Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole ) fused together. It is water -soluble. Purine also gives its name to the wider class of molecules , purines , which include substituted purines and their tautomers . They are the most widely occurring nitrogen -containing heterocycles in nature.
104-590: Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney . In general, plant-based diets are low in purines. High-purine plants and algae include some legumes ( lentils , soybeans , and black-eyed peas ) and spirulina . Examples of high-purine sources include: sweetbreads , anchovies , sardines , liver, beef kidneys, brains , meat extracts (e.g., Oxo , Bovril ), herring , mackerel , scallops , game meats , yeast ( beer , yeast extract , nutritional yeast ) and gravy . A moderate amount of purine
208-426: A 2.39). If dissolved in pure water, the pH is halfway between these two pKa values. Purine is aromatic , having four tautomers each with a hydrogen bonded to a different one of the four nitrogen atoms. These are identified as 1-H, 3-H, 7-H, and 9-H (see image of numbered ring). The common crystalline form favours the 7-H tautomer, while in polar solvents both the 9-H and 7-H tautomers predominate. Substituents to
312-426: A benign tumour the most common type of liver tumour, thought to be congenital. A genetic disorder causing multiple cysts to form in the liver tissue, usually in later life, and usually asymptomatic, is polycystic liver disease . Diseases that interfere with liver function will lead to derangement of these processes. However, the liver has a great capacity to regenerate and has a large reserve capacity. In most cases,
416-407: A Dicer enzyme from an RNA sequence that is from a regulator gene. These short strands bind to a RISC complex . They match up with sequences in the upstream region of a transcribed gene due to their complementarity to act as a silencer for the gene in three ways. One is by preventing a ribosome from binding and initiating translation. Two is by degrading the mRNA that the complex has bound to. And three
520-426: A coding region or a transcribed gene, and results in base pairing. These short nucleic acid sequences are commonly found in nature and have regulatory functions such as gene silencing. Antisense transcripts are stretches of non coding mRNA that are complementary to the coding sequence. Genome wide studies have shown that RNA antisense transcripts occur commonly within nature. They are generally believed to increase
624-446: A double-strand like structure. Depending on how close together the parts of the sequence are that are self-complementary, the strand may form hairpin loops, junctions, bulges or internal loops. RNA is more likely to form these kinds of structures due to base pair binding not seen in DNA, such as guanine binding with uracil. Complementarity can be found between short nucleic acid stretches and
728-410: A dual blood supply from the hepatic portal vein and hepatic arteries. The hepatic portal vein delivers around 75% of the liver's blood supply and carries venous blood drained from the spleen, gastrointestinal tract, and its associated organs. The hepatic arteries supply arterial blood to the liver, accounting for the remaining quarter of its blood flow. Oxygen is provided from both sources; about half of
832-408: A key role in this phenomenon. At birth, the liver comprises roughly 4% of body weight and weighs on average about 120 g (4 oz). Over the course of further development, it will increase to 1.4–1.6 kg (3.1–3.5 lb) but will only take up 2.5–3.5% of body weight. Hepatosomatic index (HSI) is the ratio of liver weight to body weight. In the growing fetus, a major source of blood to
936-410: A population of the bipotential hepatoblasts. Hepatic stellate cells are derived from mesenchyme. After migration of hepatoblasts into the septum transversum mesenchyme, the hepatic architecture begins to be established, with liver sinusoids and bile canaliculi appearing. The liver bud separates into the lobes. The left umbilical vein becomes the ductus venosus and the right vitelline vein becomes
1040-409: A protective benefit against liver cancer for moderate coffee drinkers. A 2017 study revealed that the positive effects of caffeine on the liver were evident regardless of the coffee preparation method. Complementarity (molecular biology) In molecular biology , complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity
1144-409: A role in the production of clotting factors, as well as red blood cell production. Some of the proteins synthesized by the liver include coagulation factors I (fibrinogen), II (prothrombin), V , VII , VIII , IX , X , XI , XII , XIII , as well as protein C , protein S and antithrombin . The liver is a major site of production for thrombopoietin , a glycoprotein hormone that regulates
SECTION 10
#17331041925491248-500: A suitable ( ambigraphic ) nucleic acid notation for complementary bases (i.e. guanine = b , cytosine = q , adenine = n , and thymine = u ), which makes it is possible to complement entire DNA sequences by simply rotating the text "upside down". For instance, with the previous alphabet, buqn (GTCA) would read as ubnq (TGAC, reverse complement) if turned upside down. Ambigraphic notations readily visualize complementary nucleic acid stretches such as palindromic sequences. This feature
1352-420: A superficial division of the liver into a left and right lobe. From below, the two additional lobes are located between the right and left lobes, one in front of the other. A line can be imagined running from the left of the vena cava and all the way forward to divide the liver and gallbladder into two halves. This line is called Cantlie's line . Other anatomical landmarks include the ligamentum venosum and
