VITAMINS Organic compounds required in the diet in small amount to perform specific biological functions for the maintenance.of optimum growth and health :Classification.Fat soluble Vit Water A,D, E, K Soluble vit B, C
Fat soluble vit are solule in fat,oil and in,fat solvents like alcohol, acetone In general fat S. Vit. are stored in liver and excreted through the bile, and excess consumption of these vit particularly A and D lead to accumulation and toxic effect Hypervitaminosis
Water soluble vit. are readily excreted in.urine and they are relatively less toxic Water soluble vit are not stored in the body ).(except vit B12 Generally vit deficiency are multiple rather.than single deficiency
:Vit A Water soluble vit.,stable at high temp, cannot synthesize in the body,must be supplied by.diet.sources: vit, pro vit )Pro vit: (B- carotene B-Carotene: it is part of the pigment of green and yelow.vegetables After absorption from the gut it will be converted into active
It is more important that vit B- carotene can be converted into 2.molecules of vit A in the intestinal mucosa Carots Retinal molecules )form Intest mucose,reduction Retinol(alcohol Retinol absorbed from intest mucose then esterified with fatty acid and transported to the liver.retinol is then transport to the blood stream in associatation with Retinol binding ).protein(rbp
Schematic presentation of metabolic pathways )of retinol (VitA
:Biochemical Functions support the growth and the integrity of 1.Epith. T.,skin eyes, bronchus& testis In Eye absence or reduced vit A may lead to replacement of normal Epith. tissue by keratinized tissue which are more susceptible to invasion by microorganism.xerophthalmia progress to blindness Mediating vision as a constituent of the 2.pigment called rhodopsin Anti-carcinogenic effect 3.Antioxidant effect 4
:Effect of Vit A on vision Rhodopsin Rods, cones Rhodopsin on exposure to light is 1 isomerized through several steps t form trans-retinal and by spontinous hydrolysis.to form opsin The trans retinal is immedately 2 isomerized by an enzyme retinal isomerase.in the pigment of the retina to cis retinal
cis retinal bind to opsin spontaneously to 3 form rhodopsin and this complete the visual.cycle some of the trans-retinal my be reduced to 4 trans retinol and temporarily stored in the.pigment epith cells of the retina 5This trans retinal along with trans retionl from food or from that stored in the liver.must be converted to cis retinal
This cis retinal can combine with opsin to 6.form rhodopsin See the diagram :Deficiency nightblinfness.keratomalcia 2 Xerophthalmia& 3Increase risk of developing cancer 1
)Vit D ( Antirachitic vit It is now considered a a hormone rather than vit.it is a derivative of 7 dehydrocholesterol pro-vitd) when subjected to light acquired the( physiological property of curing and preventing.richet Vit D is asteroid prohormone by various metabolic changes in the body they give rise to a hormone )calcitriol(
Metabolism;vit D from sun exposure or from diet after absorption from the intestine,transported in the lymphatics then circulate in the blood to bind to certain type of protein calledvitd binding protein Vit D takn by the liverto be hydroxylated in.position 25 by enzyme vitd 25 hydroxylase In the kidney another hydroxylation at.position 1 1 hydroxylase enzyme Resulting in a compound called
)dihydroxycholecalciferol (active form 1,25.Calcitriol
Metabolic pathway of.vit D Synthesis of 1,25 dihydroxycholecalcife )rol(active vit D
:Functions It regulates calcium,po4 metabolism 1 through the active form of vitd,ie it increase the absorption of calcium po4, from the.intestinal mucose It infleunce the handeling of phosphate by. 2.the kidney Decrease vitd lead to decrease in the.excretion of phosphate dihydroxy cholecalciferol increase 1,25 3 bone resorpton producing rise in calcium, this is mediated through parathyroid horone
Under the condition of hypocalcemia there is increase secretion in of PTH which in turn stimulate the synthesis of 1,25 Di OH chole In the kidney.this mobilize calcium from the bone lead to rise in calcium and this high calcium supress the PTH through feedback.mechnism. Suppress further 1,25
: Deficiency Occur due to inadequate exposure to sun light or inadequate intake as in.pregnancy and lactation Ricket Osteomalcia infant&children Adult
:Vit E :α tocopherol Found in animal and plant fat and oil, fat.soluble vit stable to heat and acid Sources: plant and animal tissues, cotton seed oil,corn oil,soyabean oil,sunflower,..oil,fish,egg :Functions :Biological Antioxidants 1 Vit E along with Vit C important in 2 preventing damage to lung tissuefrom.oxidant in air
It prevents the oxidation of various 3.compound particularly fat Vit E may play a role in the 4 development of anemia in infant ).( macrocytic anemia.antisterility effect 5.Vit.E has a sparing action on vit A Def 6 : sterilty Damage to the liver& lung tissues. Rancidity of oil.anemia in infant
.)Vit.K: (Antihemorrhagic vit Fat soluble vit.,green vegetables, cabbage,.cauriflower,spinach,cheese,dairy product It also synthesized by the microrganism )(intestinal flora forms Menadione K3 3 MenaquinoneK2 PhylloquinoneK1
:Absorption.Require bile salts for its absorption Deficiency occurs if bile is prevented from.entering the intestine Sterilization of bowel.prolonged administration of antibiotics
:Functions vit k has been shown to be involved in the 1 maintenance of normal level of blood clotting factor.ii VII IX X It catalyze the synthesis of prothrombin in 2.the liver Absence of vit k, hypo prothrombinemia.occurs and blood clotting time is prolonged ).Anti dote to some drugs(warfarin. 3