Physiology Week 5 Lecture 10
Physiology Week 5 Lecture 10 IPHY 3470
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This 3 page Class Notes was uploaded by Sydney Lazzell on Friday September 23, 2016. The Class Notes belongs to IPHY 3470 at University of Colorado at Boulder taught by Christopher DeSouza in Fall 2016. Since its upload, it has received 34 views. For similar materials see Human Physiology 1 in integrated physiology at University of Colorado at Boulder.
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Date Created: 09/23/16
IPHY 3470: Human Physiology 1 Week 5 Lecture 10 Chalk Talk ETC o 4 complexes o 2 enzymes: CoQ & Cytochrome C o Location: inner membrane of mitochondria NADH à NAD: C1 --- ADP + P à ATP FADH2: C2 C3 --- ADP + P à ATP C4 --- ADP + P à ATP Fat Metabolism o 3 fatty acids tails o Glycerol backbone o HSL (hormone sensitive lipase) to cleave off fatty acid tails from backbone Lecture Slides Fatty Acid Oxidation o Fatty acids must be “primed” in ATP dependent (2 ATP) acylation step to form fatty acyl-CoA o This acylation step takes place in the cytosol – must get to inner mitochondria matrix for oxidation (need shuttle system) Carnitine Shuttle 1. Acyl group of a cytosolic acyl-CoA is transferred to carnitine – releasing CoA to its cytosol pool 2. Acyl-carnitine transported into matrix 3. Acyl group transferred to CoA molecule 4. Carnitine is returned to cytosol a. Fatty acid chains inside mitochondria Beta Oxidation o Fatty acids are dismembered through beta oxidation of fatty acyl-CoA o Each time around: cleave 2 carbons & kick off 1 FADH2, 1 NADH, 1 acetyl- CoA (goes to Krebs cycle) o Occurring in the matrix of the mitochondria o Final stage: last thing you end up with is acetyl-CoA and 2 carbon atoms shorter than the one that began the cycle o Rate limiting step: last step of oxidation o Product inhibition: acetyl-CoA Energy Yield o Each round of beta oxidation: o 1 NADH, 1 FADH2, 1 acetyl-CoA o Ex: C16 fatty acyl group o # of oxidation cycles: ((n/2)-1) = 16/2-1 = 7 cycles o Yield: 7 FADH2, 7 NADH, 8 acetyl-CoA o 14+21+72+16+8=131 ATP MINUS 2 = 129 ATP o So much more ATP from fat metabolism Glucose Fatty Acid Cycle o Explains how availability of the one fuel source can influence the use of another o Regulate blood glucose levels o Citrate produced from beta oxidation, citrate inhibits PFK, thus slowing glycolysis o Changes in enzymes with energy utilization changes promotes lipid oxidation over glucose utilization during energy expenditure 1. HK: by G-6-P 2. PFK: by ATP & citrate 3. PDH: by acetyl-CoA Substrate Utilization o Work load/power output is the primary factor in determining fuel utilization during exercise o Directly linked to ATP o Resting, post absorbing state energy comes from lipid oxidation (60%), then CHO (30%), and protein (5-7%) o Exercise power output is increased from mild to moderate, further reliance on CHO and lipid utilization declines o 100% max heart rate = burning 100% CHO (high intensity & need ATP immediately) o Crossover Effect o Endurance athletes can move their crossover mark to the right to go longer at a higher intensity while burning fat (increase mitochondria) o Increase intensity = CHO energy source, regardless of training status o o Aerobic Power = Fat and CHO o Endurance athletes are able to suppress glycogenolysis = prolonging time to glycogen depletion & fatigue o Glucose fatty acid cycle functions during mild to moderate § But really functions after exercise that depletes muscle glycogen (switch back to fat metabolism) Effect Lipid Utilization o Skeletal muscle relies on glycolysis & lipid oxidation o Heart & liver highly adapted for lipid utilization o Brain & RBC rely on glycolysis for energy supplies o Heart = fat o Brain = CHO
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