VitaminsSTRUCTURE AND FUNCTION

What are vitamins ?

Nutrients that our body does not make on its own. Thus we must obtain them from the foods we eat, or via vitaminsupplements. Several vitamins are synthesized in the intestines by bacteriums.They are essential for providing good health and are necessary for many life functions.

Vitamins are: • Tasteless, organic compounds• Required in small amounts• Functions:

Regulate metabolismHelp convert energy in fat, carbohydrate, and protein into ATPPromote growth and reproduction

• Deficiencies can result in potentially serious consequences

History of Vitamins

Disease related to deficiency and foods that help were recognized long before the vitamin was discovered.Vitamins became valued for promoting public health.1940s U.S. government mandated specific vitamins be added to grains and milk to improve health.Scientists are now focusing on prevention of disease with vitamin research.Each new vitamin is temporarily named when discoveredThe naming of vitamins follows the letters of the alphabet, starting with A; we are up to the letter K

A, B, C, D, E, and KB has many subscripts

F, G, and H were dropped

Rickets is defective mineralization of bones before epiphysealclosure in immature mammals due to deficiency or impairedmetabolism of vitamin D, phosphorus or calcium, potentially leadingto fractures and deformity.

Scurvy is a disease resulting from a deficiency of vitamin C, which isrequired for the synthesis of collagen in humans.The chemical name for vitamin C, ascorbic acid, is derived from theLatin name of scurvy, scorbutus, which also provides theadjective scorbutic

Criteria for Vitamins

• Cannot be synthesized in ample amounts in the body• Chronic deficiency is likely to cause physical symptoms• Symptoms will disappear once the vitamin level in the body is restored• Deficiency can cause permanent damage• 15 compounds meet the above criteria:

• vitamin A• Vitamin B1

• Vitamin B2

• Vitamin B3

• Vitamin B5

• Vitamin B6

• Vitamin B7

• Vitamin B9

• Vitamin B12

• Vitamin B13

• Vitamin C• Vitamin D• Vitamin E• Vitamin K• Vitamin P

Classification of VitaminsClassification is based on solubility:

Eight water-soluble: B vitamin complex and vitamin CFour fat-soluble: vitamins A, D, E, and K

Solubility influences a vitamin’s: Digestion; Absorption; Transportation; Storage; Excretion

Prosthetic vitamins Inducer vitamins

Members: Vitamin B-s and K-s A, C, D, E

Presence: In every organism In higher organisms

Function: Link to the enzymes, proteins; There have centralrole in the metabolism.

These vitamins have specific function. They arenot necessary for the life (primary metabolism) .

Synthesis in thehumans:

It can be synthesized in the intestin by bacteriums. Not synthesized in the body.

Blocking, inhibition

Inhibitors (anti-vitamins) are known! Anti-vitamins are unknown

Classification is based on biological activity:

Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, avidin is a protein in egg whites that inhibits the absorption of biotin.

• All vitamins contain carbon, hydrogen, and oxygen

• Some vitamins contain nitrogen and sulfur

• Chemical structure of each vitamin is unique

• Each vitamin is a singular unit• Vitamins are absorbed intact• Vitamins perform numerous

essential functions

Vitamin Absorption and Storage

• All absorption takes place in the small intestine• Fat-soluble vitamins Are absorbed in the duodenum

StorageVitamin A is mainly stored in the liverVitamins K and E are partially stored in the liverVitamin D is mainly stored in the fat and muscle tissue

• Water-soluble vitamins:• Absorbed with water and enter directly into the blood

stream• Most absorbed in the duodenum and jejunum• Most are not stored in the body• Excess intake excreted through the urine• Important to consume adequate amounts daily• Dietary excesses can be harmful

Can build up in body to point of toxicity!!

Digesting and Absorbing Vitamins

Digesting and Absorbing Water-Soluble Vitamins

Water-Soluble Vitamins

Fat-SolubleVitamins

Absorbed in the Small Intestine Small Intestine

Hydrophobic or Hydrophilic

Hydrophilic Hydrophobic

Absorbed into the Blood Lymph

Stored in the body Not Generally Yes

Can build up and become toxic

Not Generally Yes

Need to consume daily Yes No

Bioavailability and destruction of vitaminsAvailability based on:

• Amount in food• Preparation• Efficiency of digestion and absorption of food• Individual nutritional status• Natural or synthetic

Fat-soluble vitamins are generally less bioavailable than water-soluble vitamins.Vitamins from animal foods are generally more bioavailable than those in plant foods.

