Download Vitamin `C

COURSE TITLE: BIOCHEMISTRY 1
COURSE CODE: BCHT 201
PLACEMENT/YEAR/LEVEL: 2nd Year/Level 4, 1st Semester
M.F.Ullah, Ph.D
Showket H.Bhat, PhD
VITAMINS
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History of vitamins :
The story of vitamin dates back to 18th
century.
In 1912, Sir H.G. Hopkins first identified
Vitamins in MILK and named it as Accessory
factors.
Funk named the accessory factors as Vitamins
(Vital amines).
What are vitamins: Basic definition
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Vitamins are micronutrients, which are essential
for growth and metabolism.
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Non-caloric organic nutrients (Do not provide energy)
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Needed in very small amounts but essential so must
be supplied through diet except those which are not
essential dietary vitamins as can be synthesized by the
intestinal bacteria (vitamin K) or by sunlight (vitamin D)
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Facilitators – Participate in the physiologigal processes
facilitating biochemical pathways for digestion,
absorption, metabolism, growth etc.
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Some appear in food as precursors called as
Classification
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Vitamins are classified into two types – based
on their solubility .

Water soluble vitamins & Fat soluble vitamins.
Water soluble Vitamins - Vitamin ‘B’ complex and
Vitamin ‘C’
Fat soluble vitamins - Vitamin A, Vitamin D,
Vitamin E and Vitamin K
Water soluble vitamins
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Water soluble vitamins
◦ Found in vegetables, fruit & grains, meat.
◦ Absorbed directly into the blood stream
◦ Not stored in the body and toxicity is rare.
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Vitamin B Complex is a group of water soluble
vitamins.
It contains –
a) Thiamine – B1
b) Riboflavin – B2
c) Niacin
- B3
d) Pyridoxine – B6
e) Cyanocobalamin – B12
f) Folic acid
g) Pantothenic acid
h) Biotin
Mode of action – Vitamins of B complex series act as constituents of
coenzymes that are necessary for the proper activity of enzymes.
Coenzymes are small organic molecules that link to enzymes and whose
presence is essential to the activity of those enzymes. They bind to the
active site of the enzyme and participate in catalysis without being
transformed (changed) at the end of the reaction.
coenzymes often function as intermediate carriers of electrons, specific
atoms or functional groups that are transferred in the overall reaction.
VITAMINS AND COENZYMES
Vitamin
Coenzyme
Reaction type
B 1 (Thiamine)
TPP
Oxidative decarboxylation
B 2 (Riboflavin)
FAD
Oxidation/Reduction
(Pantothenate)
CoA - Coenzyme A
Acyl group transfer
B 6 (Pyridoxine)
PLP
Niacin( B3)
5-deoxyadenosyl
cobalamin
NAD +
Transfer of groups to and
from amino acids
Intramolecular
rearrangements
Oxidation/Reduction
Folic acid
Tetrahydrofolate
One carbon group transfer
Biotin
Biotin
Carboxylation
B
12 (Cobalamin)
Compounds
Without the coenzyme, compounds A
and B don’t respond to the enzyme.
A
B
Active site
Enzyme
With the coenzyme in place,
compounds A and B are attracted to
the active site on the enzyme, and they
react.
The reaction is completed with the
formation of a new product. In this case,
the product is AB.
The product AB is released.
A
B
Vitamin
Coenzyme
Enzyme
A B
Enzyme
A B
New product
Enzyme
Brain and
other tissues
metabolize
carbohydrates.
Muscles and
other tissues
metabolize
protein.
Thiamine pyrophosphate((TPP)
Flavin adenine dinucleotide (FAD)
Nicotinamide adenine dinucleotide
(NAD+)
Flavin mononucleotide (FMN)
Pyridoxal phosphate (PLP)
Tetrahydrofolic acid (THF) Liver and other
tissues
Coenzyme A (CoA)
metabolize fat.
Bone tissues
make new
blood cells.
Digestive
tract
lining
replaces
its cells.
Thiamine or thiamin or vitamin B1 , named as the "thio-vitamine" ("sulfur-containing
vitamin") is a water-soluble vitamin of the B complex.
Its phosphate derivatives are involved in many cellular processes. The best-characterized
form is thiamine pyrophosphate(TPP), a coenzyme in the catabolism of sugars and amino
acids.
Thiamine is used in the biosynthesis of the neurotransmitter acetylcholine and gammaaminobutyric acid (GABA). In yeast, TPP is also required in the first step of alcoholic
fermentation.
All living organisms use thiamine in their biochemistry, but it is synthesized only
in bacteria,fungi, and plants. Animals must obtain it from their diet, and thus, for them, it
is an essential nutrient.
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Deficiency disease - Beri-Beri.
In this disease, the calf muscles become tender, vomiting, tremors, convulsions, loss
of appetite are seen.
Sources: Cereals like wheat, oil seeds like groundnut, milk, meat, fish.
