Transcript Vitamin A

vitamins
A vitamin is an organic compound required as a
nutrient in tiny amounts by an organism., and
must be obtained from the diet.
Vitamins are required to perform
specific cellular functions.
Vitamins have diverse biochemical
functions.
 Some have hormone-like functions as
regulators of mineral metabolism (e.g., vitamin
D), or
 regulators of cell and tissue growth and
differentiation (e.g., some forms of vitamin A).
 Others function as antioxidants (e.g., vitamin
E and sometimes vitamin C)
 The largest number of vitamins (e.g., B
complex vitamins) function as precursors for
enzyme cofactors, that help enzymes in their
work as catalysts in metabolism
The term vitamin was derived from "vitamine,"
a combination word made up by Polish
scientist Casimir Funk from vital and amine,
meaning amine of life, because it was
suggested in 1912 that the organic
micronutrient food factors that prevent beriberi
and perhaps other similar dietary-deficiency
diseases might be chemical amines.
This proved incorrect for the micronutrient
class, and the word was shortened to vitamin.
Classification of vitamins
Water-soluble vitamins dissolve easily in water •
and, in general, are readily excreted from the
body.
Because they are not readily stored, consistent
daily intake is important. Many types of watersoluble vitamins are synthesized by bacteria.
Fat-soluble vitamins are absorbed through the •
intestinal tract with the help of lipids (fats).
Because they are more likely to accumulate in
the body, they are more likely to lead to
hypervitaminosis than are water-soluble
vitamins
Fat soluble vitamin
Vitamin A (retinol)
Source
Physiological Functions
Deficiency
Overconsumption
Vitamin A: liver,
vitamin A
fortified milk and
dairy products,
butter, whole
milk, cheese, egg
yolk.
Provitamin A:
carrots, leafy
green vegetables,
sweet potatoes,
pumpkins, winter
squash, apricots,
cantaloupe.
Helps to form skin and
mucous membranes and
keep them healthy, thus
increasing resistance to
infections; essential for
night vision; promotes
bones and tooth
development. Beta
carotene is an antioxidant
and may protect against
cancer.
Mild:
night blindness,
diarrhea, intestinal
infections,
impaired vision.
Severe:
inflammation of
eyes,
keratinization of
skin and eyes.
Mild: nausea,
irritability, blurred
vision.
Severe: growth
retardation,
enlargement of
liver and spleen,
loss of hair, bone
pain, increased
pressure in skull,
skin changes
Vitamin D
Source
Physiological Functions
Deficiency
Vitamin Dfortified
dairy
products,
fortified
margarine,
fish oils,
egg yolk.
Synthesize
d by
sunlight
action on
skin..
Promotes hardening of Severe:
bones and teeth,
Rickets
increases the
in children;
absorption of calcium.. osteomalacia in
adults.
Overconsumption
Mild: nausea,
weight loss,
irritability.
Severe: mental
and physical
growth
retardation,
kidney
damage,
movement of
calcium from
bones into soft
tissues.
Fatty fish such as salmon are dietary sources
of vitamin D
Vitamin E
Source
Physiological Functions
Vegetable
oil,
margarine,
butter,
shortening,
green and
leafy
vegetables,
wheat germ,
whole grain
products,
nuts, egg
yolk, liver.
Protects vitamins A
and C and fatty
acids; prevents
damage to cell
membranes.
Antioxidant.
Deficiency
Sensitivity of
erythrocytes
to peroxide,
and the
appearance
of abnormal
cellular
membranes.
Overconsumption
Nontoxic under
normal conditions.
Severe: nausea,
digestive tract
disorders
Vitamin K
Source
Physiological
Functions
Dark green leafy
Helps blood to
vegetables, liver; also clot.
made by bacteria in
the intestine.
Deficiency
Overconsumption
Excessive
bleeding.
Nontoxic under
normal
conditions.
None reported.
Water soluble vitamin
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Folic acid
Cobalamin (vitamin B12)
Ascorbic acid (vitamin C)
Pyridoxine (vitamin B6)
Thiamine (Vitamin B1)
Niacin (vitamin B3)
Riboflavin (vitamin B2)
Biotin
Pantothenic acid
Vitamin C (ascorbic acid)
Common food
sources
Major functions
Deficiency
symptoms
Overconsumption
symptoms
Stability in foods
Citrus fruits,
broccoli,
strawberries,
melon, green
pepper, tomatoes,
dark green
vegetables,
potatoes.
Formation of
collagen (a
component of
tissues), helps hold
them together;
wound healing;
maintaining blood
vessels, bones,
teeth; absorption
of iron, calcium,
folacin; production
of brain hormones,
immune factors;
antioxidant.