1456-476: A twisted DNA double helix formation without any spatial distortions. Hydrogen bonding between the nucleobases also stabilizes the DNA double helix. Complementarity of DNA strands in a double helix make it possible to use one strand as a template to construct the other. This principle plays an important role in DNA replication , setting the foundation of heredity by explaining how genetic information can be passed down to
1560-657: Is uracil instead of thymine. Other notable purines are hypoxanthine , xanthine , theophylline , theobromine , caffeine , uric acid and isoguanine . Aside from the crucial roles of purines (adenine and guanine) in DNA and RNA, purines are also significant components in a number of other important biomolecules, such as ATP , GTP , cyclic AMP , NADH , and coenzyme A . Purine ( 1 ) itself, has not been found in nature, but it can be produced by organic synthesis . They may also function directly as neurotransmitters , acting upon purinergic receptors . Adenosine activates adenosine receptors . The word purine ( pure urine )
1664-401: Is a "satellite" of hepatitis B virus (it can only infect in the presence of hepatitis B), and co-infects nearly 20 million people with hepatitis B, globally. Hepatic encephalopathy is caused by an accumulation of toxins in the bloodstream that are normally removed by the liver. This condition can result in coma and can prove fatal. Budd–Chiari syndrome is a condition caused by blockage of
1768-415: Is a dark reddish brown, wedge-shaped organ with two lobes of unequal size and shape. A human liver normally weighs approximately 1.5 kilograms (3.3 pounds) and has a width of about 15 centimetres (6 inches). There is considerable size variation between individuals, with the standard reference range for men being 970–1,860 grams (2.14–4.10 lb) and for women 600–1,770 g (1.32–3.90 lb). It
1872-635: Is achieved by distinct interactions between nucleobases : adenine , thymine ( uracil in RNA ), guanine and cytosine . Adenine and guanine are purines , while thymine, cytosine and uracil are pyrimidines . Purines are larger than pyrimidines. Both types of molecules complement each other and can only base pair with the opposing type of nucleobase. In nucleic acid, nucleobases are held together by hydrogen bonding , which only works efficiently between adenine and thymine and between guanine and cytosine. The base complement A = T shares two hydrogen bonds, while
1976-735: Is also contained in red meat, beef , pork , poultry , fish and seafood , asparagus , cauliflower , spinach , mushrooms , green peas , lentils , dried peas, beans , oatmeal , wheat bran , wheat germ , and haws . Purines and pyrimidines make up the two groups of nitrogenous bases , including the two groups of nucleotide bases . The purine bases are guanine (G) and adenine (A) which form corresponding nucleosides- deoxyribonucleosides ( deoxyguanosine and deoxyadenosine ) with deoxyribose moiety and ribonucleosides ( guanosine , adenosine ) with ribose moiety. These nucleosides with phosphoric acid form corresponding nucleotides (deoxyguanylate, deoxyadenylate and guanylate, adenylate) which are
2080-503: Is associated with a decreased risk. Moderate intake of purine-rich vegetables or protein is not associated with an increased risk of gout. Similar results have been found with the risk of hyperuricemia . In addition to in vivo synthesis of purines in purine metabolism , purine can also be synthesized artificially. Purine is obtained in good yield when formamide is heated in an open vessel at 170 °C for 28 hours. This remarkable reaction and others like it have been discussed in
2184-407: Is both the heaviest internal organ and the largest gland in the human body. It is located in the right upper quadrant of the abdominal cavity , resting just below the diaphragm, to the right of the stomach, and overlying the gallbladder . The liver is connected to two large blood vessels : the hepatic artery and the portal vein . The hepatic artery carries oxygen-rich blood from the aorta via
SECTION 20
#17331041925492288-476: Is by providing a new double-stranded RNA (dsRNA) sequence that Dicer can act upon to create more miRNA to find and degrade more copies of the gene. Small interfering RNAs (siRNAs) are similar in function to miRNAs; they come from other sources of RNA, but serve a similar purpose to miRNAs. Given their short length, the rules for complementarity means that they can still be very discriminating in their targets of choice. Given that there are four choices for each base in
2392-450: Is known as the duodenal impression. The inferior surface of the left lobe of the liver presents behind and to the left of the gastric impression. This is moulded over the upper front surface of the stomach, and to the right of this is a rounded eminence, the tuber omentale , which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of the lesser omentum . Microscopically, each liver lobe
2496-449: Is responsible for the breakdown and excretion of many waste products. It plays a key role in breaking down or modifying toxic substances (e.g., methylation ) and most medicinal products in a process called drug metabolism . This sometimes results in toxication , when the metabolite is more toxic than its precursor. Preferably, the toxins are conjugated to avail excretion in bile or urine. The liver converts ammonia into urea as part of
2600-405: Is seen to be made up of hepatic lobules . The lobules are roughly hexagonal, and consist of plates of hepatocytes , and sinusoids radiating from a central vein towards an imaginary perimeter of interlobular portal triads. The central vein joins to the hepatic vein to carry blood out from the liver. A distinctive component of a lobule is the portal triad , which can be found running along each of
