small granules.

7599:

chloroplasts, some dumbbell-shaped chloroplasts can be seen dividing. Grana are also just barely visible as small granules.

7586:

chloroplasts, some dumbbell-shaped chloroplasts can be seen dividing. Grana are also just barely visible as small granules.

3813:

may have additional membranes surrounding these three. Inside the outer and inner chloroplast membranes is the chloroplast

3120:, which can contain several identical chloroplast DNA rings. Many nucleoids can be found in each chloroplast. In primitive 11174:"MSH1 maintains organelle genome stability and genetically interacts with RECA and RECG in the moss Physcomitrella patens" 5858:, so at high oxygen concentrations, RuBisCO starts accidentally adding oxygen to sugar precursors. This has the result of 3422: with: Genome size differences between algae and land plants, chloroplast stuff coded by the nucleus. You can help by 3210:

mechanisms. Adapted from Krishnan NM, Rao BJ's paper "A comparative approach to elucidate chloroplast genome replication."

15193:"Integral membrane proteins of the chloroplast envelope: identification and subcellular localization of new transporters" 14139: 12551:"Polypeptide composition of envelopes of spinach chloroplasts: two major proteins occupy 90% of outer envelope membranes" 8371:

Kim E, Archibald JM (2009). "Diversity and Evolution of Plastids and Their Genomes". In Sandelius AS, Aronsson H (eds.).

6354: 3190:

protein maintains the integrity of the chloroplast's DNA by a process that likely involves the recombinational repair of

3262:

The chloroplast genome most commonly includes around 100 genes that code for a variety of things, mostly to do with the

1546:, but unlike chloroplasts in their green algal ancestors, storage product collects in granules outside the chloroplast. 1038:

chloroplasts, are another large, highly diverse primary chloroplast lineage. Their host organisms are commonly known as

577:, or "cell living inside another cell with a mutual benefit for both". The external cell is commonly referred to as the 7368:

Plastid differentiation is not permanent, in fact many interconversions are possible. Chloroplasts may be converted to

7242: 4637:

are very common in chloroplasts, typically taking up 15% of the organelle's volume, though in some other plastids like

14379:

Lawson T. and J. I. L. Morison. Essay 10.1 Guard Cell Photosynthesis. Plant Physiology and Development, Sixth Edition

13833:"The three-dimensional network of the thylakoid membranes in plants: quasihelical model of the granum-stroma assembly" 11967:

Hedtke B, Börner T, Weihe A (August 1997). "Mitochondrial and chloroplast phage-type RNA polymerases in Arabidopsis".

9690:"The non-photosynthetic, pathogenic green alga Helicosporidium sp. has retained a modified, functional plastid genome" 7443:

Most chloroplasts in a photosynthetic cell do not develop directly from proplastids or etioplasts. In fact, a typical

5958:

stacks—though bundle sheath chloroplasts still have free-floating thylakoids in the stroma where they still carry out

261:

cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division.

17720: 16179: 15912:"Polymorphic simple sequence repeat regions in chloroplast genomes: applications to the population genetics of pines" 15587: 15560: 15524: 15175: 14933: 14901: 14633:"All hands on deck—the role of chloroplasts, endoplasmic reticulum, and the nucleus in driving plant innate immunity" 13969:"Three-dimensional architecture of grana and stroma thylakoids of higher plants as determined by electron tomography" 13474: 12863: 11429: 10897: 8061: 7957: 7930: 7779: 7235: 1067:, due to accessory pigments that override the chlorophylls' green colors. Chloroplastida chloroplasts have lost the 16615: 14278:"Ultrastructure of Chloroplast Membranes in Leaves of Maize and Ryegrass as Revealed by Selective Staining Methods" 7166:. Pyruvate is also made in the plastid from phosphoenolpyruvate, a metabolite made in the cytosol from pyruvate or 5982: 5005:. Granal thylakoids are pancake-shaped circular disks about 300–600 nanometers in diameter. Stromal thylakoids are 4919: 4322: 3856: 3836: 3736: 3191: 1868:, also known as the stramenopiles, are a very large and diverse group of eukaryotes. The photoautotrophic lineage, 1123: 6574:

between the photosystems harness the electrons' energy to pump hydrogen ions into the thylakoid space, creating a

