Coupon Accepted Successfully!



  1. Vitamins & essential minerals are required for normal growth, development, maintenance of health.
  2. They can be not synthesized by human tissues but must be included in diet.
  3. Classification –     
    1. water soluble vitamins; 
    2.  fat soluble vitamins

Water soluble vitamins are:

Fat soluble vitamins are:

1.       Vitamin C (ascorbic acid)

1.   Vitamin A

2.       Vitamin B complex group includes

2.   Vitamin D

i.       Vitamin B1 (thiamine)

3.   Vitamin E

ii.       Vitamin B2 (riboflavin)

4.   Vitamin K

iii.       Niacin (Nicotinic acid)


iv.       Vitamin B6 (Pyridoxine)


v.       Pantothenic acid


vi.       α-Lipoic Acid


vii.       Biotin


viii.       Folic acid


ix.     Vitamin B12



Table: The Vitamins (Harper 28th edition, Pg 468)




Deficiency disease



Retinol, β-carotene

Visual pigments in the retina; regulation of gene expression and cell differentiation (β-carotene is an antioxidant)

Night blindness, xerophthalmia; keratinization of skin



Maintenance of calcium balance; enhances intestinal absorption of Ca2+ and mobilizes bone mineral; regulation of gene expression and cell differentiation

Rickets = poor mineralization of bone; osteomalacia = bone demineralization


Tocopherols, tocotrienols

Antioxidant, especially in cell membranes; roles in cell signaling

Extremely rare—serious neurologic dysfunction


Phylloquinone: menaquinones

Coenzyme in formation of γ-carboxyglutamate in enzymes of blood clotting and bone matrix

Impaired blood clotting, hemorrhagic disease




Coenzyme in pyruvate and α-ketoglutarate dehydrogenases, and transketolase; regulates Cl channel in nerve conduction

Peripheral nerve damage (beriberi) or central nervous system lesions (Wernicke-Korsakoff syndrome)



Coenzyme in oxidation and reduction reactions (FAD and FMN); prosthetic group of flavoproteins

Lesions of corner of mouth, lips, and tongue, seborrheic dermatitis


Nicotinic acid, nicotinamide

Coenzyme in oxidation and reduction reactions, functional part of NAD and NADP; role in intracellular calcium regulation and cell signaling

Pellagra—photosensitive dermatitis, depressive psychosis


Pyridoxine, pyridoxal, pyridoxamine

Coenzyme in transamination and decarboxylation of amino acids and glycogen phosphorylase; modulation of steroid hormone action

Disorders of amino acid metabolism, convulsions


Folic acid

Coenzyme in transfer of one-carbon fragments

Megaloblastic anemia



Coenzyme in transfer of one-carbon fragments and metabolism of folic acid

Pernicious anemia = megaloblastic anemia with degeneration of the spinal cord


Pantothenic acid

Functional part of CoA and acyl carrier protein: fatty acid synthesis and metabolism

Peripheral nerve damage (nutritional melalgia or "burning foot syndrome")



Coenzyme in carboxylation reactions in gluconeogenesis and fatty acid synthesis; role in regulation of cell cycle

Impaired fat and carbohydrate metabolism, dermatitis


Ascorbic acid

Coenzyme in hydroxylation of proline and lysine in collagen synthesis; antioxidant; enhances absorption of iron

Scurvy—impaired wound healing, loss of dental cement, subcutaneous hemorrhage



Water Soluble Vitamins

  1. Ascorbic Acid (Vitamin C)

    Sourcescitrus fruits, strawberries and raw or minimally cooked vegetable.

  2. Functions

    1. Vitamin C is required for hydroxylation of proline & lysine residues during the biosynthesis of collagen.
    2. required in synthesis of norepinephrine & epinephrine
    3. helps in iron absorption
    4. Vitamin C is a water-soluble antioxidant that maintains vitamins E and many metal cofactors in the reduced state.
3.  Deficiency – Scurvy

Thiamine (Vitamin B1)

Thiamine contains– a) Pyrimidine; b) thiazole ring

Biological active form — TPP (thiamine pyrophosphate)

TPP act as coenzyme for following enzymes
  1. Pyruvate dehydrogenase complex
  2. α-ketoglutarate dehydrogenase complex
  3. Transketolase
  4.  Tryptophan pyrrolase
  5. Branched chain α-keto acid decarboxylase

Deficiency Manifestations:

Deficiency of B1 leads to disturbance in carbohydrate metabolism and decreased transketolase activity, particularly in erythrocytes and leukocytes and clinical deficiency leads to cardiovascular and neurologic decision.
  • dry beriberi – Peripheral neuropathy, fatigue & impaired capacity to work.
  • wet beriberi – In addition to neurologic manifestation, cardiovascular symptoms are more apparent. Including heart enlargement & tachycardia.
  • Wernicke-Korsakoff syndrome– develops in most acute deficiency is seen primarily in alcoholics.

