2. • Proteins have an amino group, an acid, a
hydrogen, carbon molecule and a carbon
side chain.
• Protein means primary or first and are
necessary for life.
• Amino means contains nitrogen (NH2).
• Proteins can also contain sulfur,
phosphorus or iron.
4. Amino Acids
• Nonessential amino acids
–a.k.a dispensable amino acids can
be made within the body
• Essential amino acids
–a.k.a indispensable amino acids
must be obtained from foods
• Conditionally essential amino acids
are needed from food sources if the
building blocks to make them are not
available.
8. Ph of Amino Acids
• Most amino acids are neutral with an
aliphathic (single chain) or aromatic chain.
• Two are dibasic with two amino groups:
–Histidine and arginine
• A few are diacidic and are commonly used
as components of proteins in cell
membranes
9. RDA’s ARE EXPRESSED AS
PROTEIN
• The biological requirement is for
amino acids
• Amino nitrogen is about 16% of the
weight of proteins
• Nitrogen content x 6.25 = protein
content of foods or tissue
10. Proteins
• Peptide bonds connect the acid
end of one amino acid with the
amino end of another.
• They are the links that form a
protein chain, which can be
simple or very complex.
12. Proteins
• A Tripeptide consists of three
amino acids linked together.
• When there are three or more
amino acids, the protein starts
to form three dimensional
shapes.
14. Proteins
• Amino acid sequences can vary
resulting in almost an endless
number of combinations.
• Each protein’s sequence is
determined by the DNA
• As each amino acid has unique
chemical characteristics and
electrical charges, the resulting
shapes can be very complex.
15. Denaturation
• Protein denaturation happens when a
protein changes its shape, usually
uncoiling.
• This changes its function and
properties.
• An egg is mostly liquid until cooked.
Milk becomes yogurt or or cheese
when acids or enzymes are added.
• Heat, acids, bases, alcohol, heavy
metals, enzymes or other agents can
cause denaturation.
16. Protein Digestion
• Stomach releases HCL, which
denatures (uncoils) protein strands
and converts the inactive form of
pepsinogen into the active form
pepsin.
• Pepsin breaks the proteins into
smaller polypeptides
• Pepsin is one of thousands of
enzymes, which allows chemical
reactions to take place in the body
without being affected itself.
17. Small Intestine
• Releases pancreatic and
intestinal proteases.
• These hydolyze the polypeptides
further into tripeptides,
dipeptides and finally amino
acids, which are actively
transported into SI cells and
then released into the blood
stream.
19. Protein Absorption
• Carriers - cells of the villi of the SI
have gates through which carrier
substances transport the amino
acids.
• Capillaries, which are the smallest
branches of the circulatory system
carry the free amino acids from the
villi throughout the body.
• Absorption misconceptions
– Enzyme/amino acid supplements
20. • Messenger RNA from the nucleus
and Ribosomes within cells assemble
the free amino acids into proteins
• As the ribosome moves along the
mRNA, an enzyme bonds one amino
acid to another.
• 40 to 100 amino acids can be added
to a growing protein strand in one
second.
21. Protein Synthesis
• DNA in the cell nucleus gives mRNA
the instructions.
• mRNA goes into the cellular fluid and
attaches itself to ribosomes
• transfer RNA carries free amino acids
to the mRNA
• Ribosomes move along the mRNA
allowing enzymes to bond one amino
acid to another until the completed
protein is finished and released.
24. Protein Synthesis
• When a cell makes a protein it is said
that that gene is expressed.
• Nearly all the body’s cells can make
all human proteins, but each type of
cell makes only the kinds of proteins
it needs.
25. Roles of Proteins
• Building material
–Growth, a matrix of protein
underlies almost all structures in
the body including bones,muscles
ligaments, tendons, connecting
matrix between cell walls, scar
tissue, hair and nails.
–Maintenance, GI tract cells are
replaced every three days. The
whole body has its cells renewed
every seven years.
26. Proteins as Enzymes
• Enzymes are usually composed of a
protein, a vitamin and a trace mineral.
• They act as catalysts, allowing reactions to
occur more quickly and efficiently.
• They can cause two substances to come
together making a new structure or can
split a compound apart.
• An enzyme is not affected by the chemical
reactions it allows to take place.
29. Roles of Proteins
• Regulation of fluid balance
–Dependent edema may be caused
when there is too much fluid
between cells and not enough
hydrophilic protein within the cells.
• Acid-base regulation, proteins act as
buffers accepting and releasing
hydrogen ions thus preventing
acidosis or alkalosis.
31. Proteins in Immunity
–Antibodies are giant proteins that
bind up specific invaders like
viruses or antigens
–Antigens are substances that cause
the body to produce antibodies.
They may include bacteria,
allergens, toxins or anything that
causes an inflammatory response.