17054: 16248: 11413: 11411: 8021: 6631: 5009:

sheets that spiral around grana. The flat tops and bottoms of granal thylakoids contain only the relatively flat

3721: 3340: 2967: 15369:

Buchanan BB, Gruissem W, Jones RL (Eds.). 2015. Biochemistry & Molecular Biology of Plants. Wiley Blackwell.

13917:"Three-dimensional organization of higher-plant chloroplast thylakoid membranes revealed by electron tomography" 11704: 7162:. Pyruvate may enter the plastid from the cytosol by passive diffusion through the membrane after production in 5325:, are also common. Many other forms of carotenoids exist that are only found in certain groups of chloroplasts. 3835: 3817:, a semi-gel-like fluid that makes up much of a chloroplast's volume, and in which the thylakoid system floats. 18518: 18113: 17535: 11325: 7886: 7870: 7527:

manages the placement of the Z-ring, ensuring that the chloroplast is cleaved more or less evenly. The protein

5381:

Table of the presence of various pigments across chloroplast groups. Colored cells represent pigment presence.

4784: 4344:. The chloroplast peripheral reticulum consists of a maze of membranous tubes and vesicles continuous with the 4028: 4024: 372: 322: 279: 201:

in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like

13584:

Retallack B, Butler RD (January 1970). "The development and structure of pyrenoids in Bulbochaete hiloensis".

11408: 7830: 7706:, which pass on chloroplasts maternally, have many ways to prevent paternal inheritance. Most of them produce 7241: 7239: 6637:

Because NADP reduction removes electrons from the electron transport chains, they must be replaced—the job of

6398:, the process by which light is transformed into chemical energy, to subsequently produce food in the form of 470:

attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though).

18692: 18654: 16985: 16350: 14016: 12879:

Plant peptidoglycan precursor biosynthesis: Conservation between moss chloroplasts and Gram-negative bacteria

9738:"Endosymbiotic gene transfer and transcriptional regulation of transferred genes in Paulinella chromatophora" 7240: 7237: 7232: 7024: 3332: 345:

Chloroplasts are one of many types of organelles in the plant cell. They are considered to have evolved from

283: 15255:"Subcellular Distribution of O-Acetylserine(thiol)lyase in Cauliflower (Brassica oleracea L.) Inflorescence" 12487:

The freshwater algal flora of the British Isles: an identification guide to freshwater and terrestrial algae

7236: 6065:

of leaf tissue can contain half a million chloroplasts. Within a leaf, chloroplasts are mainly found in the

4611:

chloroplasts, plastoglobuli tend to occur in linked groups or chains, still always anchored to a thylakoid.

1806:

which they keep in their thylakoid space, rather than anchored on the outside of their thylakoid membranes.

874:

chloroplast group is another large and diverse chloroplast lineage. Rhodophyte chloroplasts are also called

18302: 17983: 17704: 17291: 16806: 16172: 13534:"Identification of a novel gene, CIA6, required for normal pyrenoid formation in Chlamydomonas reinhardtii" 7234: 7233: 7231: 6929: 6853:

commonly known as table sugar, is made, though this process takes place outside of the chloroplast, in the

6323: 6311: 5986: 4914:, it became possible to see the thylakoid system in more detail, revealing it to consist of stacks of flat 4353: 4189: 3346:

In land plants, some 11–14% of the DNA in their nuclei can be traced back to the chloroplast, up to 18% in

2233:) lost their original red algal derived chloroplast, and replaced it with a new chloroplast derived from a 1816: 17: 17988: 15606:

Possingham JV, Rose RJ (1976). "Chloroplast Replication and Chloroplast DNA Synthesis in Spinach Leaves".