Riboflavin (Vitamin B2)

Biologically active form:
  1. FMN (Flavin mononucleotide)
  2. FAD (Flavin adenine dinucleotide)
  3. Functions : the coenzyme FAD & FMN are required by several oxidative enzymes. e.g.
    1. FMN : Cytochrome c-reductase, L-amino acid oxidase
    2. FAD: Xanthine oxidase, D-amino and oxidase.
    3. Deficiency – of Vitamin B2 causes ariboflavinosis characterized by vascularization of cornea, lesion of lips, mouth skin & genitalia specially, angular stomatitis, cheilosis, glossitis & seborrheic dermatitis.


  1. Niacin is formed in humans during the catabolism of tryptophan. 60 mg of tryptophan can give rise to 1 mg of niacin.
  2. Metabolism & Function – Niacin is precursor for biosynthesis of NAD & NADP+ which are essential cofactor involved in variety of biological oxidation – reductions reactions.
  3. NAD
    Alcohol dehydrogenase (Ethanol –→ Acetaldehyde)
    Lactate dehydrogenase (Pyruvic acid  Lactic acid)
    Malate dehydrogenase (Malate oxaloacetate)
    Pyruvate dehydrogenase complex (Pyruvate Acetyl CoA)
    α-ketoglutarate dehydrogenase complex (α-Ketoglutarate –→ Succinyl CoA)
  4.  NADP+
  5. Glucose – 6– Phosphate dehydrogenase (G6P →  6-Phosphogluconate) 
  6. Glutathione reductase
  7. Either NAD+ Or NADP+

  8. Glutamate dehydrogenase
  9. Isocitrate dehydrogenase
  10. Deficiency – Pellagra;  Clinical Symptoms Includes

    1. Dermatitis
    2. Diarrhea
    3. Dementia

Pyridoxine (Vitamin B6)

Pyridoxine & closely related compounds (i.e., pyridoxamine, pyridoxal) can function as B6.  However, these compounds are converted by phosphorylation to biologically active cofactor Pyridoxal Phosphate.

A wide range of reactions in which PLP act as cofactor are:
  1. Transamination
  2. Decarboxylations
  3. Aldol cleavages
  4. Racemizations
  5. Deaminations
  6. PLP is also a cofactor glycogen phosphorylase
  7. Coenzyme for kynureninase
  8. Coenzyme in the biosynthesis of arachidonic acid & Linoleic acid.
Deficiency – usually occur as a result of interaction with ATT drug isoniazid, clinical symptoms include

a. Lesions of skin & mucosa

b. Sideroblastic Anaemia

c.   Neuronal dysfunction 3

Pantothenic Acid

  1. Function– Pantothenic acid is a precursor in the biosynthesis of coenzyme A (CoA)
  2. Deficiency– Deficiency in humans is practically unknown

Biotin (AIIMS May 08)

  1. Biotin is synthesized by intestinal micro-organism in sufficient quantity that a dietary source is normally not necessary.
  2. Function – Biotin act as coenzyme in carboxylation reactions for the enzymes carboxylases, where it is carrier of Carbon dioxide.
  3. Conversion of acetyl coA to malonyl COA catalyzed by enzyme acetyl – CoA carboxylase.
  4. Conversion of propionyl CoA to methyl malonyl CoA catalyzed by propionyl CoA carboxylase.
  5. Conversion of pyruvic acid to oxaloacetate by pyruvate carboxylase
Deficiency – Biotin deficiency occurs usually because of large amount of avidin, protein present in raw egg.

Folic Acid

Folic acid is consist of a pteridine ring, P-aminobenzoate and glutamic acid.
Biological active form – is Tetrahydrofolate– F. H4 which is produced by two step reduction of folate by dihydrofolate reductase.

Folic Acid

  1. Folinic acid – this is an active form of folic acid – a formyl derivative. It is reduced tetrahydrofolate (F.H4) with a formyl group on position 5.
  2. Metabolic role – (“One Carbon” metabolism)
    1. The folic acid coenzymes are specifically concerned with metabolic reactions involving transfer & utilization of one carbon moiety.
    2. One carbon moiety may be either methyl (–CH3), formyl (–CHO), formate (HCOO–), formimino group (–CH=NH) or hydroxymethyl – (CH2 OH).
         i.   Folate is necessary for proper purine nucleotide and deoxythymidylate synthesis.
Clinical symptoms of folic acid deficiency includes megaloblastosis of bone marrow (megaloblastic anemia). 
FIGLU test – Used to Detect Folate Deficiency
In the metabolism of amino acid Histidine, these is folic acid dependent step at point where formiminoglutamic acid is converted to glutamic acid. In folic acid deficient patients, this reaction cannot take place, as a result “FIGLU” accumulates in blood & excreted in urine.
So, “FIGLU” excretion in urine is an index of Folate deficiency. FIGLU is also excreted during Histidine overload.

