In cell biology , an organelle is a specialized subunit, usually within a cell , that has a specific function. The name organelle comes from the idea that these structures are parts of cells, as organs are to the body , hence organelle, the suffix -elle being a diminutive . Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bounded organelles) or are spatially distinct functional units without a surrounding lipid bilayer (non-membrane bounded organelles). Although most organelles are functional units within cells, some function units that extend outside of cells are often termed organelles, such as cilia , the flagellum and archaellum , and the trichocyst (these could be referred to as membrane bound in the sense that they are attached to (or bound to) the membrane).
60-414: L -α-Glycerophosphorylcholine ( alpha-GPC , choline alfoscerate , sn -glycero-3-phosphocholine ) is a natural choline compound found in the brain. It is also a parasympathomimetic acetylcholine precursor which has been investigated for its potential for the treatment of Alzheimer's disease and other dementias . Alpha-GPC rapidly delivers choline to the brain across the blood–brain barrier and
120-436: A family of water-soluble quaternary ammonium compounds . Choline is the parent compound of the cholines class, consisting of ethanolamine residue having three methyl groups attached to the same nitrogen atom. Choline hydroxide is known as choline base. It is hygroscopic and thus often encountered as a colorless viscous hydrated syrup that smells of trimethylamine (TMA). Aqueous solutions of choline are stable, but
180-475: A footnote, which was published as a correction in the next issue of the journal, he justified his suggestion to call organs of unicellular organisms "organella" since they are only differently formed parts of one cell, in contrast to multicellular organs of multicellular organisms. While most cell biologists consider the term organelle to be synonymous with cell compartment , a space often bounded by one or two lipid bilayers, some cell biologists choose to limit
240-486: A precursor for other essential cell components and signaling molecules, such as phospholipids that form cell membranes, the neurotransmitter acetylcholine, and the osmoregulator trimethylglycine ( betaine ). Trimethylglycine in turn serves as a source of methyl groups by participating in the biosynthesis of S -adenosylmethionine . Choline is transformed to diverse phospholipids, like phosphatidylcholines and sphingomyelins. These are found in all cell membranes and
300-585: A shell of proteins. Even more striking is the description of membrane-bounded magnetosomes in bacteria, reported in 2006. The bacterial phylum Planctomycetota has revealed a number of compartmentalization features. The Planctomycetota cell plan includes intracytoplasmic membranes that separates the cytoplasm into paryphoplasm (an outer ribosome-free space) and pirellulosome (or riboplasm, an inner ribosome-containing space). Membrane-bounded anammoxosomes have been discovered in five Planctomycetota "anammox" genera, which perform anaerobic ammonium oxidation . In
360-679: A side product. In humans and most other animals, de novo synthesis of choline proceeds via the phosphatidylethanolamine N-methyltransferase (PEMT) pathway, but biosynthesis is not enough to meet human requirements. In the hepatic PEMT route, 3-phosphoglycerate (3PG) receives 2 acyl groups from acyl-CoA forming a phosphatidic acid . It reacts with cytidine triphosphate to form cytidine diphosphate-diacylglycerol. Its hydroxyl group reacts with serine to form phosphatidylserine which decarboxylates to ethanolamine and phosphatidylethanolamine (PE) forms. A PEMT enzyme moves three methyl groups from three S -adenosyl methionines (SAM) donors to
420-452: Is oxidized irreversibly in liver mitochondria to glycine betaine aldehyde by choline oxidases . This is oxidized by mitochondrial or cytosolic betaine-aldehyde dehydrogenases to trimethylglycine. Trimethylglycine is a necessary osmoregulator. It also works as a substrate for the BHMT -enzyme, which methylates homocysteine to methionine . This is a S -adenosylmethionine (SAM) precursor. SAM
480-459: Is 550 mg for adults and children age 4 years and older. The FDA does not require food labels to list choline content unless choline has been added to the food. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet. The U.S. Department of Agriculture's (USDA's) FoodData Central lists
540-454: Is 7–20 micromoles per liter (μmol/L) and 10 μmol/L on average. Levels are regulated, but choline intake and deficiency alters these levels. Levels are elevated for about 3 hours after choline consumption. Phosphatidylcholine levels in the plasma of fasting adults is 1.5–2.5 mmol/L. Its consumption elevates the free choline levels for about 8–12 hours, but does not affect phosphatidylcholine levels significantly. Choline