2704-466: Is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences , such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary , much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to
2808-405: Is the tube of endoderm that extends out from the foregut into the surrounding mesenchyme. The mesenchyme of septum transversum induces this endoderm to proliferate, to branch, and to form the glandular epithelium of the liver. A portion of the hepatic diverticulum (that region closest to the digestive tube) continues to function as the drainage duct of the liver, and a branch from this duct produces
2912-413: Is uneven and concave. It is covered in peritoneum apart from where it attaches the gallbladder and the porta hepatis. The fossa of gallbladder lies to the right of the quadrate lobe, occupied by the gallbladder with its cystic duct close to the right end of porta hepatis. Several impressions on the surface of the liver accommodate the various adjacent structures and organs. Underneath the right lobe and to
3016-441: The ampulla of Vater . The liver plays a major role in carbohydrate, protein, amino acid, and lipid metabolism. The liver performs several roles in carbohydrate metabolism. The liver is responsible for the mainstay of protein metabolism , synthesis as well as degradation. All plasma proteins except Gamma-globulins are synthesised in the liver. It is also responsible for a large part of amino acid synthesis . The liver plays
3120-425: The celiac trunk , whereas the portal vein carries blood rich in digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas . These blood vessels subdivide into small capillaries known as liver sinusoids , which then lead to hepatic lobules . Hepatic lobules are the functional units of the liver. Each lobule is made up of millions of hepatic cells (hepatocytes), which are
3224-442: The duodenum to help with digestion . The liver's highly specialized tissue , consisting mostly of hepatocytes , regulates a wide variety of high-volume biochemical reactions, including the synthesis and breakdown of small and complex organic molecules, many of which are necessary for normal vital functions. Estimates regarding the organ's total number of functions vary, but is generally cited as being around 500. For this reason,
Purine - Misplaced Pages Continue
3328-400: The enzymes required for more purine formation. This self-inhibition occurs as they also activate the enzymes needed for pyrimidine formation. Pyrimidine simultaneously self-inhibits and activates purine in a similar manner. Because of this, there is nearly an equal amount of both substances in the cell at all times. Purine is both a very weak acid ( pK a 8.93) and an even weaker base ( pK
3432-421: The fibrinogen beta chain protein. Organogenesis , the development of the organs, takes place from the third to the eighth week during embryogenesis . The origins of the liver lie in both the ventral portion of the foregut endoderm (endoderm being one of the three embryonic germ layers ) and the constituents of the adjacent septum transversum mesenchyme . In the human embryo , the hepatic diverticulum
3536-399: The hepatic veins (including thrombosis ) that drain the liver. It presents with the classical triad of abdominal pain, ascites and liver enlargement . Many diseases of the liver are accompanied by jaundice caused by increased levels of bilirubin in the system. The bilirubin results from the breakup of the hemoglobin of dead red blood cells; normally, the liver removes bilirubin from
3640-428: The ornithine cycle or the urea cycle, and the urea is excreted in the urine. Because the liver is an expandable organ, large quantities of blood can be stored in its blood vessels. Its normal blood volume, including both that in the hepatic veins and that in the hepatic sinuses, is about 450 milliliters, or almost 10 percent of the body's total blood volume. When high pressure in the right atrium causes backpressure in
3744-474: The polymerase chain reaction , PCR. Two strands of complementary sequence are referred to as sense and anti-sense . The sense strand is, generally, the transcribed sequence of DNA or the RNA that was generated in transcription, while the anti-sense strand is the strand that is complementary to the sense sequence. Self-complementarity refers to the fact that a sequence of DNA or RNA may fold back on itself, creating
3848-403: The right and left triangular ligaments . These peritoneal ligaments are not related to the anatomic ligaments in joints, and the right and left triangular ligaments have no known functional importance, though they serve as surface landmarks. The falciform ligament functions to attach the liver to the posterior portion of the anterior body wall. The visceral surface or inferior surface
3952-410: The round ligament of the liver , which further divide the left side of the liver in two sections. An important anatomical landmark, the porta hepatis , divides this left portion into four segments, which can be numbered starting at the caudate lobe as I in an anticlockwise manner. From this parietal view, seven segments can be seen, because the eighth segment is only visible in the visceral view. On
4056-452: The 5 hours have passed and the formamide-phosphorus oxychloride-adenine solution cools down, water is put into the flask containing the formamide and now-formed adenine. The water-formamide-adenine solution is then poured through a filtering column of activated charcoal. The water and formamide molecules, being small molecules, will pass through the charcoal and into the waste flask; the large adenine molecules, however, will attach or “adsorb” to