15191:

Ferro M, Salvi D, Riviere-Rolland H, Vermat T, Seigneurin-Berny D, Grunwald D, et al. (August 2002).

11125:"Detection and localization of a chloroplast-encoded HU-like protein that organizes chloroplast nucleoids" 10655:

Stocking, C. R. & Gifford, E. M. (1959). "Incorporation of thymidine into chloroplasts of Spirogyra".

9208: 7229: 6236: with: determined functions, controversial functions, characteristics and population. You can help by 4918:

which made up the grana, and long interconnecting stromal thylakoids which linked different grana. In the

4525:

and prokaryotes. An additional 4.5S rRNA with homology to the 3' tail of 23S is found in "higher" plants.

4045:

Chloroplasts have at least three distinct membrane systems, and a variety of things can be found in their

3124:, the chloroplast DNA nucleoids are clustered in the center of the chloroplast, while in green plants and 3059:

long. They can have a contour length of around 30–60 micrometers, and have a mass of about 80–130 million

2273:) and no peridinin. Fucoxanthin is also found in haptophyte chloroplasts, providing evidence of ancestry. 18222: 17978: 17786: 17540: 10473: 7835: 7668: 7455:, chloroplast division provides the additional chloroplasts to partition between the two daughter cells. 6680: 6662: 6299:

defense. Due to its role in a plant cell's immune response, pathogens frequently target the chloroplast.

3307: 2477: 2344: 1776: 1476:

The genes in the phagocytosed eukaryote's nucleus are often transferred to the secondary host's nucleus.

237:

Chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally

7318:

shoots are not exposed to the required light for chloroplast formation, proplastids may develop into an

7238: 17520: 15761:"Effect of light on the chloroplast division cycle and DNA synthesis in cultured leaf discs of spinach" 12591: 10161:

Bodył A (February 2018). "Did some red alga-derived plastids evolve via kleptoplastidy? A hypothesis".

7767: 7727: 7423: with: functions, Z-ring dynamic assembly, regulators such as Giant Chloroplast 1. You can help by 6990: 6869: 6804: 6753: 5949:. The four-carbon compound is then transported to the bundle sheath chloroplasts, where it drops off CO 4967: 4438: 4345: 4016: 3908: 3888: 2680: 2652: 618:

600–2000 million years ago. It has been proposed this the closest living relative of this bacterium is

420:

Chloroplasts are considered endosymbiotic Cyanobacteria. Cyanobacteria are sometimes called blue-green

15003:

Carmi A, Shomer I (1979). "Starch Accumulation and Photosynthetic Activity in Primary Leaves of Bean (

7230: 5828:. The two types of cells contain different types of chloroplasts specialized for a particular part of 4564:. Plastoglobuli also exhibit a greater size variation under these conditions. They are also common in 18523: 17670: 15667: 13880:

Paolillo Jr, DJ (1970). "The three-dimensional arrangement of intergranal lamellae in chloroplasts".

6615: 6442:, which builds sugar molecules from carbon dioxide. The two phases are linked by the energy carriers 6155:

or turning sideways so that light strikes them edge-on. This reduces exposure and protects them from

4467: 4090: 3629: 2005: 1993: 1128: 620: 7554:, chloroplasts have a third plastid-dividing ring located in the chloroplast's intermembrane space. 7550: 7481: 6985:, which can disturb the pH of isolated chloroplasts, interfering with photosynthesis, even though CO 4556:. Plastoglobuli are found in all chloroplasts, but become more common when the chloroplast is under 4101:

to it is the internal thylakoid system. Even so, in terms of "in-out", the direction of chloroplast

1063: 18370: 18271: 18188: 17808: 17653: 16703: 16345: 12847: 12845: 12843: 12841: 12839: 12837: 12835: 12833: 12831: 12829: 9024:

Ponce-Toledo RI, Deschamps P, López-García P, Zivanovic Y, Benzerara K, Moreira D (February 2017).

