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Exercise Metabolism3
Estimation of Fuel Utilization During Exercise
| Question | Answer |
|---|---|
| Respiratory exchange ratio (RER or R) | R= (VCO2/VO2) |
| R for fat (palmitic acid) C16H32O2 + 23 O2 = 16 CO2 + 16 H2O | R= (VCO2/VO2)= (16 CO2/23 O2)=.70 |
| R for carbohydrate (glucose) C6H12O6 + 6 O2 = CO2 + 6 H2O | R= (VCO2/VO2)= (6 CO2/6 2)= 1.00 |
| the ratio of carbon dioxide produced to the oxygen consumed (VCO2/VO2)is the | respiratory exchange ratio (R) |
| only during _____-____ ____ are the VCO2 and VO2 reflective of _______ ________ of gases in tissues. | steady-state exercise; metabolic exchange |
| In order for R to be used as an estimate of substrate utilization during exercise, the subject must have | reached steady state. |
| Low-intensity exercise (<30% VO2 max) | Fats are primary fuel |
| High-intensity exercise (>70% VO2 max) | Carbohydrates are primary fuel |
| “Crossover” concept | Describes the shift from fat to CHO metabolism as exercise intensity increases |
| “Crossover” concept is due to | * Recruitment of fast muscle fibers * Increasing blood levels of epinephrine |
| The Regulation of Glycogen Breakdown During Exercise is Dependent on the enzyme _______. | phosphorylase |
| How is phosphorylase activated? (2 ways) | 1) The calcium released from sarcoplasmic reticulum activates Calmodulin. Then, active calmodulin activates phosphorylase. 2) Epinephrine binding to receptor results in formation of cyclic AMP; to which Cyclic AMP activates phosphorylase. |
| McArdle’s Syndrome | A Genetic Error in Muscle Glycogen Metabolism |
| McArdle’s Syndrome patients cannot synthesize the enzyme _____________ due to gene mutation. | phosphorylase |
| McArdle’s Syndrome patients have the inability to break down ____ ______. | muscle glycogen |
| McArdle’s Syndrome also ______ the production blood lactate levels. | prevents;(do not rise during high-intensity exercise) |
| McArdle’s Syndrome Patients complain of _____ __________ and ______ _____. | exercise intolerance and muscle pain |
| Is Low-Intensity Exercise Best for Burning Fat? | *low intensities (~20% VO2max),approx 60% of energy expenditure is derived from fat. H/e, total energy expended&total fat oxidation are low. *higher intensities (~50% VO2max)~40% of energy from fat. Total energy expended & fat oxidation are higher. |
| Prolonged, low-intensity exercise shift from carbohydrate metabolism toward | fat metabolism |
| Prolonged, low-intensity exercise shift from carbohydrate metabolism toward fat metabolism due to an increased rate of _____. Stimulated by rising blood levels of epinephrine, enzymes called ____ cause the breakdown of triglycerides -> _____ + FFA. | lipolysis;lipases; glycerol |
| ____________ is depleted during prolonged high-intensity exercise | Glycogen |
| Causes for glycogen to deplete during prolonged high-intensity exercise | 1)Reduced rate of glycolysis and production of pyruvate 2) Reduced Krebs cycle intermediates 3) Reduced fat oxidation (Fats are metabolized by Krebs cycle) |
| The depletion of ____ and _____ _____stores contributes to fatigue | muscle and blood carbohydrate |
| During submaximal (<70% VO2 max), long-duration (>90 minutes) exercise, | 30–60 g of carbohydrate per hour are required. Ingestion of carbohydrates can improve endurance performance |
| Sources of Carbohydrate During Exercise | 1)Muscle glycogen- primary source during high-intensity(1st hr) 2)Blood glucose- from liver "glycogenolysis" (Primary source during low-intensity exercise;important during long-duration exercise as muscle glycogen levels decline) |
| Intramuscular triglycerides | Primary source of fat during higher intensity exercise |
| Sources of Fat During Exercise | Intramuscular triglycerides and Plasma FFA |
| How is Plasma FFA made? | From adipose tissue lipolysis Triglycerides --> glycerol + FFA |
| How is Plasma FFA used as energy? | *FFA converted to acetyl-CoA and enters Krebs cycle;becomes more important as muscle triglyceride levels decline in long-duration exercise. |
| Plasma FFA is the | primary source of fat during low-intensity exercise; becomes more important as muscle triglyceride levels decline in long-duration exercise |
| Sources of Protein During Exercise | *Proteins broken down into amino acids *Only a small contribution (~2% or 5-10% during late prolonged exercise) to total energy production during exercise |
| Muscle can directly metabolize branch chain _____ ____ and _______. | amino acids, alanine |
| Liver can convert alanine to ______. | glucose |
| _____ can be used as a fuel source by skeletal muscles and the heart. | Lactate |
| Converted to acetyl-CoA and enters Krebs cycle | Lactate |
| in what cycle can lactate be converted to glucose in the liver? | Cori cycle |
| Lactate produced in one tissue and transported to another | Lactate shuttle |
| Steps to the Cori Cycle using Lactate as the Fuel sorce | 1) Lactic acid produced by skeletal muscle is transported to the liver 2) Gluconeogenesis- Liver converts lactate to glucose 3) Glucose is transported back to muscle and used as a fuel |
| In general, _____________ are used as the major fuel source during high-intensity exercise. | carbohydrates |
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Angelface7717
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