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PROTEIN
Protein Structure
Polymer of amino acids
amine group (N)
acid group
side chain
Protein Structure
Proteins are unique among energy
nutrients
They contain NITROGEN
Composed of 20 different amino acids
9 amino acids are essential, other 11
are not essential
Proteins are strands of amino acids
linked by a peptide bond with next
amino acid
Glucose
Triglyceride
Protein Structure
Primary Structure
Amino acid sequence or strand
like a strand of pop-beads or pearls
Secondary Structure
coiling of the strand
like a slinky: positive and negative
parts attract each other
Protein Structure
Tertiary or third level of structure
Folding back of coil
The slinky gets messed up
Quaternary or fourth level of
structure
Subunits fit together
Hemoglobin has four subunits to
make the functional molecule
Protein Structure
SHAPE DETERMINES
FUNCTION
The shape of the protein molecule
determines if the molecule is
functional
the shape of the lipase molecule
determines if it will actually help
breakdown a lipid
Protein Structure
Change of shape is called
DENATURATION
What causes change of shape?
acid (like the stomach low pH) or
base(high pH)
alcohol
mechanical agitation(beating an egg
white)
heat(heat an egg white) or heavy
metals(mercury)
Denaturation
Cellular Protein Synthesis
DNA: in nucleus: acts as a template for
mRNA
mRNA moves out of nucleus to cytoplasm
Carries instruction for an amino acid sequence for a
specific protein to a ribosome
Ribosome ‘reads’ the mRNA which dictates which
amino acid is next
tRNA carries the correct amino acid to the mRNA
Cellular Protein Synthesis
tRNA’s line up one after the other with
amino acids
Amino acids form peptide bonds to make
the primary sequence of the protein
Protein then coils to form the secondary
and tertiary structure
SHAPE DETERMINES FUNCTION
How Are Proteins Made?
Heredity Factor
Cystic fibrosis
Hypercholesterolemia
LDL-receptor
Sickle cell anemia
Sickle-cell hemoglobin
Protein Digestion
Stomach
Denaturation
Pepsin induced breakdown into shorter
‘peptides’
Small Intestines
duodenum: peptidases or proteases enter
from pancreas thru the common bile duct
breakdown proteins to aa’s, dipeptides
and tripeptides
Protein Digestion
Cells of small intestine
complete digestion of proteins so
that only amino acids remain
cells of S.I. absorb amino acids
and a few larger peptides and
release them into the blood for
circulation
Protein Function
Structure proteins
Muscle fiber protein
Connective proteins
others
Protein: Function
Supporting Growth and
Maintenance
body needs amino acids to grow
new cells and replace cells that
are worn out
Protein: Function
Building Enzymes, Hormones,
and other Compounds
amino acids used to make
enzymes (e.g.. lipases for
digestion)
amino acids used to make some
hormones(e.g.. insulin for
glucose metabolism)
Protein: Function
Building Antibodies
antibodies are formed from amino
acids to defend against foreign
proteins and substances in the body
Maintaining fluid and electrolyte balance
Proteins act like magnets and hold
water in the blood vessels and also
electrolytes like sodium
Transport Proteins
Cellular content differ from the
contents of the surrounding
environment: fluids and
electrolytes
Protein Membrane carriers provide
a ‘pump’ to maintain this difference
Sodium-Potassium Pump
Animation of the Sodium-Potassium Pump
Protein: Function
Maintain acid-base balance
.
proteins buffer the blood against
big changes in pH so body
remains pretty neutral
Protein: Function
Providing Energy
When insufficient CHO and Fat are
eaten, the body takes apart
Protein for energy
Nitrogen portion removed from
A.A. and the rest is oxidized for
energy. Nitrogen ends up in the
urine as urea
Amino Acid Possibilities
Can be added to other A.A.’s to make a
protein
Can have Nitrogen removed
then it can be oxidized for energy or
made into glucose (glucogenesis) or
made into fat (lipogenesis)
The diet needs to supply the 9 essential
amino acids and 0.8 grams protein/kg
wt.
Protein Quality, Use and
Need
Protein Quality
the amino acid assortment greatly
influences a protein’s usefulness
to the body
Protein Quality, Use and
Need
Measuring Protein Quality
the amount of the essential amino acids
present in the protein
If all are well represented, the protein will
support growth and maintenance:
COMPLETE PROTEIN
If not, it won’t support growth: POOR
QUALITY PROTEIN
Protein quality
Complete or good quality proteins
soy beans, milk protein, animal flesh
Poor quality proteins
grains (missing lysine, an essential amino acid)
many legumes(beans, missing methionine)
Mutual Supplementation or complementing
proteins
mix grain and legume and get a good quality protein
eg: corn tortilla and refried beans
Vegetarian Diets-Reasons
Health
Religion
Ethical
Environmental
Taste
Types of Vegetarian Diets
Non-red meat vegetarian
poultry, fish, dairy, eggs O.K
no special nutritional problems,
may be high in fat, saturated fat
Lacto-ovo vegetarian
milk and eggs O.K.
no special nutritional problems
may be high in fat, saturated fat
Vegetarian Diets: Types
Strict Vegetarian: Vegan
no animal products
protein quality-complement
calcium
iron
vitamin B 12
Top Stories - The Olympian Olympia, Washington
Vegetarian vs Meat eaters
Vegetarian
Meat eaters
reduced risk
growth
support during
critical times.
obesity
diabetes
hypertension
heart disease
digestive disorders
cancer
Protein RDA: 0.8 grams/kg
Nitrogen balance
negative balance= more out in
urine than coming in from the
diet
protein is being broken down faster
than it is replaced
who is in this predicament? elderly,
bedridden
Protein RDA: 0.8 grams/kg
positive balance=more in
the diet than going out in
the urine
protein is being made into tissue
faster than it is taken apart
Protein Rich Foods
Animal products
also high in vitamin B12, iron, and zinc
lacking in vitamins C and folate
often high in fat
Legumes
soy protein almost “complete”
high in fiber, many B vitamins, iron,
calcium
low in vitamins A, C and B12
Protein Needs
154# (70 kg)
RDA = 70 x .8g/kg = 56 grams
Athlete 1 to 1.5 g/kg (ADA)=
70 to 105 grams Protein/day
Too little Protein
Kwashiorkor: Protein deficiency
true definition: what happens to the first child when
the second child is born
symptoms: edema, ascites(swollen belly)
immune system failure so many infections
loss of pigmentation
Phenylalanine to Tyrosine to Melanin is
blocked
Fatty Liver
no lipoproteins to carry fats and accumulate
in liver
Too Much Protein
Dehydration
100 Cal of extra protein takes 350
grams(12 oz) of water to clear( this is
how many grams of protein?)
100 Cal of extra CHO or Fat only takes
50 grams of water to clear
Coupled with heavy workouts may
result in dehydration
Protein needs of Athletes
May be up to 1.7 for power athletes
May be up to 1.4 grams/kg for endurance
athletes
Tour de France, marathoners,
triathletes
They may need every available
source of energy they can get their
hands on