Vitamin B12 (Cyanocobalamine)

  1. Cobalamin is composed in part of a corrin ring with an atom of cobalt present at its active site.
  2. A cyanide group is coordinately bound to cobalt atom, then it is called as cyanocobalamin.
  3. Two active cofactor forms of vitamin are methylcobalamin and 5-deoxyadenosylcobalamins.
  4. Vitamin B12 is absorbed in ileum as a complex with intrinsic factor, a glycoprotein formed in gastric mucosa.
  5. Vitamin is transported in serum bound to globulin & converted to methylcobalamin and 5-deoxyadenocylcobalamin in liver, bone marrow cells and reticulocytes.
  1. Methyl malonyl COA to succinyl COA by enzyme methylmalonyl CoA mutase.
  1. Methyl Malonic aciduria is sensitive index for B12 deficiency
    1. Homocysteine methyltransferase (HMT) which catalyzes the methylation of Homocysteine to methionine requires methylcobalamin as its cofactor.
    2. Conversion of Ribonucleotides to deoxy-ribonucleotides.       

  1. Deficiency – A long term strict vegetarian diet leads to vitamin B12 Deficiency
  2. Pernicious Anemia is consequence of vitamin B12 deficiency.
    It is due to absence of intrinsic factor and its consequences include macrocytic anaemia, megaloblastoses of bone marrow, degeneration of axis cylinders of spinal cord neurons.

Fat Soluble Vitamins

  1. Vitamin A
    Vitamin A has 3 important forms retinal, retinol & retinoic acid. All the three compounds contain a common structural unit called trimethyl cyclohexanol ring & all trans configurate polyene chain with four double bonds.

Storage form: Retinal is esterified with palmitate & transported to liver, where 90% of body vitamin A is stored. Thus ester form is a storage form.

Function of vitamin A in Vision
  1. In the retina, retinaldehyde functions as the prosthetic group of the light-sensitive opsin proteins, forming rhodopsin (in rods) and iodopsin (in cones). Any one cone cell contains only one type of opsin, and is sensitive to only one color.
  2. In the pigment epithelium of the retina, all-trans-retinol is isomerized to 11-cis-retinol and oxidized to 11-cis-retinaldehyde.
  3. This reacts with a lysine residue in opsin, forming the holo-protein rhodopsin. The absorption of light by rhodopsin causes isomerization of the retinaldehyde from 11-cis to all-trans, and a conformational change in opsin.
  4. This results in the release of retinaldehyde from the protein, and the initiation of a nerve impulse. The formation of the initial excited form of rhodopsin, bathorhodopsin, occurs within picoseconds of illumination.
  5. There is then a series of conformational changes leading to the formation of metarhodopsin II, which initiates a guanine nucleotide amplification cascade and then a nerve impulse.
  6. The final step is hydrolysis to release all-trans-retinaldehyde and opsin. The key to initiation of the visual cycle is the availability of 11-cis-retinaldehyde, and hence vitamin A.
  7. In deficiency, both the time taken to adapt to darkness and the ability to see in poor light are impaired.
Functions: Different Forms Are Involved In Different Functions Like
Retinal:  Visual Functions
Retinol & Retinoic Acid : Steroid hormone functions.

  1. Defect in vision progressing from Night blindness to total blindness
  2. Skin lesions e.g. follicular hyperkeratosis
  3. Gonadal dysfunction is males & miscarriage in females.
  1. Vitamin D:  Also Known as Prohormone
  1. Ergocalciferol (Vitamin D2)
  2. cholecalciferol (Vitamin D3 )

Biological active form of Vitamin D is Calcitriol

  1. Vitamin D2 or D3 binds its specific proteins & transported to liver and undergoes hydroxylation at 25 position to form 25-OH cholecalciferol. This reaction requires Mg+2, NADPH and molecular O2.
  2. 25-OH cholecalciferol is the major storage form of vitamin D in liver. This is hydroxylated at C1 to form Calcitriol.

Mode of action of calcitriol
Calcitriol acts in similar way as steroid hormone receptor.
Calcitriol receptor complex binds to chromatin in the nucleus stimulating transcription & formation of mRNA that codes for calcium binding proteins. The increased synthesis of calcium binding proteins helps in absorption and reabsorption of calcium in intestine & kidney.
  1. Functions:  Vitamin D participates in regulation of calcium metabolism
  1. Vitamin K

1.  All Vitamin K Are Napthoquinere Derivativesa.  
  1. Vitamin K1 or Phylloquinone
  2. Vitamin K2 or farnoquinone
  3. Vitamin K3 or Menadione
Vitamin K1 and K2 are two naturally occurring forms of vitamin K and vitamin K3 is its synthetic analogue.

2.  Functions of Vitamin K

  1. Role in Blood coagulation
  2. Role in Oxidative phosphorylation

Test Your Skills Now!
Take a Quiz now
Reviewer Name