32. Roles of Proteins
• Source of energy. The brain and
nervous system must have glucose.
Once the amino group is removed
from the protein, the remaining
carbon molecules can be used to
create energy - 4 Kcal per gram or
stored as fat.
• Other roles include being converted
to other proteins or making
neurotransmitters norepinephrine
and epinephrine, melanin, fibrin and
as precursor to the vitamin niacin.
33. Roles of Proteins
• Other roles include being converted
to other proteins or making:
–neurotransmitters norepinephrine
and epinephrine
–melanin
–fibrin
–precursor to the vitamin niacin.
34. Protein Metabolism
• Protein turnover
– Amino acid pool includes free amino
acids from endogenous or exogenous
sources
•Nitrogen balance
– Positive nitrogen balance during growth
or when building new tissue
– Negative nitrogen balance if burned,
fever, injury, infection or starvation.
35. Protein Metabolism
• Using amino acids to make proteins.
– Cells can dismantle one amino acid
and combine the amino group of that
amino acid with carbon fragments
from glucose metabolism to make
another essential or nonessential
amino acid needed.
36. Protein Metabolism
• Deamination is the removal of the
nitrogen containing amino group,
converting it to ammonia, which is
sent to the liver and converted into
urea. The remaining carbon fragment
may be burned or stored as fat.
• Amino acids can be used to make fat
by removing the amino group and
converting the remaining carbon
fragments to fat.
37. Amino Acid Pool
• Proteins are degraded and resynthesized
continuously
• Several times more protein is turned over
daily within the body (endogenous) than is
consumed (exogenous)
• AA consumed in excess or unable to be
used are not stored. They are:
–degraded into urea, uric acid, and
creatinine
–lost in feces or sweat
–converted into hair and nails
38. Reference Proteins
• Nitrogen balance studies within age groups
• Used data for highy digestible, high quality
proteins - egg, meat, milk or fish
• Amino acid scoring patterns were factored in
• A margin of safety of 2 standard deviations
to meet needs of 97.5% of the population
• For adults over age 19 the reference protein
intake is 0.75 g/kg/day (RDA is 0.8)
• Range was 0.54 - egg to 0.99 - vegetable
based diet
39. Protein-Energy
Malnutrition (PEM)
• Acute PEM when one is recently
deprived of food. Children are thin
for their height.
• Chronic PEM from long term food
deprivation. Children are short
for their age.
40. Protein-Energy Malnutrition
• Marasmus - inadequate energy and
protein over a long period of time.
Often seen at 6-18 months of age.
Look like little old people.
•Kwashiorkor - “the evil spirit that
infects the first child when the
second child is born.” Sudden
deprivation at 18 mon to 2 yrs.
• Marasmus-kwashiorkor mix: edema
of marasmus with wasting of
kwashiorkor
41.
42.
43. Protein-Energy Malnutrition
• Infections: Antibodies needed to
fight infections are degraded to
provide amino acids for survival.
–Dysentery with concomitant
diarrhea robs the body of needed
nutrients.
• Rehabilitation: electrolytes especially
potassium and sodium are given
slowly over the first 2 days, then
foods may be started in small
quantities.
44. Health Effects of High Protein
• Heart disease: diet high in animal
protein may contribute to a higher
incidence of heart disease in the U.S.
High homocysteine level possibly from
suboptimal B12, B6 and/or folic acid is
associated with heart disease.
• Cancer of the colon, breast, kidneys,
pancreas and prostate is associated
with high animal protein and fat diet.
• Adult bone loss. Calcium excretion
rises as protein intake increases.
45. Health Effects of High
Protein Diet
• Weight control helpful for some not all
• Any diet in which grains are severely limited
should supplement with manganese 5
mg/day and selenium 200 ug
• Kidney disease - a high protein diet
increases the load on the kidneys, which in
Chinese medicine means degenerative
changes will take place earlier. We are as
old as our back is flexible and our kidneys
function adequately.
46. Recommended Intakes
• RDA
– 0.8 g/kg/day for healthy adults
– 8-11% - of energy intake per day
– 50-65 grams of protein per day or
between 200 to 250 Kcal.
– If junk food, sugar and fat is
restricted, it is difficult not to get
enough protein.
47. Recommended Intakes
• Calculate own: wt (lbs) divided by 2.2
x .8
• Adequate intake - if total Calories are
too low, protein will be used to meet
Calorie needs
• Protein in abundance
48. Supplements
• Protein supplements- very active athletes
may benefit from an intake of 1 gm of
protein per kg rather than .8 gm/kg of body
wt. (75 gm instead of 63 gm/day - 1 1/2 oz
more meat)
• Amino acid supplements
– if not balanced may lead to deficiencies of
some AA thru competition with carrier
enzymes
– Lysine up to 3 gm a day may suppress
herpes infection (divided doses with
meals)