600-584: Is a biosynthetic precursor of acetylcholine . It is a non-prescription drug in most countries. The FDA determined that intake of no more than 196.2 mg/person/day is considered generally recognized as safe (GRAS). Industrially, alpha-GPC is produced by the chemical or enzymatic deacylation of phosphatidylcholine enriched soya phospholipids followed by chromatographic purification . Alpha-GPC may also be derived in small amounts from highly purified soy lecithin as well as from purified sunflower lecithin. Alpha-GPC metabolizes to trimethylamine n-oxide in
660-429: Is a common reagent in biological methylation reactions. For example, it methylates guanidines of DNA and certain lysines of histones . Thus it is part of gene expression and epigenetic regulation . Choline deficiency thus leads to elevated homocysteine levels and decreased SAM levels in blood. Choline occurs in foods as a free cation and in the form of phospholipids, especially as phosphatidylcholines. Choline
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#1733085303554720-415: Is a structural part of phospholipids and cell membranes . Choline is used to synthesize acetylcholine , a neurotransmitter involved in muscle control and numerous functions of the nervous system. Choline is involved in early development of the brain, gene expression , cell membrane signaling , and brain metabolism. Although humans synthesize choline in the liver , the amount produced naturally
780-421: Is a water-soluble ion and thus requires transporters to pass through fat-soluble cell membranes . Three types of choline transporters are known: SLC5A7s are sodium - (Na ) and ATP-dependent transporters. They have high binding affinity for choline, transport it primarily to neurons and are indirectly associated with the acetylcholine production. Their deficient function causes hereditary weakness in
840-462: Is an essential nutrient for humans and many other animals. Humans are capable of some de novo synthesis of choline but require additional choline in the diet to maintain health. Dietary requirements can be met by choline by itself or in the form of choline phospholipids , such as phosphatidylcholine . Choline is not formally classified as a vitamin despite being an essential nutrient with an amino acid –like structure and metabolism. Choline
900-501: Is associated with an increased risk of neural tube defects . Higher maternal intake of choline is likely associated with better neurocognition/neurodevelopment in children. Choline and folate, interacting with vitamin B 12 , act as methyl donors to homocysteine to form methionine, which can then go on to form SAM ( S -adenosylmethionine). SAM is the substrate for almost all methylation reactions in mammals. It has been suggested that disturbed methylation via SAM could be responsible for
960-410: Is catalyzed by a serine decarboxylase . The synthesis of choline from ethanolamine may take place in three parallel pathways, where three consecutive N -methylation steps catalyzed by a methyl transferase are carried out on either the free-base, phospho-bases, or phosphatidyl-bases. The source of the methyl group is S -adenosyl- L -methionine and S -adenosyl- L -homocysteine is generated as
1020-405: Is due to trimethylamine (TMA) formed by the gut microbes from the unabsorbed choline (see trimethylaminuria ). The liver oxidizes TMA to trimethylamine N -oxide (TMAO). Elevated levels of TMA and TMAO in the body have been linked to increased risk of atherosclerosis and mortality. Thus, excessive choline intake has been hypothetized to increase these risks in addition to carnitine , which also
1080-417: Is excreted into urine in humans. Excretion happens via transporters that occur within kidneys (see transport ). Trimethylglycine is demethylated in the liver and kidneys to dimethylglycine ( tetrahydrofolate receives one of the methyl groups). Methylglycine forms, is excreted into urine, or is demethylated to glycine . Choline and its derivatives have many biological functions. Notably choline serves as
1140-702: Is formed into TMA and TMAO by gut bacteria. However, choline intake has not been shown to increase the risk of dying from cardiovascular diseases . It is plausible that elevated TMA and TMAO levels are just a symptom of other underlying illnesses or genetic factors that predispose individuals for increased mortality. Such factors may have not been properly accounted for in certain studies observing TMA and TMAO level related mortality. Causality may be reverse or confounding and large choline intake might not increase mortality in humans. For example, kidney dysfunction predisposes for cardiovascular diseases, but can also decrease TMA and TMAO excretion. Low maternal intake of choline
1200-526: Is highest in organ meats and egg yolks though it is found to a lesser degree in non-organ meats, grains, vegetables, fruit and dairy products . Cooking oils and other food fats have about 5 mg/100 g of total choline. In the United States, food labels express the amount of choline in a serving as a percentage of Daily Value (%DV) based on the Adequate Intake of 550 mg/day. 100% of
1260-421: Is insufficient to meet cellular functions, requiring that some choline be obtained from foods or dietary supplements . Foods rich in choline include meats, poultry, eggs, and other animal-based products, cruciferous vegetables , beans, nuts, and whole grains . Choline is present in breast milk and is commonly added as an ingredient to baby foods . Choline is a quaternary ammonium cation . The cholines are
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#17330853035541320-726: Is made of proteins. Such cell structures include: The mechanisms by which such non-membrane bounded organelles form and retain their spatial integrity have been likened to liquid-liquid phase separation . The second, more restrictive definition of organelle includes only those cell compartments that contain deoxyribonucleic acid (DNA), having originated from formerly autonomous microscopic organisms acquired via endosymbiosis . Using this definition, there would only be two broad classes of organelles (i.e. those that contain their own DNA, and have originated from endosymbiotic bacteria ): Other organelles are also suggested to have endosymbiotic origins, but do not contain their own DNA (notably
1380-481: Is required to produce acetylcholine – a neurotransmitter – and S -adenosylmethionine (SAM), a universal methyl donor. Upon methylation SAM is transformed into S-adenosyl homocysteine . Symptomatic choline deficiency causes non-alcoholic fatty liver disease and muscle damage. Excessive consumption of choline (greater than 7.5 grams per day) can cause low blood pressure , sweating , diarrhea , and fish-like body smell due to trimethylamine , which forms in
1440-441: Is suspected to be due to deficiency of choline derived trimethylglycine, which functions as an osmoregulator. Estrogen production is a relevant factor which predisposes individuals to deficiency along with low dietary choline intake. Estrogens activate phosphatidylcholine producing PEMT enzymes. Women before menopause have lower dietary need for choline than men due to women's higher estrogen production. Without estrogen therapy ,
1500-455: The EU countries . The EFSA has not set any upper limits for intake. Individual EU countries may have more specific recommendations. The National Academy of Medicine (NAM) recommendations apply in the United States, Australia and New Zealand. Twelve surveys undertaken in 9 EU countries between 2000 and 2011 estimated choline intake of adults in these countries to be 269–468 milligrams per day. Intake
1560-427: The endomembrane system (such as the nuclear envelope , endoplasmic reticulum , and Golgi apparatus ), and other structures such as mitochondria and plastids . While prokaryotes do not possess eukaryotic organelles, some do contain protein -shelled bacterial microcompartments , which are thought to act as primitive prokaryotic organelles ; and there is also evidence of other membrane-bounded structures. Also,
1620-431: The intestinal absorption of lipids . Choline is a precursor to acetylcholine , a neurotransmitter that plays a necessary role in muscle contraction , memory and neural development . Nonetheless, there is little acetylcholine in the human body relative to other forms of choline. Neurons also store choline in the form of phospholipids to their cell membranes for the production of acetylcholine. In humans, choline
1680-670: The EU and the US, it is mandatory to add at least 7 mg of choline per 100 kilocalories (kcal) to every infant formula. In the EU, levels above 50 mg/100 kcal are not allowed. Trimethylglycine is a functional metabolite of choline. It substitutes for choline nutritionally, but only partially. High amounts of trimethylglycine occur in wheat bran (1,339 mg/100 g), toasted wheat germ (1,240 mg/100 g) and spinach (600–645 mg/100 g), for example. The following table contains updated sources of choline to reflect
1740-626: The Planctomycetota species Gemmata obscuriglobus , a nucleus-like structure surrounded by lipid membranes has been reported. Compartmentalization is a feature of prokaryotic photosynthetic structures. Purple bacteria have "chromatophores" , which are reaction centers found in invaginations of the cell membrane. Green sulfur bacteria have chlorosomes , which are photosynthetic antenna complexes found bonded to cell membranes. Cyanobacteria have internal thylakoid membranes for light-dependent photosynthesis ; studies have revealed that
1800-495: The blood side of the barrier, but also on the membranes of astrocytes and neurons. OCT1s and OCT2s are not associated with the acetylcholine production. They transport choline with low affinity. OCT1s transport choline primarily in the liver and kidneys; OCT2s in kidneys and the brain. Choline is stored in the cell membranes and organelles as phospholipids, and inside cells as phosphatidylcholines and glycerophosphocholines. Even at choline doses of 2–8 g, little choline
1860-449: The choline intake to be too low in some US subpopulations. Intake was 315.2–318.8 mg/d in 2+ year olds between this time period. Out of 2+ year olds, only 15.6 ± 0.8 % of males and 6.1 ± 0.6 % of females exceeded the adequate intake (AI). AI was exceeded by 62.9 ± 3.1 % of 2- to 3-year-olds, 45.4 ± 1.6 % of 4- to 8-year-olds, 9.0 ± 1.0 % of 9- to 13-year-olds, 1.8 ± 0.4 % of 14–18 and 6.6 ± 0.5 % of 19+ year olds. Upper intake level
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1920-455: The choline needs of post-menopausal women are similar to men's. Some single-nucleotide polymorphisms (genetic factors) affecting choline and folate metabolism are also relevant. Certain gut microbes also degrade choline more efficiently than others, so they are also relevant. In deficiency, availability of phosphatidylcholines in the liver are decreased – these are needed for formation of VLDLs. Thus VLDL-mediated fatty acid transport out of
1980-480: The compound slowly breaks down to ethylene glycol , polyethylene glycols , and TMA. Choline chloride can be made by treating TMA with 2-chloroethanol : Choline has historically been produced from natural sources, such as via hydrolysis of lecithin . Choline is widespread in living beings. In most animals, choline phospholipids are necessary components in cell membranes , in the membranes of cell organelles , and in very low-density lipoproteins . Choline
2040-511: The daily value means that a serving of food has 550 mg of choline. "Total choline" is defined as the sum of free choline and choline-containing phospholipids, without accounting for mass fraction. Human breast milk is rich in choline. Exclusive breastfeeding corresponds to about 120 mg of choline per day for the baby. Increase in a mother's choline intake raises the choline content of breast milk and low intake decreases it. Infant formulas may or may not contain enough choline. In
2100-432: The diet and are able to biosynthesize limited amounts of it via PEMT . Symptomatic deficiency is often caused by certain diseases or by other indirect causes. Severe deficiency causes muscle damage and non-alcoholic fatty liver disease , which may develop into cirrhosis . Besides humans, fatty liver is also a typical sign of choline deficiency in other animals. Bleeding in the kidneys can also occur in some species. This
2160-559: The dietary need for choline. In rodents, 70% of phosphatidylcholines are formed via the PEMT route and only 30% via the CDP-choline route. In knockout mice , PEMT inactivation makes them completely dependent on dietary choline. In humans, choline is absorbed from the intestines via the SLC44A1 (CTL1) membrane protein via facilitated diffusion governed by the choline concentration gradient and
2220-433: The distinction between the two. In the 1830s, Félix Dujardin refuted Ehrenberg theory which said that microorganisms have the same organs of multicellular animals, only minor. Credited as the first to use a diminutive of organ (i.e., little organ) for cellular structures was German zoologist Karl August Möbius (1884), who used the term organula (plural of organulum , the diminutive of Latin organum ). In
2280-513: The electrical potential across the enterocyte membranes. SLC44A1 has limited ability to transport choline: at high concentrations part of it is left unabsorbed. Absorbed choline leaves the enterocytes via the portal vein , passes the liver and enters systemic circulation . Gut microbes degrade the unabsorbed choline to trimethylamine, which is oxidized in the liver to trimethylamine N -oxide . Phosphocholine and glycerophosphocholines are hydrolyzed via phospholipases to choline, which enters
2340-937: The ethanolamine group of the phosphatidylethanolamine to form choline in the form of a phosphatidylcholine. Three S -adenosylhomocysteines (SAHs) are formed as a byproduct. Choline can also be released from more complex precursors. For example, phosphatidylcholines (PC) can be hydrolyzed to choline (Chol) in most cell types. Choline can also be produced by the CDP-choline route, cytosolic choline kinases (CK) phosphorylate choline with ATP to phosphocholine (PChol). This happens in some cell types like liver and kidney. Choline-phosphate cytidylyltransferases (CPCT) transform PChol to CDP-choline (CDP-Chol) with cytidine triphosphate (CTP). CDP-choline and diglyceride are transformed to PC by diacylglycerol cholinephosphotransferase (CPT). In humans, certain PEMT-enzyme mutations and estrogen deficiency (often due to menopause ) increase
2400-421: The flagellum – see evolution of flagella ). Eukaryotic cells are structurally complex, and by definition are organized, in part, by interior compartments that are themselves enclosed by lipid membranes that resemble the outermost cell membrane . The larger organelles, such as the nucleus and vacuoles , are easily visible with the light microscope . They were among the first biological discoveries made after
2460-451: The gastrointestinal tract, which has implications for cardiovascular health. In one study, risk of stroke over a ten-year period was increased by about 40% in users of alpha-GPC. Choline Choline is a cation with the chemical formula [(CH 3 ) 3 NCH 2 CH 2 OH] . Choline forms various salts , such as choline chloride and choline bitartrate . It is an essential nutrient for humans and many other animals, and
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2520-456: The invention of the microscope . Not all eukaryotic cells have each of the organelles listed below. Exceptional organisms have cells that do not include some organelles (such as mitochondria) that might otherwise be considered universal to eukaryotes. 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
2580-706: The liver decreases leading to fat accumulation in the liver. Other simultaneously occurring mechanisms explaining the observed liver damage have also been suggested. For example, choline phospholipids are also needed in mitochondrial membranes. Their unavailability leads to the inability of mitochondrial membranes to maintain proper electrochemical gradient , which, among other things, is needed for degrading fatty acids via β-oxidation . Fat metabolism within liver therefore decreases. Excessive doses of choline can have adverse effects. Daily 8–20 g doses of choline, for example, have been found to cause low blood pressure , nausea , diarrhea and fish-like body odor . The odor
2640-429: The membranes of most cell organelles. Phosphatidylcholines are structurally important part of the cell membranes. In humans, 40–50% of their phospholipids are phosphatidylcholines. Choline phospholipids also form lipid rafts in the cell membranes along with cholesterol . The rafts are centers, for example for cholinergic receptors and receptor signal transduction enzymes. Phosphatidylcholines are needed for
2700-466: The metabolism of choline. Rich dietary sources of choline and choline phospholipids include organ meats , egg yolks , dairy products , peanuts , certain beans , nuts and seeds . Vegetables with pasta and rice also contribute to choline intake in the American diet . In plants, the first step in de novo biosynthesis of choline is the decarboxylation of serine into ethanolamine , which
2760-413: The mitochondria in the tongue, kidneys, muscles and heart. They are associated with the mitochondrial oxidation of choline to trimethylglycine. CTL1s and CTL2s are not associated with the acetylcholine production, but transport choline together via the blood–brain barrier . Only CTL2s occur on the brain side of the barrier. They also remove excess choline from the neurons back to blood. CTL1s occur only on
2820-408: The new Daily Value and the new Nutrition Facts and Supplement Facts Labels. It reflects data from the U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019. DV = Daily Value. The U.S. Food and Drug Administration (FDA) developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet. The DV for choline
2880-562: The nutrient content of many foods and provides a comprehensive list of foods containing choline arranged by nutrient content. Insufficient data is available to establish an estimated average requirement (EAR) for choline, so the Food and Nutrition Board established adequate intakes (AIs). For adults, the AI for choline was set at 550 mg/day for men and 425 mg/day for women. These values have been shown to prevent hepatic alteration in men. However,
2940-523: The portal vein. Due to their water solubility, some of them escape unchanged to the portal vein. Fat-soluble choline-containing compounds (phosphatidylcholines and sphingomyelins ) are either hydrolyzed by phospholipases or enter the lymph incorporated into chylomicrons . In humans, choline is transported as a free ion in blood. Choline–containing phospholipids and other substances, like glycerophosphocholines, are transported in blood lipoproteins . Blood plasma choline levels in healthy fasting adults
3000-405: The prokaryotic flagellum which protrudes outside the cell, and its motor, as well as the largely extracellular pilus , are often spoken of as organelles. In biology, organs are defined as confined functional units within an organism . The analogy of bodily organs to microscopic cellular substructures is obvious, as from even early works, authors of respective textbooks rarely elaborate on