8017: 6567: 4066:. This is often interpreted as meaning the outer chloroplast membrane is the product of the host's 3544: 3379: 3247: 3246:

One of competing model for cpDNA replication asserts that most cpDNA is linear and participates in

3166: 3019: 2245: 2229: 1841:

sugar, which they store completely outside of the chloroplast, in the cytoplasm of the haptophyte.

368: 138: 15707:

Miyagishima SY, Nishida K, Mori T, Matsuzaki M, Higashiyama T, Kuroiwa H, Kuroiwa T (March 2003).

10207:

Janouškovec J, Gavelis GS, Burki F, Dinh D, Bachvaroff TR, Gornik SG, et al. (January 2017).

7424: 7131: 6237: 3423: 54: 18682: 18397: 18173: 15516: 13466: 7171: 6349: 6319: 6315: 6303: 5904:

leaf. The Calvin cycle, which uses the stored energy to make sugar using RuBisCO, is done in the

5184: 4510: 4239: 3676:

From here, chloroplast proteins bound for the stroma must pass through two protein complexes—the

3524:. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway. 2462:

species must continually engulf cryptophytes to obtain new chloroplasts to replace the old ones.

2078: 647:

These chloroplasts, which can be traced back directly to a cyanobacterial ancestor, are known as

15544: 15542: 15540: 15538: 15536: 15159: 15157: 15155: 15153: 15151: 15149: 15147: 12826: 12727:"Differential coloring reveals that plastids do not form networks for exchanging macromolecules" 8822: 8045: 8043: 8041: 8039: 6264:

contain relatively well-developed chloroplasts. However, exactly what they do is controversial.

3222:

In addition to the early microscopy experiments, this model is also supported by the amounts of

18625: 17941: 17638: 17562: 16310: 16285: 15662: 14956:"Effect of Flooding on Starch Accumulation in Chloroplasts of Sunflower (Helianthus annuus L.)" 13272: 12462: 12440: 12418: 12396: 12374: 12352: 11562:"A plastid without a genome: evidence from the nonphotosynthetic green algal genus Polytomella" 11123:

Kobayashi T, Takahara M, Miyagishima SY, Kuroiwa H, Sasaki N, Ohta N, et al. (July 2002).

9785: 7850: 7743: 7739: 7292: 7186: 7167: 6920:. This process reduces the efficiency of photosynthesis—it consumes ATP and oxygen, releases CO 6796: 6792: 6757: 6692: 6594: 6575: 6511: 6495: 6443: 5963: 5889: 5859: 5368:, phycobilisomes jut into the stroma, preventing thylakoid stacking in red algal chloroplasts. 5046: 4995: 4991: 4094: 4085:

double membrane. This is not a valid comparison—the inner mitochondria membrane is used to run

3732: 2552: 452: 433: 170: 60: 17367: 13420: 13014:"The complete structure of the chloroplast 70S ribosome in complex with translation factor pY" 12895:"The occurrence of a peripheral reticulum in plastids of the gymnosperm Welwitschia mirabilis" 12485: 9582:"Genes for the peptidoglycan synthesis pathway are essential for chloroplast division in moss" 7326:, and has inner membrane invaginations that form a lattice of tubes in their stroma, called a 1775:. Cryptophyte chloroplasts have four membranes, the outermost of which is continuous with the 18385: 18358: 17973: 17803: 16549: 16335: 16228: 15577: 15550: 15533: 15184: 15165: 15144: 14326: 12932: 12853: 10887: 10857: 8036: 7331: 7004:

and H ions in and out of themselves using a poorly understood light-driven transport system.

6788: 6590: 6521: 6307: 6292: 6280: 6171: 6123: 4514: 4487: 4197: 4193: 3624: 3458: 3448: 3383: 3157: 2328: 1977: 1896: 1821: 1014: 17961: 16159: 13107:"Functional Shine-Dalgarno-like sequences for translational initiation of chloroplast mRNAs" 12878: 10324:

Quigg A, Kotabová E, Jarešová J, Kaňa R, Setlík J, Sedivá B, et al. (10 October 2012).