4160-504: The absorption of vitamin K from the diet. Some of the bile drains directly into the duodenum, and some is stored in the gallbladder. The liver produces insulin-like growth factor 1 , a polypeptide protein hormone that plays an important role in childhood growth and continues to have anabolic effects in adults. The liver is responsible for the breakdown of insulin and other hormones . The liver breaks down bilirubin via glucuronidation , facilitating its excretion into bile. The liver
4264-555: The active NTP and dNTP pools. Deamination of purine bases can result in accumulation of such nucleotides as ITP , dITP , XTP and dXTP . Defects in enzymes that control purine production and breakdown can severely alter a cell's DNA sequences, which may explain why people who carry certain genetic variants of purine metabolic enzymes have a higher risk for some types of cancer . Organisms in all three domains of life, eukaryotes , bacteria and archaea , are able to carry out de novo biosynthesis of purines . This ability reflects
Purine - Misplaced Pages Continue
4368-658: The adenine into the ammonia-water solution. The solution containing water, ammonia, and adenine is then left to air dry, with the adenine losing solubility due to the loss of ammonia gas that previously made the solution basic and capable of dissolving adenine, thus causing it to crystallize into a pure white powder that can be stored. Oro and Kamat (1961) and Orgel co-workers (1966, 1967) have shown that four molecules of HCN tetramerize to form diaminomaleodinitrile ( 12 ), which can be converted into almost all naturally occurring purines. For example, five molecules of HCN condense in an exothermic reaction to make adenine , especially in
4472-425: The antisense transcript acts as a stabilizer to the sense script. miRNAs , microRNA, are short RNA sequences that are complementary to regions of a transcribed gene and have regulatory functions. Current research indicates that circulating miRNA may be utilized as novel biomarkers, hence show promising evidence to be utilized in disease diagnostics. MiRNAs are formed from longer sequences of RNA that are cut free by
4576-481: The archaeal species unable to synthesize purines are able to acquire exogenous purines for growth., and are thus analogous to purine mutants of eukaryotes, e.g. purine mutants of the Ascomycete fungus Neurospora crassa , that also require exogenous purines for growth. Higher levels of meat and seafood consumption are associated with an increased risk of gout , whereas a higher level of consumption of dairy products
4680-423: The base pair G ≡ C has three hydrogen bonds. All other configurations between nucleobases would hinder double helix formation. DNA strands are oriented in opposite directions, they are said to be antiparallel . A complementary strand of DNA or RNA may be constructed based on nucleobase complementarity. Each base pair, A = T vs. G ≡ C, takes up roughly the same space, thereby enabling
4784-403: The basic metabolic cells. The lobules are held together by a fine, dense, irregular, fibroelastic connective tissue layer extending from the fibrous capsule covering the entire liver known as Glisson's capsule after British doctor Francis Glisson . This tissue extends into the structure of the liver by accompanying the blood vessels, ducts, and nerves at the hepatic hilum. The whole surface of
4888-455: The blood and constitute plasma proteins and hepatokines . Other liver-specific proteins are certain liver enzymes such as HAO1 and RDH16 , proteins involved in bile synthesis such as BAAT and SLC27A5 , and transporter proteins involved in the metabolism of drugs, such as ABCB11 and SLC2A2 . Examples of highly liver-specific proteins include apolipoprotein A II , coagulation factors F2 and F9 , complement factor related proteins , and
4992-520: The blood and excretes it through bile. Other disorders caused by excessive alcohol consumption are grouped under alcoholic liver diseases and these include alcoholic hepatitis , fatty liver , and cirrhosis . Factors contributing to the development of alcoholic liver diseases are not only the quantity and frequency of alcohol consumption, but can also include gender, genetics, and liver insult. Liver damage can also be caused by drugs , particularly paracetamol and drugs used to treat cancer. A rupture of
5096-474: The building blocks of DNA and RNA , respectively. Purine bases also play an essential role in many metabolic and signalling processes within the compounds guanosine monophosphate (GMP) and adenosine monophosphate (AMP). In order to perform these essential cellular processes, both purines and pyrimidines are needed by the cell , and in similar quantities. Both purine and pyrimidine are self- inhibiting and activating . When purines are formed, they inhibit
5200-467: The centre of each segment are branches of the portal vein, hepatic artery, and bile duct. In the periphery of each segment is vascular outflow through the hepatic veins. The classification system uses the vascular supply in the liver to separate the functional units (numbered I to VIII) with unit 1, the caudate lobe, receiving its supply from both the right and the left branches of the portal vein. It contains one or more hepatic veins which drain directly into
5304-445: The charcoal due to the van der waals forces that interact between the adenine and the carbon in the charcoal. Because charcoal has a large surface area, it's able to capture the majority of molecules that pass a certain size (greater than water and formamide) through it. To extract the adenine from the charcoal-adsorbed adenine, ammonia gas dissolved in water (aqua ammonia) is poured onto the activated charcoal-adenine structure to liberate
SECTION 50
