Vitamin A has roles in normal reproduction, the visual cycle, glycoprotein synthesis, mitochondrial membrane function, and as an antioxidant. Vitamin D promotes calcium and phosphate absorption and regulates calcium levels. It also promotes bone mineralization, growth, and dental health. Vitamin E is a potent antioxidant that protects cell membranes and is involved in reproduction, muscle integrity, and heme synthesis. Vitamin K is needed for blood clotting factor synthesis and carboxylation. Vitamin C acts as a reducing agent and cofactor for hydroxylases involved in collagen synthesis, carnitine formation, and adrenal function. It also aids iron absorption and tetrahydrofolate formation.

2. BIOLOGICAL ROLE OF VITAMIN-A
1. Retinol and retinoic acid have role in
normal reproduction
2. Retinal has a role in visual cycle
3. Retinoic acid has a role in glycoprotein
synthesis
4. Roll in MPS synthesis
5. Vitamin-A is needed for mitochondrial
membrane function

3. 6. Anti cancer role: β-carotene is an
antioxidant and trap peroxy free radicals
in tissues at low partial pressure of O 2
7. Role in reproduction
8. Bone and teeth formation is slow

4. BIOCHEMICAL ACTIONS OF
CHOLECALCIFEROL
1. Vitamin-D promotes absorption of Ca ++ and
P by the intestine. It stimulates the
synthesis of a specific Ca++ binding protein
by intestinal epithelium.
2. Vitamin-D induces the synthesis of specific
Ca++ binding protein in bones
3. Vitamin-D regulates the Ca++ level by
reabsorbing Ca++ through the kidney

5. 4. Vitamin-D promotes mineralization of
bones through deposition of Ca++ and P in
growing bones.
5. Vitamin-D increases the reabsorption of
PO4 through renal tubules.
6. Vitamin-D acts as coenzyme for alkaline
phosphatase
7. Vitamin-D is responsible for enameling of
the teeth. Its deficiency leads to irregular
and rough teeth

6. 8. Vitamin-D promotes growth in general and
is essential for normal health. BMR is
decreased in vitamin-D deficiency. The
deficiency of vitamin-D leads to the
repeated attacks of respiratory diseases.

7. BIOCHEMICAL ACTIONS OF
VITAMIN-E
1. Antioxidant role: Vitamin-E is the most
potent natural antioxidant.
2. Removal of Free radicals: Vitamin-E
removes free radicals, prevents their
peroxidative effects on unsaturated lipids
of membrane and thus maintains integrity
of membranes.

8. 3. Protective role: i. Vitamin-E prevents
massive hepatic necrosis produced on diet
deficient in sulphur containing aminoacids.
4. Role in reproduction: It is required for
normal reproduction, muscle integrity and
for resistance of erythrocytes to hemolysis.
5. Role in Heme Synthesis: Vitamin-E also
takes part in the synthesis of heme.
Vitamin-E induces enzymes ALA-synthase
and ALA-dehydratase.

9. 6. A derivative of vitamin-E is said to be
necessary for the synthesis of CoQ which
is the component of mitochondrial electron
transport chain.

10. BIOLOGICAL ACTIONS OF VITAMIN-K
1. Vitamin-K is needed for formation of
proconvertin: It is needed for the formation
of prothrombin. Deficiency of vitamin K
decreases proconvertin level in blood.
2. Vitamin-K modifies prothrombin: Vitamin-K
is a coenzyme in modification of
prothrombin to thrombin.

11. 3. Vitamin-K modifies other clotting factors
also: Vitamin K is needed for maintenance
of normal levels of blood clotting factors II,
VII, IX and X. All these factors are
synthesized in the liver in their zymogen
forms. Their conversion to biologically
active forms depends upon vitamin K. The
activation involves carboxylation of
glutamyl residues in the molecules of
these factors (including prothrombin also)
to form dicarboxylic glutamyl residue.

12. 4. Vitamin-K is needed for carboxylation of
glutamyl residue of Ca++ binding transport
between the flavin coenzyme and the
cytochrome system.

13. FACTORS CAUSING VITAMIN-K
DEFICIENCY:
• Surgical removal of intestine:
• Liquid paraffin:
• Antibiotic therapy for a long time:
• Vitamin-K antagonists: Heparin and warfarin

14. BIOCHEMICAL FUNCTIONS:
THIAMINE
• TPP [cocaroxylase] being an essential
part of the decarboxylating
dehydrogenases acts as a cofactor in
many important reactions in carbohydrate
metabolism i.e., dehydrogenase [PDH]
complex and α-ketoglutarate
dehydrogenase [αKGDH] complex
i. Oxidative Decarboxylation of α-ketoacids

15. ii. Conversion of α-Ketoglutarate to succinyl-
SCoA
iii. TPP acts as coenzyme in reactions
catalyzed by transketolase
iv. Tryptophan metabolism:
Tryptophan pyrrolase
Tryptophan N-formylkynurenine
O2

16. v. TPP is a coenzyme for mitochondrial
branched chain α-ketoacid
dehydrogenases [decarboxylases] which
oxidatively decarboxylate α-ketoacids
formed in the catabolsim of valine, leucine
and isoleucline.
vi. In the nervous system: TPP is a cofactor
for the synthesis of acetylcholine.
vii. TPP also acts as a coenzyme [co-
carboxylase] for pyruvate carboxylase in
yeast for non-oxidative decaroxylation of
pyruvate to acetaldehyde.

