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Protein & Amino Acids

Explore the components of protein, essential amino acids, protein metabolism, exercise impact, muscle anabolism, and the effects of high protein intake. Understand how protein supports metabolism, structure, and regulation in the body. Learn about the role of amino acids in protein synthesis, degradation, and oxidation. Discover the factors influencing protein requirements and potential adverse effects of excessive protein consumption. Delve into the benefits and limitations of protein supplementation for performance enhancement.

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Protein & Amino Acids

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  1. Protein & Amino Acids

  2. 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

  3. Components of Protein • Peptide bonds: • Amine and carboxyl groups • Dipeptide • Tripeptide • Polypeptide • Protein

  4. 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

  5. Leucine* Isoleucine* Valine* Histidine Lysine Methionine Phenylalanine Threonine Tryptophan Essential Amino Acids *Branched Chain Amino Acids

  6. Functions of Protein • Metabolism • Structure • Membranes • Cytoplasm • Muscle • Regulation • DNA • RNA • Hormones

  7. Protein Metabolism • Four components: 1. Protein synthesis 2. Protein degradation 3. Amino acid oxidation 4. Gluconeogenesis

  8. Protein Synthesis • Dietary protein  digestion  amino acids in blood • Cells use amino acids

  9. 120 g of free AA

  10. 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

  11. Amino Acid Oxidation • Amino acids can be metabolized for ATP • Amine group must be removed • Two ways 1. Deamination -Urea and Krebs Cycle Intermediates 2. Transamination -Krebs Cycle intermediates -Pyruvate  acetyl CoA

  12. TCA Intermediates Pyruvate

  13. Gluconeogenesis • Glucogenic amino acids • Glucose-alanine cycle

  14. Factors Affecting PRO Req. • 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 nursing 4. Disease, infection, trauma 5. Exercise

  15. 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

  16. Exercise and PRO Req. • PRO oxidation during exercise • Endurance • Resistance • PRO breakdown and synthesis during resistance training

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. PRO as an Ergogenic Aid • Amino Acids • Stimulate release of GH? • Stimulate release of insulin • Protein synthesis • Prevents fatigue • Prevent immuno-suppression

  23. 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

  24. Aspartate • Improve aerobic capacity? • Precursor to TCA intermediates and reduces plasma ammonia (cause of fatigue)? • No effect shown in controlled studies

  25. 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

  26. 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

  27. 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

  28. High-Risk Groups • Gymnasts • Endurance Runners, especially females • Dancers especially ballet • Wrestlers, especially low weight-classes

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