Proteins and
Amino Acids
What are proteins?
What are the functions of proteins?
Why are amino acids important?
What happens when there is a protein deficiency?
What are proteins?
Proteins
are made up of essential and non-essential amino acids.
http://www.piercenet.com/media/ProStructureFig1.gif
Construction and
maintenance of the
body's tissues is a
major function of
protein.
Building and
repairing cells
proceeds best when
all nine essential
amino acids are
present.
http://jocelyncofer.blogspot.com/2010/08/photos.html
Appropriate combinations
of plant foods can supply
sufficient quantities of all the
essential amino acids.
Protein has the
most positive
image of any of the
macronutrients.
Nearly everyone in
the US consumes
enough protein
Brown, Nutrition Now, 6th ed, p. 15-2
http://www.usda.gov/oce/forum/2012_Speeches/Smith.ppt
15% of calories
is the average
protein consumption.
10 - 35% is the RDA
for all age and sexes.
Why might this level of
protein not be
beneficial to health?
High protein diets
are often high fat and low fiber.
High protein diets
increase excretion of calcium.
Low calcium intake is a risk
factor for developing
osteoporosis later in life.
What are the
functions of protein?
Proteins provide the building material for
cells.
Protein
is required for
growth and
maintenance of
muscles.
Enzymes:
proteins that
act as
catalysts to
speed up the
reactions in
the body.
eg. digestive
enzymes such as
lipases, trypsin and
renin
Hormone:
A substance, usually a protein or steroid, produced by
one tissue and conveyed by the bloodstream to
another.
Hormones affect the body’s metabolic processes,
such as glucose utilization and fat deposition.
Thyroid
hormone
regulates the
metabolic rate
of the body &
controls body
temperature.
Insulin
maintains blood
glucose levels.
Eli Lilly and Company Archives
Tissue maintenance and repair
is an important function of protein.
Immunity: Proteins function as
antibodies, part of the body's immune
system.
Red blood cells and fibrin
(which helps blood clot) are
made primarily from protein.
Maintenance of the acid-base balance
(the pH) of the body is an important protein function.
Energy
is provided by protein,
but protein is not the
best source of
calories.
4 kcal of energy
is provided by
every gram of protein.
What happens when amino
acids are broken down?
Amino acids
are made of two
important parts: the
amino group and the
carboxylic acid.
Acid
Amino
http://commons.wikimedia.org
Amino acids are broken down,
and the amino group is
removed and used elsewhere,
or excreted as urea.
Urea can be harmful if it builds up
in the body.
http://commons.wikimedia.org
Carbon, hydrogen, and oxygen
are used to synthesize
carbohydrates or fats in the body.
http://commons.wikimedia.org
5 – 6.5 ounce equivalents
of protein per day are needed
for healthy adults.
Excess ingested protein
is converted to fat.
Protein contributes
to satiety,
the state of no longer
desiring to eat, more
so than other
macronutrients.
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http://www.nextgenerationfood.com/
Why are amino acids
important?
Amino acids are the
“building blocks”
of proteins.
Enzymes of small
intestine and pancreas
digest protein into smaller
fragments and free amino
acids.
Intestinal enzymes
break protein fragments
into free amino acids.
Brown, 2011.
Amino Acids
•There are 20 common amino acids, nine of
which are essential
•Every protein is a unique combination of
amino acids. With 20 different amino acids
there can be thousands of proteins just like
26 English alphabet letters make a whole
language
PVT TIM HLL:
The Essential Amino Acids
Phenylalanine
Valine
Threonine
Tryptophan
Isoleucine
Methionine
Histidine
Leucine
Lysine
The Non-Essential Amino Acids
Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine
Protein quality:
The ability of proteins in food to support tissue
construction in the body varies depending on the source
of the protein
High quality proteins contain
all essential amino acids.
If any essential amino acids are
missing, the body will not be
able to make some proteins.
Example: insulin
Glycine-isoleucine-valine-glutamateglutamine-cystine-cystine-threonineserine-isoleucine-….
Complete proteins
include meat, milk, fish
and eggs.
Complete proteins:
Food sources of high quality
protein.
Individual plant proteins
are generally considered
“incomplete” Incomplete
proteins:
Proteins that lack one or
more essential amino
acids.
Eating a combination of protein
from plants to “complement” each
other is a good way to get all of the
essential amino acids.
Vegetarian diets
can provide adequate amounts of complete proteins.
If a vegetarian eats dairy
and/or egg products,
they get complete proteins.
Key is consumption of a variety of foods
from complementary protein sources.
Complementary Protein Combinations
Protein/amino acid supplements
may be used to try and build muscle mass.
But there is little evidence
that these supplements or powders alone build muscle mass.
Amino acid supplements
can be harmful
to health.
Worsening
of diseases such as
schizophrenia,
hardening of the
arteries, impair fetal
growth and
development
Supplements
are also
associated with
nausea, vomiting,
bad breath, and
constipation.
Some amino acids may be
used to manage certain
conditions.
Melatonin,
a derivative of tryptophan
can promote sleep.
May be used to try
and build muscle
mass, but there is
little evidence that
amino acid or protein
powders build muscle
mass by themselves
Consuming up
to 20 grams
of high quality protein
immediately after a
resistance exercise may
enhance muscle
building.
70%
of the protein that we consume
comes from meats, milk, and
other animal products.
Dried beans and grains
are also useful sources of protein.
Vitamins and minerals
are also provided with proteins.
What happens when there
is a protein deficiency?
Protein deficiency
leads to loss of muscle
tissue, growth
retardation, reduced
resistance to disease,
weakness, edema, and
kidney and heart
problems.
Two major forms
• Kwashiorkor
• Marasmus
Kwashiorkor:
“the disease that the first child
gets when the new child comes”
Develops rapidly
http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Leukotr/FUNCTION.HTML#kwashiorkor
Kwashiorkor
Kwashiorkor
is related to a marginal
protein-calorie
malnutrition (PCM) and
occurs in children with
an existing disease.
Kwashiorkor
Such children have mild to
moderate weight loss
(60-80% of normal weight
for age), but maintain
some muscle and
subcutaneous fat.
A child often exhibits
edema (swelling) and looks
fat but it is mostly water.
Marasmus
is a severe
deficiency of protein
and calories protein-calorie
malnutrition (PCM)
http://medicalpicturesinfo.com/
Marasmus is generally
accompanied by multiple
vitamin and mineral
deficiencies due to limited
food intake.
Patients exhibit severe
weight loss, wasting of
muscle and body fat, and
severe growth impairment
(less than 60% of normal
weight for age).
Marasmus develops
gradually.
Marasmus occurs frequently
in areas of the world where
hunger and famine are common.
http://emedicine.medscape.com/article/984496-overview
Meat protein consumed increases,
as countries become more affluent.
http://chartsbin.com
Global increased protein intake is
associated with a increase in the
consumption of fat and the “Western
civilization” diseases (i.e., heart disease
and cancer).
Distribution of protein
in the US Diet
Distribution of Protein in the US Diet
% Protein
80
70
60
50
40
30
67
50
50
33
20
10
0
1900
2000
Year
Plants
Animals
Take Home Message:
Adequate intakes of protein without excess levels of fat
can easily be obtained from diets that include dried
beans, cereals, and other grains as sources of proteins
as well as lean meats and low-fat dairy products.
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