17. BIOCHEMICAL FUNCTIONS OF
RIBOFLAVIN:
A- Biochemical role of FMN as a coenzyme
1. FMN as a part of redox potential
2. FMN is a coenzyme for L-amino acid
oxidases:
3. FMN being a part of Cut. C reductase
4. FMN also accepts 2H+ from NADH+H+
5. FMN is a coenzyme for Warburg’s yellow
enzyme [a component of respiratory chain]

18. B- FAD is a coenzyme for the following
enzyme:
Like FMN, FAD is also is a part of
mitochondrial respiratory chain
1. D-aminoacid oxidases: The enzymes
catalyze reaction similar to L-aminoacid
oxidases but with FAD as coenzyme.
2. Aldehyde oxidase
3. Acyl-CoA dehydrogenase of the β
oxidation of fatty acids

19. 4. Succinate dehydrogenase, an enzyme of
citric acids cycle and converts succinate
to fumarate in mitochondria
5. Xanthine oxidase present in milk, small
intestine, kidney and liver has Mo as its
activator ion converts urine bases to uric
acid
6. Glucose oxidase prepared from fungi
7. Glycine oxidase which oxidatively
deaminates glycine to glyoxylic acid and
ammonia

20. NIACIN
NAD+ and NADH are coenzymes of niacin:
A- NAD+ containing dehydrogenases are:
1. Isocitrate dehydrogenase of mitochondrial
origin.
2. Alcohol dehydrogenase
3. Lactate dehydrogenase
4. Malate dehydrogenase of citric acid cycle.
Malate Oxaloacetate

21. 5. Glyceraldehyde-3-P dehyrogenase of
glycolysis
6. Pyrurate dehydrogenase complex
7. α-ketoglutarate dehydrogenase of citric
acid cycle.
8. β-hydroxy fatty acyl-coA dehydrogenase of
β-oxidation of fatty acids

22. B- NADP+ containing dehydrogenases are:
1. Isocitrate dehydrogenase of extra
mitochondrial origin.
2. Glucose-6-phosphate dehydrogenase of
HMP-shunt
3. β-ketoacyl reductase in the fatty acid
synthesis
4. HMG-CoA reductase in cholesterol
synthesis
HMG-CoA → Mevalonate

23. 5. Enoyl reductase of fatty acid synthase
complex

24. BIOCHEMICAL ACTIONS:
PANTO THENIC ACID
1. Formation of active acetate [Acetyl-CoA]:
CoA-SH
2. Formation of acetyl-ACP and malonyl-
ACP
3. Role in oxidation of fatty acids, formation
of fats and phospholipids:

25. 4. Heme Synthesis: Ative succinate
[succinyl-CoA] is product of oxidative
decarboxylation of α-oxoglutarate in TCA
cycle. Succinyl-CoA and glycine is needed
for the synthesis of heme.

26. BIOCHEMICAL FUNTIONS OF
PYRIDOXINE:
1. As co-transaminase: It acts as a
coenzyme in transamination reactions.
GOT [AST] and GPT [ALT] are
transaminases which need PLP as
coenzyme for their actions
2. As co-decarboxylase: It also functions as
a coenzyme in non-oxidative
decarboxylation of some aminoacids or
their derivatives.

27. Tyrosine Tyramine + CO2
Histidine Histamine + CO2
3. As Ala-synthase: in the synthesis of δ-
aminolevulinic acid which is an
intermediate in heme synthesis
4. As coenzyme in the conversion of
tryptophan to niacin.
5. Interconversion of glycine and serine by
hydroxymethyl transferase.

28. 6. In transulphuration reactions, where
transfer of-SH group takes place, B 6 is
needed.
7. In synthesis of sphingosine
8. Intramitochondrial fatty acid synthesis
9. Intestinal absorption of aminoacids
10. Transport of K+. B6 is reported to promote
transport of K+ across the membrane.

29. 11. Synthesis of CoA-SH from pantothenic
acid needs B6. in B6 deficiency CoA level of
the liver is decreased.
12. B6 acts as a coenzyme for glycine
Synthase.

30. BIOCHEMICAL FUNCTIONS OF
BIOTIN
Biotin is a prosthetic group of some
enzymes catalyzing CO2 transfer or CO2
fixation reactions.
1. Formation of malonyl-CoA from acety-
CoA and CO2
2. Pyruvate carboxylase Reaction: Here
pyruvate forms oxaloacetate.