#17331041925495408-580: The coding potential of the genetic code and add an overall layer of complexity to gene regulation. So far, it is known that 40% of the human genome is transcribed in both directions, underlining the potential significance of reverse transcription. It has been suggested that complementary regions between sense and antisense transcripts would allow generation of double stranded RNA hybrids, which may play an important role in gene regulation. For example, hypoxia-induced factor 1α mRNA and β-secretase mRNA are transcribed bidirectionally, and it has been shown that
5512-414: The common hepatic duct to form the common bile duct. The biliary system and connective tissue is supplied by the hepatic artery alone. Bile either drains directly into the duodenum via the common bile duct, or is temporarily stored in the gallbladder via the cystic duct. The common bile duct and the pancreatic duct enter the second part of the duodenum together at the hepatopancreatic ampulla, also known as
5616-416: The complementary bases of the two strands form up and begin to unwind the hairpins until a double-stranded RNA (dsRNA) complex is formed or the complex unwinds back to two separate strands due to mismatches in the hairpins. The secondary structure of the hairpin prior to kissing allows for a stable structure with a relatively fixed change in energy. The purpose of these structures is a balancing of stability of
5720-493: The context of the origin of life . Patented August 20, 1968, the current recognized method of industrial-scale production of adenine is a modified form of the formamide method. This method heats up formamide under 120 °C conditions within a sealed flask for 5 hours to form adenine. The reaction is heavily increased in quantity by using a phosphorus oxychloride (phosphoryl chloride) or phosphorus pentachloride as an acid catalyst and sunlight or ultraviolet conditions. After
5824-421: The damaged section and its replacement by using complementarity to copy information from the other strand, as occurs in the processes of mismatch repair , nucleotide excision repair and base excision repair . Nucleic acids strands may also form hybrids in which single stranded DNA may readily anneal with complementary DNA or RNA. This principle is the basis of commonly performed laboratory techniques such as
5928-406: The decomposition of red blood cells . The liver is also an accessory digestive organ that produces bile , an alkaline fluid containing cholesterol and bile acids , which emulsifies and aids the breakdown of dietary fat . The gallbladder , a small hollow pouch that sits just under the right lobe of liver, stores and concentrates the bile produced by the liver, which is later excreted to
6032-401: The diaphragmatic surface, apart from a triangular bare area where it connects to the diaphragm, the liver is covered by a thin, double-layered membrane, the peritoneum , that helps to reduce friction against other organs. This surface covers the convex shape of the two lobes where it accommodates the shape of the diaphragm. The peritoneum folds back on itself to form the falciform ligament and
6136-464: The direct condensation of purine and pyrimidine nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing purine ribonucleosides was presented by Becker et al . in 2016. Liver The liver is a major metabolic organ exclusively found in vertebrate animals , which performs many essential biological functions such as detoxification of
6240-418: The edge of the liver lobule, where they merge to form bile ducts. Within the liver, these ducts are termed intrahepatic bile ducts, and once they exit the liver, they are considered extrahepatic. The intrahepatic ducts eventually drain into the right and left hepatic ducts, which exit the liver at the transverse fissure , and merge to form the common hepatic duct. The cystic duct from the gallbladder joins with
6344-454: The essentiality of purines for life. The biochemical pathway of synthesis is very similar in eukaryotes and bacterial species, but is more variable among archaeal species. A nearly complete, or complete, set of genes required for purine biosynthesis was determined to be present in 58 of the 65 archaeal species studied. However, also identified were seven archaeal species with entirely, or nearly entirely, absent purine encoding genes. Apparently
SECTION 60
#17331041925496448-564: The family Herpesviridae such as the herpes simplex virus . Chronic (rather than acute) infection with hepatitis B virus or hepatitis C virus is the main cause of liver cancer . Globally, about 248 million individuals are chronically infected with hepatitis B (with 843,724 in the U.S.), and 142 million are chronically infected with hepatitis C (with 2.7 million in the U.S.). Globally there are about 114 million and 20 million cases of hepatitis A and hepatitis E respectively, but these generally resolve and do not become chronic. Hepatitis D virus
6552-448: The functional lobes are further divided into a total of eight subsegments based on a transverse plane through the bifurcation of the main portal vein. The caudate lobe is a separate structure that receives blood flow from both the right- and left-sided vascular branches. The Couinaud classification divides the liver into eight functionally independent liver segments. Each segment has its own vascular inflow, outflow and biliary drainage. In
6656-485: The functions of a mature hepatocyte, and eventually mature hepatocytes appear as highly polarized epithelial cells with abundant glycogen accumulation. In the adult liver, hepatocytes are not equivalent, with position along the portocentrovenular axis within a liver lobule dictating expression of metabolic genes involved in drug metabolism, carbohydrate metabolism , ammonia detoxification, and bile production and secretion. WNT/β-catenin has now been identified to be playing
