Given the question: Information: - Urobilinogen is a colourless by - product of bilirubin reduction . It is formed in the intestines by bacterial action on bilirubin . About half of the urobilinogen formed is reabsorbed and taken up via the portal vein to the liver , enters circulation and is excreted by the kidney . Increased amounts of bilirubin are formed in hemolysis , which generates increased urobilinogen in the gut . In liver disease ( such as hepatitis ) , the intrahepatic urobilinogen cycle is inhibited also increasing urobilinogen levels . Urobilinogen is converted to the yellow pigmented urobilin apparent in urine . The urobilinogen in the intestine is directly reduced to brown stercobilin , which gives the feces their characteristic color . It can also be reduced to stercobilinogen , which can then be further oxidized to stercobilin . This constitutes the normal '' enterohepatic urobilinogen cycle '' . In biliary obstruction , below - normal amounts of conjugated bilirubin reach the intestine for conversion to urobilinogen . With limited urobilinogen available for reabsorption and excretion , the amount of urobilin found in the urine is low . High amounts of the soluble conjugated bilirubin enter the circulation where they are excreted via the kidneys . These mechanisms are responsible for the dark urine and pale stools observed in biliary obstruction . Low urine urobilinogen may result from complete obstructive jaundice or treatment with broad - spectrum antibiotics , which destroy the intestinal bacterial flora . ( Obstruction of bilirubin passage into the gut or failure of urobilinogen production in the gut . ) Low urine urobilinogen levels may result from congenital enzymatic jaundice ( hyperbilirubinemia syndromes ) or from treatment with drugs that acidify urine , such as ammonium chloride or ascorbic acid . Elevated levels may indicate hemolytic anaemia ( excessive breakdown of red blood cells RBC ) , overburdening of the liver , increased urobilinogen production , re-absorption - a large hematoma , restricted liver function... - Bilirubin (formerly referred to as haematoidin and discovered by Rudolf Virchow in 1847) is a yellow compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the destruction of aged red blood cells. First the hemoglobin gets stripped of the heme molecule which thereafter passes through various processes of porphyrin catabolism, depending on the part of the body in which the breakdown occurs. For example, the molecules excreted in the urine differ from those in the feces. The production of biliverdin from heme is the first major step in the catabolic pathway, after which the enzyme biliverdin reductase performs the second step, producing bilirubin from biliverdin. - Porphyrins are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their carbon atoms via methine bridges (=CH). The parent porphyrin is porphin, and substituted porphines are called porphyrins. The porphyrin ring structure is aromatic, with a total of 26 electrons in the conjugated system. Various analyses indicate that not all atoms of the ring are involved equally in the conjugation or that the molecule's overall nature is substantially based on several smaller conjugated systems. One result of the large conjugated system is that porphyrin molecules typically have very intense absorption bands in the visible region and may be deeply colored; the name "porphyrin" comes from the Greek word ("porphyra"), meaning "purple". - Urobilin or urochrome is the chemical primarily responsible for the yellow color of urine. It is a linear tetrapyrrole compound that, along with the related compound urobilinogen, are degradation products of the cyclic tetrapyrrole heme. - Rudolf Ludwig Carl Virchow (13 October 1821 5 September 1902) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician, known for his advancement of public health. He is known as "the father of modern pathology" because his work helped to discredit humourism, bringing more science to medicine. He is also known as the founder of social medicine and veterinary pathology, and to his colleagues, the "Pope of medicine". - Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 64,000 species described. Vertebrates include the jawless fish and the jawed vertebrates, which include the cartilaginous fish (sharks and rays) and the bony fish. - Red blood cells (RBCs), also called erythrocytes, are the most common type of blood cell and the vertebrate's principal means of delivering oxygen (O) to the body tissuesvia blood flow through the circulatory system. RBCs take up oxygen in the lungs, or gills of fish, and release it into tissues while squeezing through the body's capillaries. - Feces or faeces are the solid or semisolid metabolic waste from an animal's digestive tract, discharged through the anus or cloaca during a process called defecation. Urine and feces together are called excreta. - Biliverdin is a green tetrapyrrolic bile pigment, and is a product of heme catabolism. It is the pigment responsible for a greenish color sometimes seen in bruises. - Heme or haem (from Greek "haima" meaning blood) is a cofactor consisting of an Fe (ferrous) ion contained in the centre of a heterocyclic macrocycle organic compound called a porphyrin, made up of four pyrrolic groups joined together by methine bridges. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are known as hemoproteins. Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin, cytochrome, catalase, heme peroxidase, and endothelial nitric oxide synthase. - Hemoglobin; also spelled haemoglobin (United Kingdom spelling) and abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates (with the exception of the fish family Channichthyidae) as well as the tissues of some invertebrates. Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the rest of the body (i.e. the tissues). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism. - Biliverdin reductase (BVR) is an enzyme found in all tissues under normal conditions, but especially in reticulo-macrophages of the liver and spleen. BVR facilitates the conversion of biliverdin to bilirubin via the reduction of a double-bond between the second and third pyrrole ring into a single-bond. - Urine is a liquid by-product of metabolism in the bodies of many animals, including humans. It is expelled from the kidneys and flows through the ureters to the urinary bladder, from which it is soon excreted from the body through the urethra during urination. - Enzymes are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions. The molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life. The set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called "enzymology". After reading the paragraphs above, we are interested in knowing the entity with which 'urobilinogen' exhibits the relationship of 'has part'. Find the answer from the choices below. Choices: - 1902 - a - blood - carbon - cell - e - family - fish - group - he - iron - liquid - liver - order - oxygen - product - s - set - solid - system - third - united kingdom - vein
The answer is:
carbon