VITAMINS BIOCHEMISTRY
Vitamins are micronutrients Vitamins differ from macronutrients- in structure, function and amounts. Vitamins are similar to macronutrients- all are vital to life, organic and available from all food group Both defecienies and excesses of a vitamin can affect health
Vitamins µg-mg Nutrients /day VITAMINE VITAL+ AMINE Vitamin is derived from the fact that substances are needed for life(vita) and because thiamine happened to be an amine. Not all vitamins are amines or nitrogen containing compounds
Vitamins Definition Vitamins are organic nutrients that are required in small quantities for a variety of biochemical functions and which generally cannot be synthesized in the body and must be supplied by the diet
Water soluble Fat soluble Vitamins Classification B complex C or Ascorbic acid A or Retinol D or Cholecalciferol E or Tocopherol K
VITAMINS Water soluble vitamins B1 - Thiamine B2 - Riboflavin B3 - Niacin B5 - Pantothenic acid B6 - Pyridoxine Biotin Folic acid B12- Cobalamine Vitamin B complex Vitamin C or Ascorbic acid
VITAMINS Vitamins B-complex Energy-releasing Hematopoietic Other B1 B2 Biotin Pantothenic acid Folic acid Vitamin B12 Pyridoxine
Difference b/w water soluble & fat soluble vitamins VITAMINS Water soluble vitamins Fat soluble vitamins Solubility Water soluble Fat soluble Absorption Simple Along with lipids Storage *No storage Stored in liver Excretion Excreted Not excreted Excess intake Nontoxic Toxic Deficiency Manifests rapidly Manifests slowly Treatment Regular dietary supply Single large dose
Fat soluble vitamins Vitamin A Vitamin D Vitamin E Vitamin K
vitamin
Absorption, Transport and storage VITAMIN A Chemistry Sources Daily Requirements Absorption, Transport and storage Functions Deficincy Vitamin A excess A. History.It was first recognized as an essential nutritional factor by Elmer McCollum in 1915 and then isolated from fish-liver oil by Holmes in 1917. On account of its established role in the visual process, it is often called as antixerophthalmic factor or the “bright eyes” vitamin. It was first synthesized in 1946 by Milas.
Vitamin A CHEMISTRY Retinoids Carotenes Vitamin A occurs in two forms in food Retinoids Retinol Retinal Retinoic acid Carotenes α- carotene β- carotene γ- carotene
Retinoids RETINOL β-ionone ring RETINAL RETINOIC ACID
β- carotene
Vitamin a
Sources of vitamin A
sources
Recommended daily allowance [RDA] The daily requirement of vitamin A is expressed as retinol equivalents [RE] 1000 RE MEN 800 RE WOMEN 1RE = 1µg of retinol = 3.3 IU of retinol
ABSORPTION TRANSPORT AND STORAGE VITAMIN A ABSORPTION TRANSPORT AND STORAGE
ABSORPTION TRANSPORT AND STORAGE RETINA ABSORPTION TRANSPORT AND STORAGE TARGET TISSUES
ABSORPTION TRANSPORT AND STORAGE
FUNCTIONS OF VITAMIN A Antioxidants :β -carotenes Vision : 11-cis retinal [Wald’s visual cycle] Reproduction: Retinol Growth and differentiation : Retinoic acid Epithelial Integrity : Retinol Immunity Antioxidants :β -carotenes Glycoprotein synthesis
Vitamin A and Vision RODS RHODOPSIN 11-Cis retinal Opsin Photoreceptor cells in the retina Photosensitive pigment 11-Cis retinal Opsin
Wald’s visual cycle Rhodopsin cycle comprises two distinct events Bleaching of rhodopsin & generation of nerve impulse Regeneration of rhodopsin
Wald’s visual cycle
Vitamin a and colour vision CONES Porphyropsin Iodopsin Cynopsin Photoreceptor cells in the retina Required for vision in daylight and colour identification
Vitamin a deficiency Causes Inadequate intake Impaired absorption Impaired storage & transport Increased excretion [RBP] Alcoholism
Vitamin a deficiency Features Nightblindness Xerophthalmia Bitot spots Keratomalacia Infections Hyperkeratinization of skin Growth retardation
Bitot’s spot Bitot’s spot
Xerophthalmia Keratomalacia
Diagnosis of vitamin deficiency Impaired dark adaptation time Decreased vitamin A in plasma Decreased RBP in plasma Normal plasma vitamin 20 to 80 µg/100ml
Vitamin a toxicity Over ingestion Causes Bone and joint pain Anorexia Hair loss Headache Hepatomegaly Weight loss