9641:"How Do algae concentrate CO2 to increase the efficiency of photosynthetic carbon fixation?" 7396:

is illuminated. If a plant is injured, or something else causes a plant cell to revert to a

6764:

made in the light reactions. The Calvin cycle takes place in the stroma of the chloroplast.

4301:

In addition to regulating the passage of materials, the inner chloroplast membrane is where

4246:

ancestors, which is located between their two cell membranes. These chloroplasts are called

829: 18329: 18324: 18200: 17525: 17422: 17377: 17049: 16608: 16582: 16115: 16047: 15985: 15923: 15864: 15615: 15315: 15204: 14839: 14685: 13702: 13651: 12787: 12642: 11855: 11737: 11667: 11622: 11514: 11454: 10993: 10775: 10609: 10535: 10385:"Do red and green make brown?: perspectives on plastid acquisitions within chromalveolates" 10337: 10220: 9999: 9833: 9593: 9146: 9094: 9037: 8980: 8686: 8587: 8421: 8090: 7656: 7206: 6541: 6195: 5959: 5256: 5064: 4659:

Starch granules vary in composition and location across different chloroplast lineages. In

4649: 4263: 4115: 4056: 3877: 3481: 3366: 3182: 2281: 1997: 598: 499: 215: 190: 17025: 15853:"Uniparental inheritance of mitochondrial and chloroplast genes: mechanisms and evolution" 14596: 13412: 12725:

Schattat MH, Griffiths S, Mathur N, Barton K, Wozny MR, Dunn N, et al. (April 2012).

11844:"Evolution of chloroplast retrograde signaling facilitates green plant adaptation to land" 11501:

Martin W, Rujan T, Richly E, Hansen A, Cornelsen S, Lins T, et al. (September 2002).

11093: 10821: 10494: 10477: 1809:

Cryptophytes may have played a key role in the spreading of red algal based chloroplasts.

8: 18565: 18407: 18363: 18319: 18057: 17695: 17240: 16208: 8725: 8641: 7816: 7795: 6042:

cells. Stomal guard cells also have chloroplasts, though much fewer than mesophyll cells.

5905: 5821: 4911: 4700: 4491: 3898: 3521: 3397: 3215: 3162: 3083: 1772: 1624: 1180:. Chromatophores cannot survive outside their host. Chromatophore DNA is about a million 924:, which collects into granules outside the rhodoplast, in the cytoplasm of the red alga. 275: 16119: 16051: 15989: 15927: 15868: 15709:"A plant-specific dynamin-related protein forms a ring at the chloroplast division site" 15619: 15319: 15208: 14843: 14689: 14216: 14173:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

13706: 12791: 12646: 12071: 11944: 11911: 11859: 11741: 11671: 11626: 11518: 11458: 10997: 10779: 10613: 10539: 10341: 10224: 10003: 9837: 9597: 9435:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

9150: 9098: 9041: 8984: 8690: 8591: 8425: 8139:"An Expanded Ribosomal Phylogeny of Cyanobacteria Supports a Deep Placement of Plastids" 8094: 7730:. Since, in most flowering plants, chloroplasts are not inherited from the male parent, 4922:, thylakoid membranes appear as alternating light-and-dark bands, 8.5 nanometers thick. 1451:

being engulfed by another eukaryote, forming a chloroplast with three or four membranes.

1079:

for the synthesis of the peptidoglycan layer, though they've been repurposed for use in