A deficiency of
ascorbic acid
result in:
scurvy, a
disease
characterized
by sore, spongy
gums loose teeth
fragile blood
vessels swollen
joints anemia
.
Nontoxic under
normal
conditions;
rebound scurvy
when high doses
discontinued;
diarrhea,
bloating,
cramps;
increased
incidence of
kidney stones
Most unstable
under heat,
drying, storage;
very soluble in
water, leaches
out of some
vegetables
during cooking;
alkalinity
(baking soda)
destroys vitamin
C.
Thiamin (vitamin B1 )
Common food
sources
Pork, liver, whole
grains, enriched
grain products,
peas, meat,
legumes.
Major
functions
Helps release
energy from
foods;
promotes
normal
appetite;
important in
function of
nervous
system.
Deficiency
symptoms
Beriberi is a
neurological
disease.
Beriberi is
characterized by
Dry skin
Irritability
Disorderly
thinking
Progressive
paralysis
.
Overconsumption
symptoms
Stability in foods
None known. Losses depend
on cooking
method,
length,
alkalinity of
cooking
medium;
destroyed by
sulfite used to
treat dried
fruits such as
apricots;
dissolves in
cooking water.
Riboflavin (vitamin B2)
Deficiency
symptoms
Over
consumption
symptoms
Common food
sources
Major functions
Liver, milk, dark
green vegetables,
whole and enriched
grain products, eggs.
Helps release energy Cracks at
None known.
from foods; promotes corners of
good vision, healthy mouth;
dermatitis
Flavin ononucleotide around nose and
(FMN) and flavin
lips; eyes
adenine dinucleotide sensitive to
(FAD) function as
light.
coenzymes for a wide
variety of oxidative
enzymes and remain
bound to the enzymes
during the oxidationreduction reactions.
skin.
Stability in foods
Sensitive to
light;
unstable in
alkaline
solutions
Niacin (nicotinamide, nicotinic acid, vitamin B3)
Common food
sources
Major functions
Deficiency symptoms
Over
consumptio
n symptoms
Liver, fish, poultry,
meat, peanuts,
whole and
enriched grain
products
Energy production from
foods; aids digestion,
promotes normal
appetite; promotes
healthy skin, nerves.
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.
pellagra, a disease
involving the skin,
gastrointestinal (GI) tract,
and CNS. The symptoms of
pellagra progress through the
three Ds:
dermatitis, diarrhea,
dementia, and, if
untreated, death.
Abnormal
liver function;
cramps;
nausea;
irritability
Stability in
foods
A man with pellagra, which is caused by a
chronic lack of vitamin B3 in the diet
Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine)
Common food
sources
Pork, meats, whole
grains and cereals,
legumes, green, leafy
vegetables.
Major functions
Deficiency
symptoms
the metabolically
active form of vitamin
B6, is involved in many
aspects of
macronutrient
metabolism,
neurotransmitter
synthesis, histamine
synthesis, hemoglobin
synthesis and function
and gene expression.
Pyridoxal phosphate
generally serves as a
coenzyme for many
reactions and can help
facilitate
decarboxylation,
transamination,
racemization,
elimination,
replacement and betagroup interconversion
reactions.
Skin disorders,
dermatitis, cracks at
corners of mouth;
irritability; anemia;
kidney stones; nausea;
smooth
tongue
dietary deficiencies in
pyridoxine are rare but
have been observed in
newborn
infants fed formulas
low in vitamin B6
in women taking oral
contraceptive
 in alcoholics.
.
Overconsumption
symptoms
None known.
Stability in
foods
Considerable
losses during
cooking.
Folacin (folic acid)
Common food
sources
Liver, kidney, dark
green leafy
vegetables, meats,
fish, whole grains,
fortified grains and
cereals, legumes,
citrus fruits.
Major
functions
Deficiency symptoms
Over
consumption
symptoms
Stability in
foods
The human body
needs folate to
synthesize DNA,
repair DNA, and
methylate DNA as
well as to act as a
cofactor in
biological
reactions
involving folate.
It is especially
important in
aiding rapid cell
division and
growth, such as in
infancy and
pregnancy, as well
as in "feeding"
some cancer.
Inadequate serum levels of
folate can be caused by
increased demand for
folate as in pregnancy
and lactation,
Poor absorption of
folate caused by
pathology of the small
intestine.
Megaloblastic anemia is a
primary result of folic acid
deficiency causes
diminished synthesis of
purines and thymidine,
which leads to an
inability of cells to
make DNA and,
therefore, they cannot
divide.
Neural tube defect
May mask
vitamin B12
deficiency
(pernicious
anemia).
