Vitamin B12 in the context of "Nutritional yeast"

The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 6.5 metres (21 feet) long and folds many times to fit in the abdomen. Although it is longer than the large intestine, it is called the small intestine because it is narrower in diameter.

The small intestine has three distinct regions – the duodenum, jejunum, and ileum. The duodenum, the shortest, is where preparation for absorption through small finger-like protrusions called intestinal villi begins. The jejunum is specialized for the absorption through its lining by enterocytes of small nutrient particles which have been previously digested by enzymes in the duodenum. The main function of the ileum is to absorb vitamin B₁₂, bile salts, and whatever products of digestion were not absorbed by the jejunum.

Lesch–Nyhan syndrome (LNS) is a rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This deficiency occurs due to mutations in the HPRT1 gene located on the X chromosome. LNS affects about 1 in 380,000 live births. The disorder was first recognized and clinically characterized by American medical student Michael Lesch and his mentor, pediatrician William Nyhan, at Johns Hopkins.

The HGPRT deficiency causes a build-up of uric acid in all body fluids. The combination of increased synthesis and decreased utilization of purines leads to high levels of uric acid production. This results in both high levels of uric acid in the blood and urine, associated with severe gout and kidney problems. Neurological signs include poor muscle control and moderate intellectual disability. These complications usually appear in the first year of life. Beginning in the second year of life, a particularly striking feature of LNS is self-mutilating behaviors, characterized by lip and finger biting. Neurological symptoms include facial grimacing, involuntary writhing, and repetitive movements of the arms and legs similar to those seen in Huntington's disease. The cause of the neurological abnormalities remains unknown. Because a lack of HGPRT causes the body to poorly utilize vitamin B₁₂, some males may develop megaloblastic anemia.

Roe, (/roʊ/ ROH) or hard roe, is the fully ripe internal egg masses in the ovaries, or the released external egg masses, of fish and certain marine animals such as shrimp, scallop, sea urchins and squid. As a seafood, roe is used both as a cooked ingredient in many dishes, and as a raw ingredient for delicacies such as caviar.

The roe of marine animals, such as the roe of lumpsucker, hake, mullet, salmon, Atlantic bonito, mackerel, squid, and cuttlefish are especially rich sources of omega-3 fatty acids, but omega-3s are present in all fish roe. Also, a significant amount of vitamin B₁₂ is among the nutrients present in fish roes.

The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are connected to one another. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike other chemical formula types, which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a more complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same molecular formula. There are multiple types of ways to draw these structural formulas such as: Lewis structures, condensed formulas, skeletal formulas, Newman projections, Cyclohexane conformations, Haworth projections, and Fischer projections.

Several systematic chemical naming formats, as in chemical databases, are used that are equivalent to, and as powerful as, geometric structures. These chemical nomenclature systems include SMILES, InChI and CML. These systematic chemical names can be converted to structural formulas and vice versa, but chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the structural changes that occur in them during chemical reactions. ChemSketch and ChemDraw are popular downloads/websites that allow users to draw reactions and structural formulas, typically in the Lewis Structure style.

Beef is the culinary name for meat from cattle (Bos taurus). Beef can be prepared in various ways; cuts are often used for steak, which can be cooked to varying degrees of doneness, while trimmings are often ground or minced, as found in most hamburgers. Beef contains protein, iron, and vitamin B12. Along with other kinds of red meat, high consumption is associated with an increased risk of colorectal cancer and cardiovascular disease, especially when processed. Beef has a high environmental impact, being a primary driver of deforestation with the highest greenhouse gas emissions of any agricultural product.

In prehistoric times, humans hunted aurochs and later domesticated them. Since that time, numerous breeds of cattle have been bred specifically for the quality or quantity of their meat. Today, beef is the third most widely consumed meat in the world, after pork and poultry. As of 2018, the United States, Brazil, and China were the largest producers of beef.

The ileum (/ˈɪliəm/) is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum. Its main function is to absorb vitamin B₁₂, bile salts, and whatever products of digestion that were not absorbed by the jejunum.

The ileum follows the duodenum and jejunum and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2–4 m long, and the pH is usually between 7 and 8 (neutral or slightly basic).

Dorothy Mary Crowfoot Hodgkin OM FRS HonFRSC (née Crowfoot; 12 May 1910 – 29 July 1994) was an English chemist who advanced the technique of X-ray crystallography to determine the structure of biomolecules, which became essential for structural biology. She received the 1964 Nobel Prize in Chemistry, and is the only British woman scientist to have been awarded a Nobel Prize.

Among her most influential discoveries are the confirmation of the structure of penicillin as previously surmised by Edward Abraham and Ernst Boris Chain; and mapping the structure of vitamin B₁₂, for which in 1964 she became the third woman to win the Nobel Prize in Chemistry. Hodgkin also elucidated the structure of insulin in 1969 after 35 years of work.