732: 18615: 17633: 17498: 17276: 16968: 16754: 16650: 16070: 16035: 15785: 15760: 15631: 15509: 15432: 15415: 15279: 15254: 15020: 14980: 14955: 14706: 14673: 14522: 14505: 14483: 14299: 14294: 14277: 14193: 14168: 14115: 14088: 14068: 13993: 13968: 13941: 13916: 13857: 13832: 13725: 13690: 13643: 13639: 13558: 13533: 13459: 13401: 13353: 13328: 13301: 13276: 13229: 13204: 13136: 13038: 13013: 12986: 12959: 12911: 12894: 12810: 12776:"Chloroplasts extend stromules independently and in response to internal redox signals" 12775: 12751: 12726: 12702: 12677: 12658: 12567: 12550: 12237:"14-3-3 proteins form a guidance complex with chloroplast precursor proteins in plants" 12168: 12143: 12099: 11886: 11843: 11823: 11768: 11725: 11691: 11586: 11561: 11478: 11301: 11274: 11239: 11214: 11067: 10799: 10708: 10683: 10632: 10597: 10449: 10409: 10384: 10360: 10325: 10301: 10274: 10243: 10208: 10186: 10023: 9962: 9916: 9665: 9640: 9616: 9581: 9455: 9430: 9218: 9191: 9167: 9134: 9058: 9025: 9006: 8944: 8919: 8886: 8859: 8799: 8782: 8709: 8674: 8613: 8549: 8437: 8394: 8217: 8192: 8165: 8138: 8111: 8078: 7444: 7277: 6961: 6933: 6623: 6551: 6106: 6082: 5940: 5791: 5547: 5132: 4718:

The chloroplast stroma contains many proteins, though the most common and important is

4361: 4217: 4075: 3938: 3654: 3477: 3097: 2995: 2974: 2960: 2939: 2918: 2785: 2771: 2729: 2638: 2631: 2608: 2255: 1885: 1542:) in three or four separate engulfments. Many green algal derived chloroplasts contain 1519: 1481: 1429: 1311: 1046:. They differ from glaucophyte and red algal chloroplasts in that they have lost their 822: 558:

Separately, somewhere about 90–140 million years ago, it happened again and led to the

533: 511: 367:

was engulfed. This origin of chloroplasts was first suggested by the Russian biologist

330: 181:

from water in the cells. The ATP and NADPH is then used to make organic molecules from

17842: 16164: 16008: 15973: 15754: 15752: 15733: 15708: 15569: 15484: 15457: 15227: 15192: 15090: 15065: 14862: 14827: 14755: 14730: 13790: 13180: 13155: 12302: 12285: 12261: 12236: 12028: 12003: 11794:"The Chara Genome: Secondary Complexity and Implications for Plant Terrestrialization" 11537: 11502: 11149: 11124: 11016: 10981: 10952: 10927: 9580:

Machida M, Takechi K, Sato H, Chung SJ, Kuroiwa H, Takio S, et al. (April 2006).

8758: 8733: 2518:, and other algal groups are extremely underrepresented, potentially introducing some 1973:

granules that are located in their cytoplasm, even though they are nonphotosynthetic.

1595:, which is contained in membrane-bound granules in the cytoplasm of the euglenophyte. 18687: 18610: 18314: 17791: 16640: 16635: 16532: 16370: 16253: 16143: 16138: 16103: 16075: 16013: 15951: 15946: 15911: 15892: 15887: 15852: 15833: 15790: 15738: 15583: 15556: 15520: 15489: 15396: 15343: 15338: 15303: 15284: 15232: 15171: 15133: 15129: 15095: 14985: 14929: 14922: 14897: 14890: 14867: 14806: 14760: 14711: 14654: 14600: 14565: 14475: 14470: 14453: 14411: 14357: 14332: 14307: 14256: 14198: 14120: 14048: 13998: 13946: 13897: 13862: 13772: 13730: 13601: 13563: 13511: 13470: 13426: 13393: 13358: 13306: 13234: 13185: 13171: 13128: 13087: 13043: 12991: 12938: 12859: 12815: 12756: 12707: 12678:"Plastid stromule branching coincides with contiguous endoplasmic reticulum dynamics" 12611: 12572: 12529: 12491: 12332: 12307: 12266: 12214: 12173: 12122: 12091: 12033: 11984: 11949: 11931: 11891: 11873: 11827: 11815: 11773: 11755: 11724:

de Vries, Jan; Curtis, Bruce A.; Gould, Sven B.; Archibald, John M. (10 April 2018).