Easily
destroyed by
storing,
cooking and
other
processing
Cobalamin ,Vitamin B12
Common food
sources
Major functions
Deficiency
symptoms
Found only in
animal foods:
meats, liver,
kidney, fish, eggs,
milk and milk
products, oysters,
shellfish.
a key role in the
normal functioning
of the brain and
nervous system, and
for the formation of
blood.
It is normally
involved in the
metabolism of every
cell of the human
body, especially
affecting DNA
synthesis and
regulation,
fatty acid synthesis
and energy
production.
Pernicious
anemia, anemia;
neurological
disorders;
degeneration of
peripheral nerves
that may cause
numbness,
tingling in fingers
and toes.
Over
consumption
symptoms
None
known.
Stability in
foods
Biotin
Common food
sources
Liver, kidney,
egg yolk, milk,
most fresh
vegetables, also
made by
intestinal
bacteria
Major functions
Biotin is a
coenzyme in
carboxylation
reactions, in
which it serves
as a carrier of
activated carbon
dioxide.
Helps release
energy from
carbohydrates;
aids in fat
synthesis.
Deficiency
symptoms
Uncommon
under normal
circumstances;
fatigue; loss of
appetite,
nausea,
vomiting;
depression;
muscle pains;
anemia
Over
consumption
symptoms
Stability
in foods
Pantothenic acid
Common food
sources
Major functions
Deficiency
symptoms
Liver, kidney,
meats, egg yolk,
whole grains,
legumes; also
made by
intestinal
bacteria.
synthesize
coenzyme-A
(CoA), as well
as
to
synthesize and
metabolize
proteins,
carbohydrates,
and fats.
Uncommon
due to
availability in
most foods;
fatigue;
nausea,
abdominal
cramps;
difficulty
sleeping.
Over
consumption
symptoms
Stability in foods
About half
of
pantothenic
acid is lost
in the
milling of
grains and
heavily
refined
foods.
Chemical Communications
What Molecules Are Involved in Chemical
Communications?
Two systems share major responsibility for
regulating body chemistry
the endocrine system and the nervous system.
 The endocrine system depends on hormones,
chemical messengers that circulate in the
bloodstream.
The nervous system relies primarily on a much
faster means of communication—electrical
impulses in nerve cells. But the nervous system
also has its chemical messengers, the
neurotransmitters that carry signals from one
nerve cell to another and from nerve cells to their
targets, the ultimate recipients of the messages.
There are three principal types of molecules for
communications:
• Receptors are protein molecules on the surface of
cells embedded in the membrane.
• Chemical messengers, also called legends,
interact with the receptors. (chemical messengers
fit into the receptors sites in a manner reminiscent
of the lock-and-key model)
• Secondary messengers in many cases carry the
message from the receptor to the inside of the cell
and amplify the message.
If your house is on fire and the fire threatens your
life, external signals- light, smoke, and heat –
register alarm at specific receptors in your eyes,
nose, and skin.
From there the signals are transmitted by specific
compounds to nerve cells, or neurons.
Nerve cells are present throughout the body and,
together with the brain, constitute
the nervous system.
In the neurons, the signals travel as electric
impulses along the axons. when they reach the
end of the neuron, the signals are transmitted to
adjacent neurons by specific compounds called
neurotransmitters.
Communication between the eyes and the brain, for
example, is by neural transmission.
What Are Neurotransmitters?
Communication by neurotransmitters is also called
synaptic signaling. This is because the communication
occurs over a juncture (a place where two cells come
into very close contact) called a synapse.
The cell releasing the neurotransmitter is called the
presynaptic cell and the neurotransmitter is
concentrated in an axon terminal of a presynaptic nerve
cell.
The neurotransmitter binds with receptors on the
postsynaptic cell.
An example is acetylcholine released by motor neurons at
the motor end plate which triggers muscle contraction.
As soon as the danger signals are processed in
the brain, other neurons carry messages to the
muscles and to the endocrine gland,
Again, neurotransmitters carry the necessary
messages from the neurons to the muscle cells
and the endocrine glands.
The endocrine glands are stimulated, and a
different chemical signal, called a
Hormone
What are hormones?
 These chemicals are released by
endocrine glands. Hormones are secreted
into the interstitial fluid but then diffuse
into the blood and travel to target cells
throughout the body.
 An example is insulin which regulates
energy metabolism.
The distinction between hormones and
Neurotransmitters is physiological, not
chemical.
Whether a certain compound is considered to be a
Neurotransmitters or hormone depends on
whether it acts over a short distance A cross a
synapse (2 x 10-6 cm), in which case it is
neurotransmitter,
over a long distance (20 cm) from the secretary
gland through the blood- stream to the target cell,,
in which case it is a hormone.
For example, epinephrine and norepinphrine are
both neurotransmitter and hormones.