This document discusses the vitamins B1 (thiamine), B2 (riboflavin), B3 (niacin), and biotin. It describes their structures, biological roles as coenzymes in energy production and metabolic pathways, and deficiencies that can result from inadequate intake. Thiamine deficiency causes beriberi, while riboflavin deficiency causes inflammation of lips and eyes. Niacin deficiency results in pellagra with skin, digestive, and neurological symptoms. Biotin is required for fatty acid synthesis and the citric acid cycle.

1. Vitamins B1, B2, B3, biotin –
energy-releasing vitamins

3. Active form of Thymine (Thymine
pyrophosphate- TPP)
N
N
H3C
NH2
CH2
S
N
CH3
CH2 CH2O PP
reactive carbon atom
pyrimidine thiazole ring
pyrophosphate

5. TPP is required for energy releasing
reactions such as:
 Oxidative decarboxylation of α-ketoacids:
 E.g. Co-enzyme for pyruvate
dehydrogenase (PDH)
COO
C O
CH3
CoA-SH
SCoA
C O
CH3
+ CO2
NAD+
NADH
TPP
PDH
Pyruvate Acetyl CoA
E.T.C.
(3 ATP)

6. Metabolism of branching amino acids -
Valine:
CH3 CH
CH3
H
C
NH2
COO CH3 CH
CH3
C
O
COO
ketoisovaleric acid
CO2
KDH
(TPP)
NADH
NAD+
CH3 CH
CH3
C
O
SCoA
isobutyryl CoA
succinyl CoA
TCA

7. Role in the transmission of nerve
impulse
 TPP acts as a
phosphate donor for
phosphorylation of
the nerve membrane
sodium transport
channel.

8. THIAMINE DEFICIENCY
 Most dietary deficiency of
thiamine is the result of:
 (i) poor dietary intake
 (ii) diet high in
carbohydrates only
 (iii) alcoholism
 (iv) cancer, chronic illness
 tea, coffee, certain
seafoods may contain
thiaminases that
destroyed the vitamin and
lead to deficiency.

9. Beriberi
 “Beriberi” a neurological disorders, that
was endemic in the polish-rice eating
countries.

10. Types of “beriberi”
Dry Wet
Infantile
Adult Adult In first year
of life
Polyneuritis
(damage of peripheral
nerves)
Cardiac failure
& edema
In late stage,
muscular atrophy results.
May become paralysis
Cardiovascullar
problems

11. Wernike-Karsakoff syndrome:
 Seen primary in association with
chronic alcoholism and is due to
dietary insufficiency or impaired
intestinal absorption of vitamin
B1.
 Characterized by apathy, loss of
memory and rhythmical and fro
movements of eye balls.

14. It forms two biological coenzymes:
 Flavin Mononucleotide (FMN)
 Flavin Adenine Dinucleotide (FAD).
– FMN and FAD help in the oxidation-reduction
reactions.
– FMN and FAD are the coenzymes of enzymes
which are involved in the synthesis of ATP in
mitochondria (TCA cycle, ETC).

15. DEFICIENCY OF VITAMIN B2
 Inflammation of lips,
stomatitis.
 Inflammation and
vascularization of
cornea, photophobia
(intolerance of light),
cataract formation.

17. Structure
N
C
O
OH
N
C
O
NH2
nicotinic acid
nicotinamide
(coenzyme of NAD+
,
NADP+
)
R

19. Deficiency of Niacin causes Pellagra.
 Pellagra is a disease involving the skin,
gastrointestinal tract and central nervous
system.
 Symptoms of pellagra 3 Ds:
 Dermatitis (lesion of skin of face, neck, thick and
scaly skin).
 Dementia (headache, depression, forgetfulness,
insomnia (loss of sleep), anxiety.
 Diarrhea
 Death (4th D) is not treated.

20. CLINICAL USES OF NIACIN
 It is used in the
treatment of
hyperlipidemia
 Niacin strongly
inhibits lipolysis in
adipose tissues
 decrease lipogenesis
in the liver

21. Biotin
 SOURCES:
 Present in almost all
foods particularly in
liver, milk, egg yolk,
chocolate
 Intestinal bacteria
also supply biotin in
large proportion.

22. Structure

23. Biological role
– Biotin is a coenzyme of carboxylase.
– It helps in the incorporation of carbon dioxide
(CO2) – CO2-“fixation” reaction.
COO
C O
CH3
CO2 COO
C O
CH2
COO
biotin
pyruvate
oxaloacetate
(TCA cycle
energy providing)

24. Biotin involves in the following
reactions:
 Purine synthesis
 Fatty acids synthesis
 Propionate convertion to succinate (TCA
cycle)

25. DEFICIENCY:
– The deficiency of biotin
may result from:
 The destruction of intestinal
bacteria by sulfonamide
drugs.
 The inadequate intake of egg
white which contains the
protein avidin (interfere
absorption of biotin) in
association with diarrhea in
case of infants.