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Proteins
are the building blocks of any living organism.
They are composed of chains of 20 different
kinds of amino acids. Proteins constitute life
in the form of enzymes, antibodies, hormones,
hair, nail, bone, teeth, hemoglobin (blood
protein), neurotransmitters, skin or as the
basic components of any cell in our body. The
smallest units of proteins (amino acids) fall in
either of the following types:
Essential amino acids:
Essential amino acids are amino acids human body
can not synthesize and there fore they have to
be supplied in the diet. List of essential amino
acids: Valine, threonine, leucine, lysine,
isoleucine, methionine, phenyalanine, and
tryptophan.
Non-essential amino acids:
Non-essential amino acids can be produced in the
body as long as the carbon, hydrogen, oxygen
(from fats or carbohydrates) and nitrogen
components are supplied in the diet. List of
non-essential amino acids: Alanine, cysteine,
glycine, serine, histidine, tyrosine, cystine,
proline,
arginine,
aspartic acid, glutamic acid, and glutamine.
Digestion of protein
Protein digestion
begins in the stomach. Acids secreted in the
stomach denature protein and make it susceptible
to degradation by enzymes. Digestion is
completed in the small intestine where single
amino acids and peptides are absorbed into the
blood stream. Whole protein, not digested, are
also absorbed to the blood stream.
Benefits of protein
Proteins are indispensable for growth and
maintenance of every kind of cell in our body.
Body development, replenishment of lost blood,
healing of wounds and scars, replacement of dead
cells, and hair and nail growth need proteins.
Proteins in the form of enzymes, hormones and
antibodies promote healthy metabolic and
physiological processes, and boost our nervous
and immunity systems. In situations when fat and
carbohydrate food sources are not providing
adequate calories, proteins are degraded to
generate the calories our body needs.
Deficiency of protein
In developed countries,
protein deficiency is not a serious problem. In
developing countries, however, protein
deficiency, called kwashiorkor, is prevalent and
particularly in children. Children deficient in
protein show an array of symptoms that include:
retarded growth, loss of hair and skin color,
slow healing of wounds, poor digestibility,
diminishing of blood protein, draining of fluid
from blood (edema), liver damage, and poor
immunity.
For information on foods rich in protein,
follow these links:
Food sources of protein: animal and vegetable
protein sources and content.
Protein requirement: for kids, adults and
pregnant and lactating women.
Soybean/tofu: nutritional value and health
benefits
Essential and non essential amino acids:
Definitions and Functions
L-Arginine: Food Sources, Health Benefits and
Side Effects
For characterization of protein from animal
nutrition perspective, please read this article:
Crude Protein.
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