Water-soluble vitamins can be destroyed by• Exposure to air• Exposure to ultraviolet light• Water• Changes in pH• Heat• Food preparation techniques

Fat-soluble vitamins tend to be more stable

Provitamins and preformed vitamins

ProvitaminsSubstances found in foods that are not in a form directly usable by the body. Converted to the active form once absorbed

Preformed vitaminsVitamins found in foods in their active form

Vitamin A

Chemical name and provitamins: Retinol, retinal, and four carotenoids including -caroteneSolubility: fatDeficiency disease: night-blindness; hyperkeratosis; keratomaliciaOverdose disease: Hypervitaminosis AFood sources: Liver, orange, ripe yellow fruits, leafy vegetables, carrots, pumpkin, squash, spinach, fish, soy milk, milk

Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, among which beta-carotene is the most important.Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system andgood vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin toform rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision. Vitamin A alsofunctions in a very different role as retinoic acid (an irreversibly oxidized form of retinol), which is an important hormone-like growth factor for epithelial and other cells.

Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and severalprovitamin A carotenoids, among which beta-carotene is the most important. Vitamin A has multiple functions: it isimportant for growth and development, for the maintenance of the immune system and good vision. Vitamin A is needed bythe retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin the light-absorbingmolecule] that is necessary for both low-light (scotopic vision) and color vision

Scotopic vision is the vision ofthe eye under low light conditions. In thehuman eye cone cells are nonfunctional inlow light – scotopic vision is producedexclusively through rod cells which aremost sensitive to wavelengths of lightaround 498 nm (green-blue) and areinsensitive to wavelengths longer thanabout 640 nm (red). The wavelengthsensitivity is determined bythe rhodopsin photopigment.

Vitamin DChemical name and provitamins: Cholecalciferol, ErgocalciferolSolubility: fatDeficiency disease: Rickets and OsteomalaciaOverdose disease: Hypervitaminosis DFood sources: Fish, eggs, liver, mushrooms

Vitamin D is a group of fat-soluble secosteroids responsible for enhancing intestinal absorption of calcium, iron,magnesium, phosphate and zinc.

Vitamin E

Chemical name and provitamins: Tocopherols, tocotrienolsSolubility: fatDeficiency disease: Deficiency is very rare; sterility in males and abortions in females, mild hemolytic anemia in newborninfantsOverdose disease: Increased congestive heart failureFood sources: Many fruits and vegetables, nuts and seeds

Vitamin E has many biological functions, the antioxidant function being the most important and/or best known. Otherfunctions include enzymatic activities, gene expression, and neurological function(s). The most important function of vitamin Ehas been suggested to be in cell signaling (and it may not have a significant role in antioxidant metabolism)

Antioxidants activity

Antioxidant compounds neutralizes free radicals, helping to counteract the oxidation that takes place in cells. Stimulate theimmune system and interact with hormones to prevent cancers

Vitamin K

Chemical name and provitamins: phylloquinone (K1), menaquinones (K2)Solubility: fatDeficiency disease: Bleeding diathesisOverdose disease: Increases coagulation in patientsFood sources: Leafy green vegetables such as spinach, egg yolks, liver

Vitamin K is a group of structurally similar, fat-soluble vitamins that the human body needs for modification of certain proteinsthat are required for blood coagulation, and in bone and other tissue. The modification of the proteins allows them tobind calcium ions. Vitamin K1 can be found just in the plants. K2 is produced in bacteria, including the type of bacteria found inhuman and animal intestines.Vitamin K is necessary for proper blood clots to form. The clotting process is exceptionally complex, requiring at least 12proteins to function before the process is complete. Four of these clotting factors require vitamin K for their activity.Vitamin K is necessary for the activation of a protein called osteocalcin. This protein is used in the mineralization of bone, aprocess by which calcium and other minerals are added to the structural protein matrix.

Vitamin B1

Chemical name and provitamins: thiamineSolubility: waterDeficiency disease: Beriberi, Wernicke-Korsakoff syndromeOverdose disease: Drowsiness or muscle relaxation with large dosesFood sources: Pork, oatmeal, brown rice, vegetables, potatoes, liver, eggs

Its phosphate derivatives are involved in many cellular processes. The best-characterized form is thiaminepyrophosphate (TPP), a coenzyme in the catabolism of sugars and amino acids. Thiamine is used in the biosynthesis of theneurotransmitter acetylcholine and gamma-aminobutyric acid (GABA). In yeast, TPP is also required in the first stepof alcoholic fermentation.All living organisms use thiamine, but it is synthesized only in bacteria, fungi, and plants. Animals must obtain it from theirdiet, and thus, for them, it is an essential nutrient.

Vitamin B2

Chemical name and provitamins: RiboflavinSolubility: waterDeficiency disease: Ariboflavinosis, Glossitis, Angular stomatitisOverdose disease: unknownFood sources: milk, chees, dairy products, bananas, popcorn, green beans, asparagus

It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a wide variety of cellular processes. It plays a key role in energy metabolism, and for the metabolism of fats, ketone bodies, carbohydrates, and proteins.

Vitamin B3

Chemical name and provitamins: Niacin, niacinamideSolubility: waterDeficiency disease: PellagraOverdose disease: Liver damage (doses > 2g/day)Food sources: Meat, fish, eggs, many vegetables, mushrooms, tree nuts

Niacin cannot be directly converted to nicotinamide, but both compounds are precursors of the coenzymes nicotinamideadenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) in vivo. NAD converts to NADP byphosphorylation in the presence of the enzyme NAD+ kinase. NADP and NAD are coenzymes for many dehydrogenases,participating in many hydrogen transfer processes. NAD is important in catabolism of fat, carbohydrate, protein, and alcohol,as well as cell signaling and DNA repair, and NADP mostly in anabolism reactions such as fatty acid and cholesterol synthesis.

Vitamin B5

Chemical name and provitamins: Pantothenic acidSolubility: waterDeficiency disease: ParesthesiaOverdose disease: Diarrhea; possibly nausea and heartburnFood sources: Meat, broccoli, avocados

For many animals, pantothenic acid is an essential nutrient. Animals require pantothenic acid to synthesize coenzyme-A (CoA),as well as to synthesize and metabolize proteins, carbohydrates, and fats.

Age group Age Requirements

Infants 0–6 months 1.7 mg

Infants 7–12 months 1.8 mg

Children 1–3 years 2 mg

Children 4–8 years 3 mg

Children 9–13 years 4 mg

Adult men and women 14+ years 5 mg

Pregnant women (vs. 5) 6 mg

Breastfeeding women (vs. 5) 7 mg

Vitamin B6

Chemical name and provitamins: Pyridoxine, pyridoxamine, pyridoxalSolubility: waterDeficiency disease: Anemia, peripheral neuropathyOverdose disease: Impairment of proprioception, nerve damageFood sources: Meat, vegetables, tree nuts, bananas

Vitamin B6 is a water-soluble vitamin and is part of the vitamin B complex group. Several forms of the vitamin are known,but pyridoxal phosphate (PLP) is the active form and is a cofactor in many reactions of amino acid metabolism, includingtransamination, deamination, and decarboxylation. PLP also is necessary for the enzymatic reaction governing the releaseof glucose from glycogen.In 1934 a Hungarian physician Paul Gyorgy discovered a substance that was able to cure a skin disease in rats (dermititisacrodynia). Enzymes dependent on PLP focus a wide variety of chemical reactions mainly involving amino acids. The reactions carried out by the PLP-dependent enzymes that act on amino acids include transfer of the amino group, decarboxylation, racemization, and beta- or gamma-elimination or replacement. Such versatility arises from the ability of PLP to covalently bind the substrate,and then to act as an electrophilic catalyst, thereby stabilizing different types of carbanionic reaction intermediates.

Vitamin B7

Chemical name and provitamins: BiotinSolubility: waterDeficiency disease: Dermatitis, enteritisOverdose disease: UnkmownFood sources: Raw egg yolk, liver, peanuts, leafy green vegetables

Biotin, also known as vitamin H or coenzyme R, is a water-soluble B-vitamin (vitamin B7). It is composed of a ureido(tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbonatoms of the tetrahydrothiophene ring. Biotin is a coenzyme for carboxylase enzymes, involved in the synthesis of fatty acids,amino acids (isoleucine, and valine), and in gluconeogenesis.

Vitamin B9

Chemical name and provitamins: Folic acid, folinic acidSolubility: waterDeficiency disease: Megaloblastic anemia.Deficiency during pregnancy is associated with birth defects, such as neural tubedefectsOverdose disease: May mask symptoms of vitamin B12 deficiencyFood sources: Leafy vegetables, pasta, bread, cereal, liver

Vitamin B9 (folate converted from folic acid) is essential for numerous bodily functions. Humans cannot synthesize folate denovo; therefore, folate has to be supplied through the diet to meet their daily requirements. The human body needs folate tosynthesize DNA, repair DNA, and methylate DNA as well as to act as a cofactor in certain biological reactions. It is especiallyimportant in aiding rapid cell division and growth, such as in infancy and pregnancy. Children and adults both require folateto produce healthy red blood cells and prevent anemia.

Vitamin B12

Chemical name and provitamins: Cyanocobalamin, hydroxycobalamin, methylcobalaminSolubility: waterDeficiency disease: Megaloblastic anemiaOverdose disease: Acne-like rashFood sources: Meat and other animal products

It is a water-soluble vitamin with a key role in the normalfunctioning of the brain and nervous system, and for theformation of blood. It is normally involved in the metabolism ofevery cell of the human body, especiallyaffecting DNA synthesis and regulation, but also fattyacid synthesis (especially odd chain fatty acids) and energyproduction. Neither fungi, plants, nor animals are capable ofproducing vitamin B12. Only bacteria and archaea have theenzymes required for its synthesis, although many foods are anatural source of B12 because of bacterial symbiosis. Thevitamin is the largest and most structurally complicated vitaminand can be produced industrially only through bacterialfermentation-synthesis.

Vitamin B13Chemical name and provitamins: Orotic acidSolubility: waterDeficiency disease: UnknownOverdose disease: UnknownFood sources: root vegetables, such as carrots and beets as well as liquid whey.

Orotic acid (vitamin B13) is not really recognized as a vitamin, and is manufactured by the body by intestinal flora. Antioxidant,and protect the liver from damage; promotes the treatment of sclerosis multiplex

Vitamin PChemical name and provitamins: rutin; rutosideSolubility: waterDeficiency disease: UnknownOverdose disease: UnknownFood sources: orange, grapefruit, lemon, lime; apple

Rutin inhibits platelet aggregation, as well as decreases capillary permeability, making the blood thinner and improving circulation, shows anti-inflammatory activity in some animal and in vitro models, inhibits aldose reductase. Aldose reductase is an enzyme normally present in the eye and elsewhere in the body. It helps change glucose into the sugar alcohol sorbitol.Recent studies show rutin could help prevent blood clots, so could be used to treat patients at risk of heart attacks and strokes.

Vitamin C

Chemical name and provitamins: Ascorbic acidSolubility: waterDeficiency disease: ScurvyOverdose disease: Vitamin C megadosage, cronic diarrheaFood sources: Many fruits and vegetables, liver

Albert Szent-Györgyi 1893-1986

Nobel Prize - 1937

Vitamin C is a cofactor in at least eight enzymatic reactions, includingseveral collagen synthesis reactions that, when dysfunctional, cause the most severesymptoms of scurvy. In animals, these reactions are especially important in wound-healingand in preventing bleeding from capillaries.The biological role of ascorbate is to act as a reducing agent, donating electrons to variousenzymatic and a few non-enzymatic reactions. The one- and two-electron oxidized forms ofvitamin C, semi-dehydroascorbic acid and dehydroascorbic acid, respectively, can be reducedin the body by glutathione and NADPH-dependent enzymatic mechanisms. The presence ofglutathione in cells and extracellular fluids helps maintain ascorbate in a reduced state.