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Protein & Amino Acids
Components of Protein 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 Peptide bonds:
Amine and carboxyl groups Dipeptide Tripeptide Polypeptide Protein
Components of Protein Twenty different amino acids Essential (9) & nonessential (11) Complete vs. noncomplete
protein Animal vs. vegetable
Complementary proteins Beans & Rice Beans & Corn or Wheat Peanut butter & Bread
Essential Amino Acids Leucine* Isoleucine* Valine* Histidine Lysine
Methionine Phenylalanine Threonine Tryptophan
*Branched Chain Amino Acids
Functions of Protein Metabolism Structure
Membranes Cytoplasm Muscle
Regulation DNA RNA Hormones
Protein Metabolism Four components:
1. Protein synthesis2. Protein degradation3. Amino acid oxidation4. Gluconeogenesis
Protein Synthesis Dietary protein digestion
amino acids in blood Cells use amino acids
120 g of free AA
Protein Degradation Cells break down Protein not stored Removal of catabolized PRO
needed Blood liver (deamination)
Excreted as urea Converted to fat or CHO Oxidized as energy
Amino Acid Oxidation Amino acids can be metabolized for
ATP Amine group must be removed
Two ways
1. Deamination-Urea and Krebs Cycle Intermediates2. Transamination-Krebs Cycle intermediates-Pyruvate acetyl CoA
TCA Intermediates
Pyruvate
Gluconeogenesis Glucogenic amino acids Glucose-alanine cycle
Factors Affecting PRO Req.1. RDA
7-14 yr: 1.0 g/kg 15-18 yr: 0.9 g/kg >18 yr: 0.8 g/kg
2. Total energy intake As energy inc., PRO req. as %
decreases
3. Pregnancy and nursing4. Disease, infection, trauma5. Exercise
Characteristics of Skeletal Muscle
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. PRO oxidation during exercise
Endurance Resistance
PRO breakdown and synthesis during resistance training
PRO Oxidation During Exercise Endurance training Inc. muscle
mitochondrial protein enzymes (leucine oxidation)
Typically 5%-15% of resting metabolism
Prolonged endurance ~ 10% max Depletion of glycogen
Protein not from contractile protein Recommendation is 1.2-1.8 g/kg
PRO and Strength Training Resistance training PRO
breakdown Resistance training does not increase
protein oxidation significantly Next 24-48 hrs. protein anabolism Also needed for recovery/repair
Eccentric Recommendation is 1.6-1.7 g/kg
Protein and Muscle Anabolism 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? 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) Increased saturated fats and
cholesterol Liver/kidney damage(?)
especially if already exits Ketosis
Dehydration (increase nitrogen) Diabetic population
Urinary calcium Performance
PRO as an Ergogenic Aid Amino Acids
Stimulate release of GH? Stimulate release of insulin Protein synthesis Prevents fatigue Prevent immuno-suppression
Arginine, Lysine, Ornithine Increases GH (30 g/30 min) Increases insulin (but not as
much as CHO ingestion) Does it work?
Tolerable oral doses (1-2 g/day) have less effect than exercise
Large oral doses cause severe GI disturbances
Aspartate Improve aerobic capacity? Precursor to TCA intermediates
and reduces plasma ammonia (cause of fatigue)?
No effect shown in controlled studies
Branched-Chain Amino Acids
Leucine, isoleucine, valine (essential AA)
Oxidized during exercise Oral administration can spare protein?
CHO is better source to spare protein Oral administration can reduce fatigue?
Reduces serotonin levels in brain to reduce fatigue.
No support in controlled studies
Central Fatigue Hypothesis Low glycogen and hypoglycemia
inc. gluconeogenesis Inc. gluconeogenesis dec. BCAA High f-TRP and low BCAA (high f-
TRP:BCAA ratio) Increases f-TRP in brain inc.
serotonin inc. sensation of fatigue
Glutamine Proposed effects
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 Gymnasts Endurance Runners, especially
females Dancers especially ballet Wrestlers, especially low
weight-classes