11695: 11683: 11640: 11591: 11542: 11470: 11425: 11397: 11393: 11306: 11244: 11195: 11154: 11097: 11059: 11055: 11021: 10957: 10893: 10863: 10791: 10748: 10744: 10713: 10668: 10637: 10499: 10414: 10365: 10306: 10248: 10178: 10126: 10064: 10015: 9984: 9954: 9908: 9861: 9856: 9821: 9759: 9711: 9670: 9621: 9562: 9496: 9460: 9348: 9293: 9223: 9172: 9112: 9063: 8998: 8949: 8891: 8804: 8763: 8714: 8605: 8541: 8384: 8254: 8222: 8170: 8116: 8057: 7997: 7953: 7926: 7775: 4947: 4796: 4352:

fluid of the chloroplast. Its purpose is thought to be to increase the chloroplast's

4231: 4213: 4098: 3954: 3948: 3497: 3357: 3287: 3263: 3036: 3009: 2932: 2904: 2841: 2820: 2673: 2374: 2187: 1865: 16036:"Determining the transgene containment level provided by chloroplast transformation" 14352:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

14251:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

14043:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

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Bussi Y; Shimoni E; Weiner A; Kapon R; Charuvi D; Nevo R; Efrati E; Reich Z (2019).

13647: 13405: 13140: 12662: 12592:"Plastid tubules of higher plants are tissue-specific and developmentally regulated" 12524:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

12117:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

12103: 11071: 10453: 10190: 10027: 9983:

Moustafa A, Beszteri B, Maier UG, Bowler C, Valentin K, Bhattacharya D (June 2009).

9966: 9920: 9491:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

8617: 8553: 8398: 8249:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

7992:

Campbell NA, Reece JB, Urry LA, Cain ML, Wasserman, Minorsky PV, Jackson RB (2009).

6329:

In some plants, chloroplasts are known to move closer to the infection site and the

4870:

chloroplasts, the thylakoids are arranged in stacks called grana, though in certain

889:

on the thylakoid membranes, preventing their thylakoids from stacking. Some contain

18346: 18240: 17873: 17577: 17483: 17478: 17432: 17325: 17310: 17271: 17196: 17037: 16961: 16858: 16800: 16133: 16123: 16065: 16055: 16003: 15993: 15941: 15931: 15882: 15872: 15825: 15780: 15772: 15749: 15728: 15720: 15672: 15635: 15623: 15479: 15469: 15427: 15388: 15333: 15323: 15274: 15266: 15222: 15212: 15125: 15085: 15077: 15016: 14975: 14967: 14928:(5. ed., 4. print. ed.). New York, NY : W. H. Freeman. pp. Section 20.1. 14896:(5. ed., 4. print. ed.). New York, NY : W. H. Freeman. pp. Section 19.4. 14857: 14847: 14750: 14742: 14701: 14693: 14644: 14592: 14555: 14517: 14487: 14465: 14403: 14289: 14188: 14180: 14110: 14100: 13988: 13980: 13936: 13928: 13889: 13852: 13844: 13764: 13720: 13710: 13635: 13593: 13553: 13545: 13503: 13385: 13348: 13340: 13322: 13320: 13296: 13288: 13224: 13216: 13175: 13167: 13118: 13077: 13033: 13025: 12981: 12971: 12906: 12805: 12795: 12746: 12738: 12697: 12689: 12650: 12603: 12562: 12297: 12256: 12248: 12204: 12163: 12155: 12083: 12023: 12019: 12015: 11976: 11939: 11923: 11881: 11863: 11805: 11763: 11745: 11675: 11630: 11581: 11573: 11532: 11522: 11482: 11462: 11389: 11337: 11296: 11286: 11234: 11226: 11185: 11144: 11136: 11051: 11011: 11001: 10947: 10939: 10803: 10783: 10740: 10703: 10695: 10664: 10627: 10617: 10576: 10543: 10489: 10441: 10404: 10396: 10355: 10345: 10296: 10286: 10238: 10228: 10170: 10118: 10054: 10007: 9946: 9900: 9851: 9841: 9749: 9701: 9660: 9652: 9611: 9601: 9554: 9450: 9442: 9338: 9213: 9203: 9162: 9154: 9102: 9053: 9045: 8988: 8939: 8931: 8881: 8871: 8794: 8753: 8745: 8704: 8694: 8595: 8531: 8441: 8429: 8376: 8212: 8204: 8160: 8150: 8106: 8098: 7715: 7629: 7327: 7068: 6905: 6547: 6039: 5897: 5817: 4998:

