Download Chapter 7: Protein

Protein & Amino Acids
Components of Protein
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Amino acid chains (up to 300 AA)
Amino acid consists of:
1. Amine group (NH3+)
2. Hydrogen
3. Carboxyl group (COO-)
4. R side chain
Components of Protein
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Peptide bonds:
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Amine and carboxyl groups
Dipeptide
Tripeptide
Polypeptide
Protein
Components of Protein
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Twenty different amino acids
Essential (9) & nonessential (11)
Complete vs. noncomplete protein
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Animal vs. vegetable
Complementary proteins
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Beans & Rice
Beans & Corn or Wheat
Peanut butter & Bread
Essential Amino Acids
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Leucine*
Isoleucine*
Valine*
Histidine
Lysine
*Branched Chain Amino Acids
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Methionine
Phenylalanine
Threonine
Tryptophan
Functions of Protein
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Metabolism
Structure
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Membranes
Cytoplasm
Muscle
Regulation
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DNA
RNA
Hormones
Protein Metabolism
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Four components:
1. Protein synthesis
2. Protein degradation
3. Amino acid oxidation
4. Gluconeogenesis
Protein Synthesis
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Dietary protein  digestion 
amino acids in blood
Cells use amino acids
120 g of free AA
Protein Degradation
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Cells break down
Protein not stored
Removal of catabolized PRO
needed
Blood  liver (deamination)
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Excreted as urea
Converted to fat or CHO
Oxidized as energy
Amino Acid Oxidation
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Amino acids can be metabolized for ATP
Amine group must be removed
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Two ways
1. Deamination
-Urea and Krebs Cycle Intermediates
2. Transamination
-Krebs Cycle intermediates
-Pyruvate  acetyl CoA
TCA
Intermediates
Pyruvate
Gluconeogenesis
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Glucogenic amino acids
Glucose-alanine cycle
Factors Affecting PRO Req.
RDA
1.
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7-14 yr: 1.0 g/kg
15-18 yr: 0.9 g/kg
>18 yr: 0.8 g/kg
2. Total energy intake
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As energy inc., PRO req. as % decreases
3. Pregnancy and nursing
4. Disease, infection, trauma
5. Exercise
Characteristics of Skeletal Muscle
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Comprises 40-45% of body weight
Contains 50% of total body protein
Composed of water & protein in 4:1
ratio
Body protein turns over at 3-4
g/kg/day
Skeletal muscle turns over at 1
g/kg/day
Skeletal muscle is 25% of total
turnover
Exercise and PRO Req.
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PRO oxidation during exercise
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Endurance
Resistance
PRO breakdown and synthesis
during resistance training
PRO Oxidation During Exercise
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Endurance training  Inc. muscle
mitochondrial protein enzymes (leucine
oxidation)
Typically 5%-15% of resting
metabolism
Prolonged endurance ~ 10% max
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Depletion of glycogen
Protein not from contractile protein
Recommendation is 1.2-1.8 g/kg
PRO and Strength Training
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Resistance training  PRO
breakdown
Resistance training does not
increase protein oxidation
significantly
Next 24-48 hrs.  protein
anabolism
Also needed for recovery/repair
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Eccentric
Recommendation is 1.6-1.7 g/kg
Protein and Muscle Anabolism
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1 lb muscle contains 100 g protein
(22%)
Reasonable muscle gain is 1
lb/week
Additional 14 g per day protein or
0.14 g per kg for 100 kg individual
400-500 kcal/day to support
additional tissue growth
How much is 70-90 g of PRO?
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6 oz. Chicken breast = 48 g
1 cup skim milk = 8 g
½ cup peanuts = 18 g
2 oz. Cheddar cheese = 14 g
Grand total = 88 g
Potential Adverse Effects of High
Protein Intake (>3 g/kg/day)
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Increased saturated fats and
cholesterol
Liver/kidney damage(?) especially
if already exits
Ketosis
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Dehydration (increase nitrogen)
Diabetic population
Urinary calcium
Performance
PRO as an Ergogenic Aid
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Amino Acids
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Stimulate release of GH?
Stimulate release of insulin
Protein synthesis
Prevents fatigue
Prevent immuno-suppression
Arginine, Lysine, Ornithine
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Increases GH (30 g/30 min)
Increases insulin (but not as much
as CHO ingestion)
Does it work?
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Tolerable oral doses (1-2 g/day) have
less effect than exercise
Large oral doses cause severe GI
disturbances
Aspartate
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Improve aerobic capacity?
Precursor to TCA intermediates
and reduces plasma ammonia
(cause of fatigue)?
No effect shown in controlled
studies
Branched-Chain Amino Acids
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Leucine, isoleucine, valine (essential
AA)
Oxidized during exercise
Oral administration can spare
protein?
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CHO is better source to spare protein
Oral administration can reduce
fatigue?
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Reduces serotonin levels in brain to
reduce fatigue.
No support in controlled studies
Central Fatigue Hypothesis
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Low glycogen and hypoglycemia 
inc. gluconeogenesis
Inc. gluconeogenesis  dec. BCAA
High f-TRP and low BCAA (high fTRP:BCAA ratio)
Increases f-TRP in brain  inc.
serotonin  inc. sensation of
fatigue
Glutamine
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Proposed effects
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Improved hydration?
Improved immune system?
Improved muscle synthesis?
Stimulation of glycogen resynthesis?
Reduction in muscle soreness and improved
tissue repair?
Controlled studies have not shown
documented effects
High-Risk Groups
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Gymnasts
Endurance Runners, especially
females
Dancers especially ballet
Wrestlers, especially low weightclasses