6760-412: The gallbladder. Besides signals from the septum transversum mesenchyme, fibroblast growth factor from the developing heart also contributes to hepatic competence, along with retinoic acid emanating from the lateral plate mesoderm . The hepatic endodermal cells undergo a morphological transition from columnar to pseudostratified resulting in thickening into the early liver bud . Their expansion forms
6864-412: The hairpin loop vs binding strength with a complementary strand. Too strong an initial binding to a bad location and the strands will not unwind quickly enough; too weak an initial binding and the strands will never fully form the desired complex. These hairpin structures allow for the exposure of enough bases to provide a strong enough check on the initial binding and a weak enough internal binding to allow
6968-405: The imaginary plane, Cantlie's line, joining the gallbladder fossa to the inferior vena cava . The plane separates the liver into the true right and left lobes. The middle hepatic vein also demarcates the true right and left lobes. The right lobe is further divided into an anterior and posterior segment by the right hepatic vein. The left lobe is divided into the medial and lateral segments by
7072-437: The inferior vena cava, allowing placental blood to bypass the liver. In the fetus, the liver does not perform the normal digestive processes and filtration of the infant liver because nutrients are received directly from the mother via the placenta . The fetal liver releases some blood stem cells that migrate to the fetal thymus , creating the T cells (or T lymphocytes). After birth, the formation of blood stem cells shifts to
7176-463: The inferior vena cava. The remainder of the units (II to VIII) are numbered in a clockwise fashion: About 20,000 protein coding genes are expressed in human cells and 60% of these genes are expressed in a normal, adult liver. Over 400 genes are more specifically expressed in the liver, with some 150 genes highly specific for liver tissue. A large fraction of the corresponding liver-specific proteins are mainly expressed in hepatocytes and secreted into
7280-461: The information stored in the sequences. The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology,
7384-423: The left hepatic vein. The hilum of the liver is described in terms of three plates that contain the bile ducts and blood vessels. The contents of the whole plate system are surrounded by a sheath. The three plates are the hilar plate , the cystic plate and the umbilical plate and the plate system is the site of the many anatomical variations to be found in the liver. In the widely used Couinaud system,
7488-445: The liver and drain into the inferior vena cava. The biliary tract is derived from the branches of the bile ducts. The biliary tract, also known as the biliary tree, is the path by which bile is secreted by the liver then transported to the first part of the small intestine, the duodenum . The bile produced in the liver is collected in bile canaliculi , small grooves between the faces of adjacent hepatocytes. The canaliculi radiate to
7592-492: The liver are carried out by the liver cells or hepatocytes. The liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs. Currently, no artificial organ or device is capable of reproducing all the functions of the liver. Some functions can be carried out by liver dialysis , an experimental treatment for liver failure . The liver also accounts for about 20% of resting total body oxygen consumption. The liver receives
7696-417: The liver can be caused by a liver shot used in combat sports. Primary biliary cholangitis is an autoimmune disease of the liver. It is marked by slow progressive destruction of the small bile ducts of the liver, with the intralobular ducts ( Canals of Hering ) affected early in the disease. When these ducts are damaged, bile and other toxins build up in the liver ( cholestasis ) and over time damages
7800-435: The liver has sometimes been described as the body's chemical factory . It is not known how to compensate for the absence of liver function in the long term, although liver dialysis techniques can be used in the short term. Artificial livers have not been developed to promote long-term replacement in the absence of the liver. As of 2018 , liver transplantation is the only option for complete liver failure . The liver
7904-490: The liver in response to injury or inflammation. The most common chronic liver disease is nonalcoholic fatty liver disease , which affects an estimated one-third of the world population. Hepatitis is a common condition of inflammation of the liver. The most usual cause of this is viral , and the most common of these infections are hepatitis A , B , C , D , and E . Some of these infections are sexually transmitted . Inflammation can also be caused by other viruses in
8008-404: The liver is the umbilical vein, which supplies nutrients to the growing fetus. The umbilical vein enters the abdomen at the umbilicus and passes upward along the free margin of the falciform ligament of the liver to the inferior surface of the liver. There, it joins with the left branch of the portal vein. The ductus venosus carries blood from the left portal vein to the left hepatic vein and then to
8112-419: The liver only produces symptoms after extensive damage. Hepatomegaly refers to an enlarged liver and can be due to many causes. It can be palpated in a liver span measurement. Consuming caffeine regularly may help safeguard individuals from liver cirrhosis . Additionally, it has been shown to slow the advancement of liver disease in those already affected, lower the risk of liver fibrosis, and provide