energy as the hydrogen ions flow back out into the stroma—much like a dam turbine.

4903: 4676: 4644:

Starch granules appear and grow throughout the day, as the chloroplast synthesizes

4557: 4192:

for cross-membrane transport, because they are often branched and tangled with the

3964: 3328: 3312: 3251: 2352: 2315: 2300: 2178: 1629: 1335: 921: 361: 78: 17372: 15392: 13748:

Infanger S, Bischof S, Hiltbrunner A, Agne B, Baginsky S, Kessler F (March 2011).

10326:"Photosynthesis in Chromera velia represents a simple system with high efficiency" 9736:

Nowack EC, Vogel H, Groth M, Grossman AR, Melkonian M, Glöckner G (January 2011).

9545:

Lewis LA, McCourt RM (October 2004). "Green algae and the origin of land plants".

8024:[About the nature and origin of chromatophores in the vegetable kingdom]. 4791:

is found in the pyrenoids. Starch can also accumulate around the pyrenoids when CO

4120:

The outer chloroplast membrane is a semi-porous membrane that small molecules and

1891:

Heterokont chloroplasts are very similar to haptophyte chloroplasts, containing a

1216: 836: 503: 18603: 18297: 18276: 18205: 18008: 17831: 17813: 17675: 17504: 17454: 17442: 17404: 17340: 17167: 17135: 17096: 17069: 16898: 16893: 16784: 16720: 16601: 16233: 14949: 14947: 14945: 14269: 12976: 12960:"Structure of the chloroplast ribosome: novel domains for translation regulation" 12326: 11980: 11086: 10350: 10291: 9731: 9729: 9727: 9725: 9706: 9689: 9010: 7947: 7918: 7800: 7703: 7693: 7273: 6582:

back down their concentration gradient, flowing back out into the stroma through

6468: 6459: 6431: 6358: 6200: 6187: 5871: 5290: 4951: 4859: 4832: 4704: 4634: 4572: 4483: 4407: 3928: 3792:. In some algae, the chloroplast takes up most of the cell, with pockets for the 3786: 3666: 3662: 3473: 3361: 2495: 2471: 2174: 2044: 1965: 1900: 1838: 1812: 1698: 1139: 752: 693: 689: 681: 637: 198: 16392: 13317: 12888: 12886: 11912:"Environmental gradients reveal stress hubs pre-dating plant terrestrialization" 11651: 10598:"Integration of plastids with their hosts: Lessons learned from dinoflagellates" 10209:"Major transitions in dinoflagellate evolution unveiled by phylotranscriptomics" 10145: 8380: 8208: 6141: 6137: 5866:

being released, all with no sugar being produced. This is a big problem, since O

5212:, although it is not found in chloroplasts of red algae themselves. Chlorophyll 5045:

Inside the photosystems embedded in chloroplast thylakoid membranes are various

4188:

in petals and roots, respectively. They may exist to increase the chloroplast's

3755:, which often contain a single chloroplast that can be shaped like a net (e.g., 3250:

and replication structures similar to the linear and circular DNA structures of

3233: 1197:

is from the chromatophore, compared with 11–14% from the chloroplast in plants.

18593: 18480: 18351: 18210: 18193: 17998: 17928: 17725: 17690: 17643: 17625: 17589: 17345: 17172: 17150: 17116: 17091: 17074: 17064: 17059: 16941: 16759: 16744: 16698: 16693: 16196: 16108: