vitamins- انوار.pdf

Ass.prof. Dr. Anwar Alabdali  Vitamins By the ends of the lectures you will learn What are the vitamins ? Classification of vitamins Function of vitamins Deficiency of vitamins Signs and symptoms Where the vitamins are found ? ...

Ass.prof. Dr. Anwar Alabdali  Vitamins By the ends of the lectures you will learn What are the vitamins ? Classification of vitamins Function of vitamins Deficiency of vitamins Signs and symptoms Where the vitamins are found ?  Vitamins - Vitamins are chemically organic compounds - They cannot be synthesized in adequate quantities by humans and, therefore, must be supplied by the diet. - They are classified as water-soluble and fat-soluble. - Vitamins are required to perform specific cellular functions, for example, many of the water- soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. - Fat-soluble vitamin are released, absorbed, and transported with the fat of the diet. - They are not readily excreted in the urine, and significant quantities are stored in the liver and adipose tissue. - consumption of vitamins A and D in excess of the Dietary Reference Intakes (DRIs) can lead - to accumulation of toxic quantities of these compounds.  Classification of Vitamins Water-soluble Fat-soluble Vit.A(retinol,β-carotenes) Non-B-Complex B-Complex Vit.D(cholecalciferol) Vit.K(phylloquinones, Ascorbic acid menaquinones) (vit. C) Energy-releasing Other Vit.E (tocopherols) Hematopoietic Thiamine(vit.B1) Pyridoxine( vit.B6) Folic acid Pyridoxal Riboflavin(vitaminB2) vitaminB12 Niacin(vit.B3) pyridoxamine Biotin Pantothenic acid  Folic acid Active form :- Tetrahydro-folic acid Function :-Transfer one-carbon units Synthesis of methionine, purines, and thymidine monophosphate. Deficiency:-Megaloblastic anemia (Anemia is a condition in which the blood has a lower than normal concentration of hemoglobin, which results in a reduced ability to transport oxygen). called megaloblastic because a deficiency of folic acid or vitamin B12 causes accumulation of large, immature red cell precursors, known as megaloblasts, in the bone marrow and the blood. Neuraltube defects (Spina bifida and anencephaly) (abnormal development of part of the spine and spinal cord) and anencephaly (severely abnormal development of the brain). Women should be supplemented with Folic acid before conception and during the first trimester to reduce the defects. Therefore, all women of childbearing age are advised to consume 0.4 mg/day of folic acid to reduce the risk of having a pregnancy affected by neural tube defects  Folic acid Signs and symptoms :- Anemia Birth defects Toxicity:- None  Vitamin B12 Other name:- Cobalamin Active form :- MethylcobalaminDeoxyadenosylcobalamin Function:- Coenzyme for reactions Homocysteine → methionine Methylmalonyl CoA → succinyl CoA  Vitamin B12 Deficiency :-Pernicious anemia Dementia Spinal degeneration Signs and symptoms :- Megaloblastic anemia Neuropsychiatric symptoms Toxicity:- None Vit.B12 presents in liver ,whole milk. Eggs, oysters. Fresh shrimp, pork and chicken  Vitamin C Other name :- Ascorbic acid Active form:- Ascorbic acid Function :- Antioxidants (are substances that can prevent or slow damage to cells caused by free radicals). Cosumption of diets rich in vit. C is associated with a decreased incidence of some chronic diseases such as coronary heart disease and certain cancers. - Coenzyme for hydroxylation reactions, for example: In procollagen: Proline → hydroxyproline Lysine → hydroxylysine - Vit. C is required for the maintenance of normal connective tissue - For wound healing - It facilitates the absorption of dietary iron from the intestine.  Vitamin C Deficiency :- Scurvy Signs and symptoms :- Sore, spongy gums ,Loose teeth, fragile blood vessels and Poor wound healing , also swollen joints and anemia Toxicity :- None *Vit C is present in  Vitamin B6 Other name: - Pridoxin , pyridoxal , pyridoxamine Active form :- Pyridoxal phosphate Function :- Coenzyme for enzymes, particularly in amino acid metabolism e.g. Deamination Serine → pyruvate + NH3 Decarboxylation Histidine → histamine + CO2 Deficiency :- are rare but it has been observed in new-born infants fed formulas low in B6 in women taking oral contraceptives and in alcoholics. * Isoniazid a drug is used to treat tuberculosis, can induce a vitamin B6 deficiency. Clinical signs and symptoms :- Glositis , neuropathy, microcytic anemia (due to impaired heme synthesis) Vitamin B6 is present in Fish , beef liver and other organ meat also in potatoes and other starchy vegetables  Vitamin B1 Other name:- Thiamine Active form:- Thiamine pyrophosphate Function:- Coenzyme of enzymes