8216-584: The liver tissue in combination with ongoing immune related damage. This can lead to scarring ( fibrosis ) and cirrhosis . Cirrhosis increases the resistance to blood flow in the liver, and can result in portal hypertension . Congested anastomoses between the portal venous system and the systemic circulation, can be a subsequent condition. There are also many pediatric liver diseases, including biliary atresia , alpha-1 antitrypsin deficiency , alagille syndrome , progressive familial intrahepatic cholestasis , Langerhans cell histiocytosis and hepatic hemangioma
8320-467: The liver volume is occupied by parenchymal hepatocytes. Nonparenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. The liver sinusoids are lined with two types of cell, sinusoidal endothelial cells , and phagocytic Kupffer cells . Hepatic stellate cells are nonparenchymal cells found in the perisinusoidal space , between a sinusoid and a hepatocyte. Additionally, intrahepatic lymphocytes are often present in
8424-444: The liver's oxygen demand is met by the hepatic portal vein, and half is met by the hepatic arteries. The hepatic artery also has both alpha- and beta-adrenergic receptors; therefore, flow through the artery is controlled, in part, by the splanchnic nerves of the autonomic nervous system. Blood flows through the liver sinusoids and empties into the central vein of each lobule. The central veins coalesce into hepatic veins, which leave
8528-530: The liver, except for the bare area , is covered in a serous coat derived from the peritoneum , and this firmly adheres to the inner Glisson's capsule. Terminology related to the liver often starts in hepat- from ἡπατο-, from the Greek word for liver. The liver is grossly divided into two parts when viewed from above – a right and a left lobe – and four parts when viewed from below (left, right, caudate , and quadrate lobes ). The falciform ligament makes
8632-421: The liver, the liver expands, and 0.5 to 1 liter of extra blood is occasionally stored in the hepatic veins and sinuses. This occurs especially in cardiac failure with peripheral congestion. Thus, in effect, the liver is a large, expandable, venous organ capable of acting as a valuable blood reservoir in times of excess blood volume and capable of supplying extra blood in times of diminished blood volume. Because
8736-429: The lobule's corners. The portal triad consists of the hepatic artery, the portal vein, and the common bile duct. The triad may be seen on a liver ultrasound, as a Mickey Mouse sign with the portal vein as the head, and the hepatic artery, and the common bile duct as the ears. Histology , the study of microscopic anatomy, shows two major types of liver cell: parenchymal cells and nonparenchymal cells. About 70–85% of
8840-552: The lymph formed in the body under resting conditions arises in the liver. The liver is a vital organ and supports almost every other organ in the body. Because of its strategic location and multidimensional functions, the liver is prone to many diseases. The bare area of the liver is a site that is vulnerable to the passing of infection from the abdominal cavity to the thoracic cavity . Liver diseases may be diagnosed by liver function tests –blood tests that can identify various markers. For example, acute-phase reactants are produced by
8944-696: The next generation. Complementarity is also utilized in DNA transcription , which generates an RNA strand from a DNA template. In addition, human immunodeficiency virus , a single-stranded RNA virus , encodes an RNA-dependent DNA polymerase ( reverse transcriptase ) that uses complementarity to catalyze genome replication. The reverse transcriptase can switch between two parental RNA genomes by copy-choice recombination during replication. DNA repair mechanisms such as proof reading are complementarity based and allow for error correction during DNA replication by removing mismatched nucleobases. In general, damages in one strand of DNA can be repaired by removal of
9048-465: The opposite sequence in the complement (ambigrams). A cDNA library is a collection of expressed DNA genes that are seen as a useful reference tool in gene identification and cloning processes. cDNA libraries are constructed from mRNA using RNA-dependent DNA polymerase reverse transcriptase (RT), which transcribes an mRNA template into DNA. Therefore, a cDNA library can only contain inserts that are meant to be transcribed into mRNA. This process relies on
9152-432: The organism, and the synthesis of proteins and various other biochemicals necessary for digestion and growth. In humans , it is located in the right upper quadrant of the abdomen , below the diaphragm and mostly shielded by the lower right rib cage . Its other metabolic roles include carbohydrate metabolism , the production of hormones , conversion and storage of nutrients such as glucose and glycogen , and
9256-541: The past by some tools. W and S denote "weak" and "strong", respectively, and indicate a number of the hydrogen bonds that a nucleotide uses to pair with its complementing partner. A partner uses the same number of the bonds to make a complementing pair. An IUPAC code that specifically excludes one of the three nucleotides can be complementary to an IUPAC code that excludes the complementary nucleotide. For instance, V (A, C or G - "not T") can be complementary to B (C, G or T - "not A"). Specific characters may be used to create
9360-429: The pores in the hepatic sinusoids are very permeable and allow ready passage of both fluid and proteins into the perisinusoidal space , the lymph draining from the liver usually has a protein concentration of about 6 g/dl, which is only slightly less than the protein concentration of plasma. Also, the high permeability of the liver sinusoid epithelium allows large quantities of lymph to form. Therefore, about half of all