31. 3. Formation of carbamoyl-PO4: NH3, CO2
and ATP requires biotin to form
carbamyl-PO4 in presence of carbamyl-
PO4 synthetase.
4. Formation of β-methylglutaconyl-CoA
from β-methylcrotonyl-CoA. It is an
intermediate reaction in leucine
metabolism

32. 5. Biotin influences other enzyme systems
e.g. succinate dehydrogenase,
decarboxylase and aminoacid
deaminases. Here CO2 is used for the
formation of aspartic acid, serine and
threonine.
6. Propionyl-CoA carboxylase reaction
requires biotin
ATP
Propionyl-CoA+CO2 → Methylmalonyl-CoA
ADP+Pi

33. COENZYME FORMS OF FOLIC
ACID:
1. Tetrahydrofolic acid, FH4:
2. Folinic acid:
3. Rhizopterin:

34. METABOLIC ROLE (ONE
CARBON METABOLISM):
FH4 is the coenzyme form of folic acid and it
acts as coenzyme in transfer and
utilization of one carbon moiety [C1]
One Carbon Donor and Acceptor
Compounds:

35. One carbon donor group One carbon acceptor group
Formimino group of N-formyl methionine of
formimino glu [from his]. transfer-RNA.
Methyl group of methionine. Glycine to form serine.
Methyl group of methionine. Glycine to form serine.
Methyl group of thymine. Uracil to form thymine.
β-carbon of serine. Ethanolamine to form choline.
Gly, trp, ALA and acetone, Positions 2 and 8 of purin ring.
Histidine synthesis.

36. FOLATE ANTAGONISTS:
1. SULFONAMIDES
2. TRIMETHOPRIM:
3. PYRIMETHAMINE:
4. AMINOPTERIN AND AMETHOPTERIN:

37. BIOCHEMICAL FUNCTIONS OF
B12
1. Methylmalonyl-CoA-isomerase: It
catalyzes the reaction using B12 as a
coenzyme
Methylmalonyl-CoA → succinyl-CoA
2. Methionine synthase or homocysteine
methyl transferase requires B12 as
coenzyme:

38. 3. Conversion of Ribonucleotide to
deoxyribonucleotide also needs B12. It is
important in the synthesis of DNA hence
deficiency of B12 leads to the defective
synthesis of DNA.
4. Role as Hemopoietic Factor: Like folic acid,
vitamin B12 is also concerned with
hemopoiesis and is needed for maturation
of RBCs.

39. 5. Abnormal Homocysteine Level: In
vitamin B12 deficiency, Homocysteine
Conversion to methionine a block so that
homocysteine is accumulated, leading to
homocystienuria. Homocysteine level in
blood is related with myocardial
infarction. So1, B12 is protective against
cardiac disease.

40. Demyelination and Neurological Deficits: In
B12 deficiency, methylation of
phosphatidyl ethanolamine to phosphatidyl
choline is not adequate. This leads to
deficient formation
Of myelin sheaths of nerves, demyelination
and neurological lesions.

41. CAUSES OF B12 DEFICIENCY:
1. Nutritional B12 deficiency.
2. Decrease in absorption due to non-
availability of absorptive sufface caused
by gastrectomy, resection of ileum, blind
loop syndrome.
3. Elderly people are unable to absorb B 12

42. 4. Addisonian anemia is pernicious [fatal]
without any remedy. It is manifested in
persons 40 years of age. It is an
autoimmune disease and antibodies are
formed against IF. The deficiency of IF
leads to defective absorption of B12.
5. Atrophy of gastric epithelium: It leads to
decreased IF and decreased absorption
of B12.

43. 6. Drugs: Some drugs interfere with
absorption of B12. These are phenphormin,
cholchicine, neomycine, ethanol and KCl.
7. Increased requirement of B12 in pregnancy
is common cause for vitamin B12
deficiency.

44. BIOCHEMICAL FUNCTIONS OF
ASCORBIC ACID:
1. Vitamin C acts as a reducing agent:
2. The oxidation of p-hydroxphenyl
pyruvate to homogentisate in the
metabolism of tyrosine needs the
presence of vitamin V and Cu+2
3. Role in iron absorption: Ascorbic acid
present in food reduces the inorganic Fe +
++
(ic) to Fe++ (ous) form.

45. 4. Vitamin-C acts as a coenzyme for
hydroxylases. Hydroxylation reactions
are involved in the synthesis of collagen
and other compounds:
5. Formation of carnitine in liver by
hydroxylation of γ-butyrobetaine involves
vitamin-C, α-ketoglutarate, Fe++ and a
dioxygenase.
6. Vitamin-C required for the normal
function of adrenal cortex.

46. 7. The formation of FH4 from folate needs
vitamin-C. Tetrahydrofolate [FH4] is a
coenzyme from of folate.
8. Ascorbic acid is necessary for the
formation of tissue ferritin.
9. Vitamin C is needed for the functional
activity of fibroblast, osteoblast, and
consequently for the synthesis of MPS of
connective tissues, osteoid tissues,
dentine tissues and intracellular
substance involved in the cementing of
capillaries.