catalyzing: Pyruvate → acetyl CoA α-Ketoglutarate → Succinyl CoA Ribose 5-P + xylulose 5-P → Sedoheptulose 7-P + Glyceraldehyde 3-P Branched-chain amino acid oxidation Deficiency:- Beriberi ,Wernicke-Korsakoff syndrome (most common in alcoholics) Signs and symptoms:- Tachycardia, vomiting, convulsions ,Apathy, loss of memory, eye movements This vitamin is found in beef,liver,dried milk, nuts,oats, oranges,pork, eggs, legumes  Niacin/Vitamin B3 Other name :- Nicotinic acid Nicotinamide Active form :- NAD+, NADP+ Function:-Electron transfer NAD+ and NADP+ serve as coenzymes in oxidation-reduction reactions in which the coenzyme undergoes reduction of the pyridine ring by accepting a hydride ion (hydrogen atom plus one electron). The reduced forms of NAD+ and NADP+ are NADH and NADPH, respectively. Deficiency:- Pellagra Signs and symptoms:- Dermatitis, Diarrhea, Dementia * Niacin is present in grains and cereal, milk ,liver.(Corn is low in niacin )  Vitamin B2 Other name :- Riboflavin Active form:- FMN, FAD Function:- Electron transfer Deficiency:- Rare Signs and symptoms:- Dermatitis, Angular stomatitis Vitamin B2 is present in dairy milk ,yogurt,cheese,eggs,chicken breast, salmon  Biotin active form:- Enzyme-bound biotin function :- Carboxylation reactions Deficiency :- does not occur naturally because :- The vitamin is widely distributed in food. A large percentage of the biotin requirement in humans is supplied by intestinal bacteria. The addition of raw egg white to the diet as a source of protein induces symptoms of biotin deficiency, namely, dermatitis, glossitis, loss of appetite, and nausea. Raw egg white contains a glycoprotein, avidin, which tightly binds biotin and prevents its absorption from the intestine.  Pantothenic acid active form :- Coenzyme A function :- Acyl carrier Pantothenic acid has two roles in the body: 1. It is part of coenzyme A (CoA) 2. It is part of acyl carrier protein (Most pantothenic acid in food is found as CoA) CoA contains a thiol group that carries acyl compounds as activated thiol esters. Examples of such structures are succinyl CoA, fatty acyl CoA, and acetyl CoA. Deficiency is not well characterized in humans  Vitamin A Other name:- Retinol Retinal Retinoic acid β-Carotene Active form :- Retinol Retinal Retinoic acid Function:- Maintenance of reproduction Vision Promotion of growth Differentiation and maintenance of epithelial tissues Gene expression Actions of retinoid Deficiency :- infertility , Night blindness ,Retardation of growth Xerophthalmia (a pathologic dryness of the conjunctiva and cornea). Symptoms:- Increased visual threshold Dryness of cornea Toxicity:- Amounts exceeding 7.5 mg/day of retinol is a toxic and should be avoided. Excessive intake of vitamin A produces a toxic syndrome called hypervitaminosisA. Which is characterized by the following signs:- Skin(becomes dry and pruritic due to decrease of keratin synthesis The liver, which becomes enlarged and can become cirrhotic Vitamin A is present in :- Liver, kidney, cream, butter, and egg yolk are good sources of preformed vitamin A. Yellow and dark green vegetables and fruits are good dietary sources of the carotenes, which serve as precursors of vitamin A.  Vitamin D Other name:- Cholecalciferol, Ergocalciferol Active form :- 1,25-Dihydroxycholecalciferol Function :- Calcium uptake Deficiency:- Rickets (in children) Osteomalacia (in adults) Sign and symptoms : - Soft, pliable bones Toxicity :- High doses (100,000 IU for weeks or months) can cause loss of appetite, nausea, thirst, and stupor. Enhanced calcium absorption and bone resorption results in hypercalcemia, which can lead to deposition of calcium in many organs, particularly the arteries and kidneys. ** Vitamin D occurs naturally in fatty fish, liver, and egg yolk. Milk, Response to low plasma calcium  Vitamin k Other name:- phylloquinone (in plants ) (or vitamin K1) Menaquinone (or vitamin K2) (in intestinal bacterial flora) Menadione ( A synthetic form of vitamin K) Active form :- Menadione Menaquinone Phylloquinon Function :- γ-Carboxylation of glutamate residue in clotting and other proteins Deficiency:-Newborn, rare in adults hypoprothrombinemia Sign and symptoms :- Bleeding ***Vitamin K is found in cabbage, kale, spinach, egg yolk, and liver. There is also extensive synthesis of the vitamin by the bacteria in the gut.  Vitamin E Other name:- α-Tocopherol Active form :-Any of several tocopherol derivatives Function :- Antioxidant Deficiency:-Rare Sign and symptoms:- Red blood cell fragility leads to hemolytic anemia ****Vegetable oils are rich sources of vitamin E, whereas liver and eggs contain moderate amounts.