3060-430: The pulmonary and other muscles in humans via acetylcholine deficiency. In knockout mice , their dysfunction results easily in death with cyanosis and paralysis . CTL1s have moderate affinity for choline and transport it in almost all tissues, including the intestines, liver, kidneys, placenta and mitochondria . CTL1s supply choline for phosphatidylcholine and trimethylglycine production. CTL2s occur especially in
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#17330853035543120-465: The relation between folate and NTDs. This may also apply to choline. Certain mutations that disturb choline metabolism increase the prevalence of NTDs in newborns, but the role of dietary choline deficiency remains unclear, as of 2015. Organelle Organelles are identified by microscopy , and can also be purified by cell fractionation . There are many types of organelles, particularly in eukaryotic cells . They include structures that make up
3180-458: The study used to derive these values did not evaluate whether less choline would be effective, as researchers only compared a choline-free diet to a diet containing 550 mg of choline per day. From this, the AIs for children and adolescents were extrapolated. Recommendations are in milligrams per day (mg/day). The European Food Safety Authority (EFSA) recommendations are general recommendations for
3240-591: The synthesis of VLDLs : 70–95% of their phospholipids are phosphatidylcholines in humans. Choline is also needed for the synthesis of pulmonary surfactant , which is a mixture consisting mostly of phosphatidylcholines. The surfactant is responsible for lung elasticity, that is for lung tissue's ability to contract and expand. For example, deficiency of phosphatidylcholines in the lung tissues has been linked to acute respiratory distress syndrome . Phosphatidylcholines are excreted into bile and work together with bile acid salts as surfactants in it, thus helping with
3300-658: The tables below (e.g., some that are listed as double-membrane are sometimes found with single or triple membranes). In addition, the number of individual organelles of each type found in a given cell varies depending upon the function of that cell. The cell membrane and cell wall are not organelles. ( mRNP complexes) Other related structures: Prokaryotes are not as structurally complex as eukaryotes, and were once thought to have little internal organization, and lack cellular compartments and internal membranes ; but slowly, details are emerging about prokaryotic internal structures that overturn these assumptions. An early false turn
3360-438: The term to include only those cell compartments that contain deoxyribonucleic acid (DNA), having originated from formerly autonomous microscopic organisms acquired via endosymbiosis . The first, broader conception of organelles is that they are membrane-bounded structures. However, even by using this definition, some parts of the cell that have been shown to be distinct functional units do not qualify as organelles. Therefore,
3420-514: The use of organelle to also refer to non-membrane bounded structures such as ribosomes is common and accepted. This has led many texts to delineate between membrane-bounded and non-membrane bounded organelles. The non-membrane bounded organelles, also called large biomolecular complexes , are large assemblies of macromolecules that carry out particular and specialized functions, but they lack membrane boundaries. Many of these are referred to as "proteinaceous organelles" as their main structure
3480-480: Was 269–444 mg/day in adult women and 332–468 mg/day in adult men. Intake was 75–127 mg/day in infants, 151–210 mg/day in 1- to 3-year-olds, 177–304 mg/day in 3- to 10-year-olds and 244–373 mg/day in 10- to 18-year-olds. The total choline intake mean estimate was 336 mg/day in pregnant adolescents and 356 mg/day in pregnant women. A study based on the NHANES 2009–2012 survey estimated
3540-403: Was not exceeded in any subpopulations. A 2013–2014 NHANES study of the US population found the choline intake of 2- to 19-year-olds to be 256 ± 3.8 mg/day and 339 ± 3.9 mg/day in adults 20 and over. Intake was 402 ± 6.1 mg/d in men 20 and over and 278 mg/d in women 20 and over. Symptomatic choline deficiency is rare in humans. Most obtain sufficient amounts of it from
3600-516: Was the idea developed in the 1970s that bacteria might contain cell membrane folds termed mesosomes , but these were later shown to be artifacts produced by the chemicals used to prepare the cells for electron microscopy . However, there is increasing evidence of compartmentalization in at least some prokaryotes. Recent research has revealed that at least some prokaryotes have microcompartments , such as carboxysomes . These subcellular compartments are 100–200 nm in diameter and are enclosed by
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