9464-753: The portal vein. The expanding liver bud is colonized by hematopoietic cells . The bipotential hepatoblasts begin differentiating into biliary epithelial cells and hepatocytes. The biliary epithelial cells differentiate from hepatoblasts around portal veins, first producing a monolayer, and then a bilayer of cuboidal cells. In ductal plate, focal dilations emerge at points in the bilayer, become surrounded by portal mesenchyme, and undergo tubulogenesis into intrahepatic bile ducts. Hepatoblasts not adjacent to portal veins instead differentiate into hepatocytes and arrange into cords lined by sinusoidal epithelial cells and bile canaliculi. Once hepatoblasts are specified into hepatocytes and undergo further expansion, they begin acquiring
9568-399: The presence of ammonia. The Traube purine synthesis (1900) is a classic reaction (named after Wilhelm Traube ) between an amine -substituted pyrimidine and formic acid . In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions . Nam et al. (2018) demonstrated
9672-517: The principle of DNA/RNA complementarity. The end product of the libraries is double stranded DNA, which may be inserted into plasmids. Hence, cDNA libraries are a powerful tool in modern research. When writing sequences for systematic biology it may be necessary to have IUPAC codes that mean "any of the two" or "any of the three". The IUPAC code R (any purine ) is complementary to Y (any pyrimidine ) and M (amino) to K (keto). W (weak) and S (strong) are usually not swapped but have been swapped in
9776-399: The principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries . While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration. Complementarity
9880-400: The production of platelets by the bone marrow. The liver plays several roles in lipid metabolism: it performs cholesterol synthesis, lipogenesis , and the production of triglycerides , and a bulk of the body's lipoproteins are synthesized in the liver. The liver plays a key role in digestion, as it produces and excretes bile (a yellowish liquid) required for emulsifying fats and help
9984-412: The red bone marrow . After 2–5 days, the umbilical vein and ductus venosus are obliterated; the former becomes the round ligament of liver and the latter becomes the ligamentum venosum. In the disorders of cirrhosis and portal hypertension , the umbilical vein can open up again. Unlike eutherian mammals, in marsupials the liver remains haematopoietic well after birth. The various functions of
10088-415: The right of the fossa , between the bare area and the caudate lobe, and immediately above the renal impression. The greater part of the suprarenal impression is devoid of peritoneum and it lodges the right suprarenal gland. Medial to the renal impression is a third and slightly marked impression, lying between it and the neck of the gall bladder. This is caused by the descending portion of the duodenum, and
10192-410: The right of the gallbladder fossa are two impressions, one behind the other and separated by a ridge. The one in front is a shallow colic impression, formed by the hepatic flexure and the one behind is a deeper renal impression accommodating part of the right kidney and part of the suprarenal gland . The suprarenal impression is a small, triangular, depressed area on the liver. It is located close to
10296-403: The rings and interactions with other molecules can shift the equilibrium of these tautomers. There are many naturally occurring purines. They include the nucleotide bases adenine and guanine . In DNA , these bases form hydrogen bonds with their complementary pyrimidines, thymine and cytosine , respectively. This is called complementary base pairing. In RNA , the complement of adenine
10400-416: The sinusoidal lumen. The central area or hepatic hilum , includes the opening known as the porta hepatis which carries the common bile duct and common hepatic artery , and the opening for the portal vein. The duct, vein, and artery divide into left and right branches, and the areas of the liver supplied by these branches constitute the functional left and right lobes. The functional lobes are separated by
10504-472: The strand and a 20bp - 22bp length for a mi/siRNA, that leads to more than 1 × 10 possible combinations . Given that the human genome is ~3.1 billion bases in length, this means that each miRNA should only find a match once in the entire human genome by accident. Kissing hairpins are formed when a single strand of nucleic acid complements with itself creating loops of RNA in the form of a hairpin. When two hairpins come into contact with each other in vivo ,
10608-456: The unfolding once a favorable match has been found. Complementarity allows information found in DNA or RNA to be stored in a single strand. The complementing strand can be determined from the template and vice versa as in cDNA libraries. This also allows for analysis, like comparing the sequences of two different species. Shorthands have been developed for writing down sequences when there are mismatches (ambiguity codes) or to speed up how to read
10712-457: Was coined by the German chemist Emil Fischer in 1884. He synthesized it for the first time in 1898. The starting material for the reaction sequence was uric acid ( 8 ), which had been isolated from kidney stones by Carl Wilhelm Scheele in 1776. Uric acid was reacted with PCl 5 to give 2,6,8-trichloropurine, which was converted with HI and PH 4 I to give 2,6-diiodopurine. The product
10816-478: Was reduced to purine using zinc dust. Many organisms have metabolic pathways to synthesize and break down purines. Purines are biologically synthesized as nucleosides (bases attached to ribose ). Accumulation of modified purine nucleotides is defective to various cellular processes, especially those involving DNA and RNA . To be viable, organisms possess a number of deoxypurine phosphohydrolases, which hydrolyze these purine derivatives removing them from
#548451