Basic properties

Although the vitamins included in this group are every water-soluble, the degree to which castle dissolve in water is variable. This property impacts the course of absorption, their excretion, and also their level of tissue storage and distinguishes them from fat-soluble vitamins, which are handled and stored in different ways by the body. The energetic forms and the accepted nomenclature that individual vitamin in every vitamin group are given in the table. The water-soluble vitamins are vitamin C (ascorbic acid) and the B vitamins, which incorporate thiamin (vitamin B1), riboflavin (vitamin B2), vitamin B6, niacin (nicotinic acid), vitamin B12, folic acid, pantothenic acid, and also biotin. These reasonably simple molecules contain the aspects carbon, hydrogen, and also oxygen; some additionally contain nitrogen, sulfur, or cobalt.

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The water-soluble vitamins, inactive in your so-called cost-free states, must be activated to their coenzyme forms; addition of phosphate groups occurs in the activation of thiamin, riboflavin, and vitamin B6; a shift in framework activates biotin, and formation that a complex between the cost-free vitamin and parts of various other molecules is involved in the activation that niacin, pantothenic acid, folic acid, and vitamin B12. After ~ an active coenzyme is formed, that must combine with the suitable protein component (called an apoenzyme) prior to enzyme-catalyzed reactions have the right to occur.


The B-vitamin coenzymes function in enzyme solution that transfer details groups between molecules; together a result, particular proteins, fats, and carbohydrates are formed and may be utilized to produce body tissues or to keep or release energy. The pantothenic acid coenzyme features in the tricarboxylic mountain cycle (also dubbed the Krebs, or citric acid, cycle), which interconnects carbohydrate, fat, and protein metabolism; this coenzyme (coenzyme A) acts at the hub of these reactions and thus is crucial molecule in controlling the interconversion that fats, proteins, and also carbohydrates and also their conversion into metabolic energy. Thiamin and also vitamin B6 coenzymes regulate the conversion of carbohydrates and proteins respectively into metabolic energy during the citric mountain cycle. Niacin and riboflavin coenzymes facilitate the transfer of hydrogen ions or electron (negatively charged particles), which occurs throughout the reaction of the tricarboxylic mountain cycle. All of these coenzymes also duty in carry reactions that are involved in the synthesis of structure compounds; these reactions are not component of the tricarboxylic acid cycle.


B-vitamin coenzymes in metabolism
Functions the B-vitamin coenzymes in metabolism.
Encyclopædia, Inc.

Although vitamin C participates in part enzyme-catalyzed reactions, it has not yet been established that the vitamin is a coenzyme. Its role probably is related to its properties as a solid reducing agent (i.e., it readily provides electrons to other molecules).


The water-soluble vitamins are took in in the animal intestine, pass straight to the blood, and are carried to the tissues in i beg your pardon they will certainly be utilized. Vitamin B12 needs a substance well-known as intrinsic variable in stimulate to be absorbed.

Some of the B vitamin can take place in develops that can not be provided by an animal. Most of the niacin in some grain grains (wheat, corn, rice, barley, bran), for example, is bound to one more substance, creating a complex called niacytin the cannot be took in in the animal intestine. Biotin have the right to be bound by the protein avidin, i beg your pardon is found in life egg white; this complex also cannot be soaked up or broken down by digestive-tract enzymes, and also thus the biotin cannot be utilized. In pet products (e.g., meat), biotin, vitamin B6, and also folic acid are bound to various other molecules to type complexes or conjugated molecules; although no one is energetic in the facility form, the 3 vitamins usually are released from the bound creates by the enzymes of the intestinal tract (for biotin and vitamin B6) or in the organization (for folic acid) and thus have the right to be utilized. The B vitamins are distributed in many metabolizing organization of plants and also animals.

Water-soluble vitamins usually space excreted in the urine of humans. Thiamin, riboflavin, vitamin B6, vitamin C, pantothenic acid, and biotin show up in to pee as complimentary vitamins (rather than as coenzymes); however, little free niacin is excreted in the urine. Commodities (also referred to as metabolites) that are formed throughout the management of thiamin, niacin, and vitamin B6 likewise appear in the urine. Urinary metabolites the biotin, riboflavin, and also pantothenic acid likewise are formed. Excretion of these vitamins (or your metabolites) is low as soon as intake is adequate for suitable body function. If intake begins to exceed minimal requirements, overabundance vitamins room stored in the tissues. Organization storage volume is limited, however, and, as the tissues become saturated, the price of excretion rises sharply. Unequal the various other water-soluble vitamins, however, vitamin B12 is excreted exclusively in the feces. Some folic acid and biotin also are normally excreted in this way. Although fecal excretion that water-soluble vitamin (other 보다 vitamin B12, folic acid, and also biotin) occurs, their resource probably is the minister bacteria the synthesize the vitamins, rather than vitamins that have been eaten and utilized through the animal.

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The water-soluble vitamins usually are not thought about toxic if bring away in excessive amounts. Over there is, however, one exemption in humans: large amounts (50–100 mg; 1 mg = 0.001 gram) the niacin produce dilation that blood vessels; in bigger amounts, the results are an ext serious and may an outcome in impaired liver function. Thiamin provided to pets in quantities 100 time the necessity (i.e., about 100 mg) can cause death from respiratory tract failure. Therapeutic sheep (100–500 mg) that thiamin have no well-known toxic impacts in human beings (except rarely instances that anaphylactic shock in perceptible individuals). Over there is no known toxicity for any kind of other B vitamins.