Download Lecture 04 Proteins

Proteins and
Vegetarianism
Lecture 5
Units 15, 16
Chemistry
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Composition: C H O N (S)
Amino Acids “building blocks”
– Amine group (NH2)
– Acid group (COOH)
– Differ by side group (“R”)
9
: from food
11 Nonessential AA: can be made from other
AA
Amino Acid, Peptide & Protein
Amino acid
NH2
R
C
Peptide and protein
COOH
AA1-AA2-AA3-AA4--- AAn
Digestion & Absorption
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HCl
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Enzymes split long chain of AA for
absorption
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Blood transports AA to liver & muscle
Functions of Protein
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Growth, build & maintenance of tissues
Regulate body processes:
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Water (fluid) balance--prevent edema
Acid-Base (pH) balance--buffers
Immune system - antibodies
Energy source--4 calories / gram
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Protein Synthesis
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DNA code controls : Which AA needed
What order AA go on new chain
AA3
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AA1 + AA2
AA1AA2
AA1AA2AA3
Requires:
Calories
Essential AA from AA pool
Non-essential AA from synthesis or diet
Process of Protein Synthesis
DNA ------RNA ---- Protein
Transcription
Translation
DNA=deoxyribonucleic acid
RNA=ribonucleic acid
Catabolism of Protein
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Breakdown of protein to AA
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AA converted to fat when
excess AA
N from AA is reused for AA synthesis;
excess is excreted in urine
– May cause loss of Ca in urine
– Kidney disease problem
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Protein Quality
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Complete Protein
High quality
All essential AA in
needed amounts
Animal sources
Incomplete Protein
Plant sources
70% of protein from
animal sources in US
Complementary Protein
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Plant protein
(legume) with
limiting AA
combined with
different plant
protein (grain)
different limiting AA
eaten together give
complete protein
Plants provide Incomplete
Protein
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Low in one or
more ess. AA
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Eat in combo
to “complete”
the AA
balance
Protein Requirements
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.8 gm/kg body weight
Protein RDA
46 gm for women
58 gm for men
10-12% kcal from protein
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Actual US Intake
>80 gm
>110 gm
~17% kcal from protein
Food Sources of Proteins
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Meat
Fish
Poultry
Eggs
Beef & pork rich in
iron but high in
fat
More Good Protein Sources
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Dairy products
select low fat
(butter not protein)
Legumes
Cereal grains
Seeds
Nuts
Plant sources of
protein are low in
fat
What about protein for
athletes?
Athlete needs 1.26 gm /
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Kg (~90 gm)
(but typical US male
eats >110 gm and
female eats >80 gm)
Thus… supplements
not needed
What does the body do
with the added amino
acid?
What builds muscle:
exercise and a good
diet
Amino Acid Supplement
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High intake of a single AA leads to AA
imbalance and is harmful
Many AA supplements on market,
Surplus of AA causes diarrhea, loss of
appetite, GI upsets
Tryptophan supplements were banned
in 1990
Athletes
Vegetarian Diets
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Semi-vegetarian:
– lacto vegetarian
– ovo vegetarian
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Strict vegetarian:
– “Vegan”
– healthy diets use complementary proteins
Macrobiotic diet: locally grown and whole
foods; Yin(“cold”)&yang(“warm”) foods
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Vegetarian Diets & Health
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Associated with low risk of chronic
diseases
May lead to
Vegans: vitamins B12 and D, Ca, Zn are
at risk
Adequately planned vegetarian diets
can
The key to achieve healthy diet: variety
Protein deficiency--Marasmus
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Chronic food
deprivation,diseases
Protein & calories
Impairs brain
development &
learning
Severe weight loss
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Infection, diarrhea
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Protein deficiency -Kwashiorkor
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Deficiency in protein but
not calories
Children 1-3 years
Some weight loss
Edema
Hair: dry, brittle,
changes color (lack of
AA to make melanin)