Riboflavin, also known as vitamin B2 is an easily absorbed
colored micronutrient
It is the central component of the cofactors FAD and FMN, and is therefore
required by all flavoproteins.
The
name
"riboflavin"
comes
from
"ribose"
(the
sugar
whose reduced form, ribitol, forms part of its structure) and "flavin", the
ring-moiety which imparts the yellow color to the oxidized molecule (from
Latin flavus, "yellow").
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Functions: Riboflavin is essential for oxidation reduction reactions
in the cell. vitamin B2 is required for a wide variety of cellular
processes. It plays a key role in energy metabolism, and for
the metabolism of fats, ketone bodies, carbohydrates,
and proteins.
Sources: It is present in milk, eggs, liver, kidney and green leafy
vegetables.
Deficiency disorders: Deficiency of riboflavin result in Glossitis
Mouth cracks at corners. Photophobia, scaly skin and watering of
eyes are some of the symptoms.
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Niacin is one of the ‘B’ Complex Vitamins. It is also known as
Vitamin B3.
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Functions:
Niacin
is
a
precursor
to
NAD+/NADH
and
NADP+/NADPH,
which
play
essential metabolic roles in living cells.
Niacin is involved in both DNA repair, and the production of steroid
hormones in the adrenal gland.
Niacin has been used to increase levels of HDL in the blood and has
been found to modestly decrease the risk of cardiovascular events in a
number of controlled human trials.
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Sources: It is present in kidney, liver, meat, poultry fish, legumes and
groundnuts.
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Deficiency disorders: Deficiency of niacin in diet result a disease
called Pellagra. The symptoms of pellagra are diarrhea, dementia (loss
of memory) patches on the body when exposed to sunlight .
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Pyridoxine is otherwise called Vitamin-B6.
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Functions: Pyridoxine plays an important role in the metabolism of
amino acids as constituent of cofactor pyridoxal phopshate (PLP)
for enzyme amino tranferasesin transamination reactions.
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Sources: It is present in milk, liver, meat, egg yolk, fish, cereals,
legumes and
vegetables.
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Deficiency disorders: Deficiency lead to hyper irritability, anaemia,
nausea and in children it leads to convulsions.
Folic Acid
 Sources: It is present in liver, meat, eggs, milk,
fruits, cereals, and leafy vegetables over cooking
of food destroys the folic acid
 Functions :
 Precursor of coenzyme tetrahydrofolate (THF)
required in nucleic acid biosynthesis reactions.
 Folic acid is required for the synthesis of nucleic
acids (DNA and RNA).
 It is also required for the development of blood
cells in the bone marrow.
 Deficiency Symptoms: Its deficiency causes
anemia, diarrhoea and decrease in the number of
leucocytes.
 Cell division in tissues such as intestinal mucosa
is affected in folic acid deficiency.
Cyano cobalamin: It is also known as vitamin B12
 Functions:
It plays an important role in the metabolism of protein.
Sources :
Bacteria present in the intestine synthesize this vitamin and
supply to our body.
 Liver is the main site of storage of vitamin B12
 Deficiency diseases :
Deficiency of this vitamin causes pernicious anemia (Pernicious
anemia is a decrease in red blood cells that occurs when the
intestines cannot properly absorb vitamin B12 due to loss of
pareital cells which secrete intrinisic factor for B12
absorption).
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It is one of the ‘B’ complex vitamins.
Functions: It is required for the metabolism of
carbohydrates, proteins and fats.
Sources: The sources of pantothenic acid are fresh
vegetables, liver, kidney, yeast, egg yolk, meat, ground
nuts etc.
Deficiency leads to burning sensation in feet
Biotin is one among the ‘B’ complex vitamins.
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Functions: It is required for carboxylation
reactions.
Sources: Biotin is present in pulses, nuts,
vegetables, liver and kidney.
Deficiency disorders: Deficiency leads to
muscle pains, fatigue, disorders in the nervous
system and mental depression.
Vitamin C – It is also called as Ascorbic Acid. Like
vitamin B complex vitamin C is also classified as water
soluble vitamins
Sources: Vitamin C is present in fresh fruits, green leafy vegetables,
tomatoes and germinating pulses.
 Citrus fruit and Indian gooseberry are the richest source of this vitamin.
 Guava is another cheap and rich source of Vitamin C.
 Functions
*Vitamin C plays an important role in tissue oxidation reactions
(anti-oxidant)
*It is required for the formation of collagen which is essential for the
formation of blood vessels, connective tissue, cartilage and dentine of
teeth.
*Vitamin C also helps in the absorption and storage of iron.
* Vitamin C is also required for normal growth, tissue repair, healing of
wounds and fracture of bone.
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Vitamin C deficiency: SCURVY
Scurvy is the nutritional disorder caused due
to the deficiency of Vitamin ‘C’.
The symptoms of this disease are swelling of
gums, bleeding from gums and from the
joints and under the skin.
This disease is preventable by providing the
diet that is rich with Vitamin-‘C’.