LS2 Lect12

LS2 Lect12 - ENERGY METABOLISM II: ACTIVITY METABOLISM...

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Unformatted text preview: ENERGY METABOLISM II: ACTIVITY METABOLISM Ch. 13, pp. 416 ­439 Prof. Peter Ellison, office hours M 2 ­3 or by appt. GLYCOLYSIS KREB’S CYCLE ANAEROBIC GLUCOSE TO PYRUVATE 2 ATP PER GLUCOSE AEROBIC (INDIRECTLY) GENERATES CO2, REDUCED SUBSTRATES (NADH), AND 2 ATP PER GLUCOSE TRICARBOXYLIC ACID CYCLE OXIDATIVE PHOSPHORYLATION ELECTRON TRANSPORT CHAIN AEROBIC (DIRECTLY) GENERATES H2O (AND HEAT) 34 ATP PER GLUCOSE GLYCOLYSIS KREB’S CYCLE LIMITING FACTORS •  OXYGEN •  FUEL •  MITOCHONDRIAL VOLUME OXIDATIVE PHOSPHORYLATION “PULL” REGULATION “PUSH” REGULATION ENERGY METABOLISM II: ACTIVITY METABOLISM OUTLINE: •  DYNAMIC METABOLISM •  MEASURING ENERGY EXPENDITURE •  VO2max AND AEROBIC CAPACITY •  COST OF TRANSPORT Ch. 13, pp. 416 ­439 Prof. Peter Ellison, office hours M 2 ­3 or by appt. IMMEDIATE ENERGY DEMAND ATP ANAEROBIC GLYCOLYSIS ENERGY PCr AEROBIC METABOLISM TIME Immediate energy demand ATP (“steady state”) aerobic metabolism Energy Oxidative phosphorylation PCr Glycolysis 2 ­5 30 ­45 sec sec Time 2 ­5 min SUBMAXIMAL WORK SUPRAMAXIMAL WORK IMMEDIATE ENERGY DEMAND ATP ENERGY PCr ANAEROBIC GLYCOLYSIS AEROBIC METABOLISM LACTATE ACCUMULATION TIME REMOVAL OF LACTIC ACID REQUIRES 6 MOL ATP PER MOL LACTATE IMMEDIATE ENERGY DEMAND ATP ENERGY PCr AEROBIC METABOLISM ANAEROBIC GLYCOLYSIS •  WHERE DOES THE FUEL COME FROM? •  WHERE DOES THE OXYGEN COME FROM? TIME “THE WALL” PERCENT ENERGY 100 MUSCLE GLYCOGEN 75 50 ADIPOSE TISSUE LIVER GLYCOGEN 25 0 0 100 200 MINUTES 300 RATE OF ATP SYNTHESIS SUBSTRATE RELATIVE RATE PHOSPHOCREATINE 100 MUSCLE GLYCOGEN 55 BLOOD GLUCOSE 23 FATTY ACIDS 10 (ANAEROBIC) (AEROBIC) IMMEDIATE ENERGY DEMAND ATP ENERGY PCr AEROBIC METABOLISM ANAEROBIC GLYCOLYSIS •  WHERE DOES THE FUEL COME FROM? •  WHERE DOES THE OXYGEN COME FROM? TIME hemoglobin heme groups myoglobin 100 PERCENT SATURATION MYOGLOBIN 75 HEMOGLOBIN 50 working muscle capillary 25 arterial blood 0 0 10 20 30 40 PARTIAL PRESSURE O2 (mm Hg) 50 WORK PACING 1.0 6.0 0.9 5.4 0.8 4.8 O2 from Mb 0.43 L O2 (liters) 0.7 O2 defecit 1.91 L 4.2 0.6 3.6 0.5 3.0 0.4 2.4 0.3 O2 from Hb 0.47 L O2 from Mb 0.43 L 1.8 0.2 1.2 0.1 O2 from Hb 3.26 L 0.6 BMR 0.043 L 0.0 10 sec BMR 0.26 L 0.0 60 sec MEASURING ENERGY EXPENDITURE . Open flow respirometry: measurement of steady state VO2 expired gases sampled and pumped to O2 analyzer . The rate of oxygen uptake by the body is denoted by VO2 and expressed in L/min, ogen normalized to body mass as ml/kg/min. . What does VO2 represent? VO2 (ml/kg/min) . VO2max . 450 WATTS 400 WATTS 50 300 WATTS 40 200 WATTS 30 100 WATTS 20 10 0 TIME (100 WATTS ~ 87 kcal/hr) . Direct measurement of VO2max involves a series of . measurements of stable VO2 at increasing workloads unkl an asymptote is reached. Max HR range During aerobic work, heart rate is the principle variable determining oxygen uptake, although the relakonship can vary between individuals. (WHY?) . Because the HR/VO2 relakonship is linear, you can easily use HR to . . eskmate VO2 and you can extrapolate an eskmate of VO2max. Hereditability of VO2 capacity Klissouras et al. J. appl. Physiol. (‘71) (15 pairs identical & 15 pairs fraternal twins) aerobic capacity max. heart rate glycolytic capacity Bouchard et al. Med. Sci. Sports Exer. (‘86) (Larger groups of brothers, identical & fraternal twins) aerobic capacity max. heart rate Training (endurance) versus Δ aerobic capacity: +6 to 30% HERITABILITY 93% 86 81 50% 50 . Comparison of sport training effects on mass-specific maximal VO2 (for male athletes, females ~ 10-15% lower) Resting (gender difference reflects relatively greater body fat in females than males) Sedentary Weight lifters Rowers Cyclists Speed skaters Middle-distance runners Cross-country skiers 0 McCardle, Katch & Katch Exercise Physiology (from Saltin & Astrand, ‘67) 20 60 80 . 40 VO2 max (ml O2/kg/min) 100 (mass-specific to control for effect of size) Muscle fiber types and recruitment red Intermediate White Comparative Animal Energetics DOG COYOTE ELEPHANT AEROBIC SCOPE Res%ng MR aerobic scope Horse Antelope Human Dog Cat . VO2 MAX . resting VO2 30 45 average for endotherms: ~10 10-20 30 4 Energy Energy Species differences in exercise performance VO2 max High aerobic capacity: sustained activity & short recovery res%ng start MR Time Low aerobic capacity: brief bursts activity & prolonged recovery VO2 max end start end Time Energetics of Locomotion: effects of speed, gait & body size . Studied based on measurements of steady state VO2 Effect of speed on rate of energy use . (measure steady state VO2 while person walks & runs on a treadmill) Res%ng MR (metabolic rate) = (Net) cost of transport energy/distance (mlm) 2/m) (J/ O or Joules/m (Exercise Intensity) Cost of transport = Energy/time Distance/time = Energy Distance 60 Prius FUEL EFFICIENCY (MPG) 50 40 Mini 30 20 10 0 Malibu Rolls Royce Lamborghini Hummer 8.00 RATE OF ENERGY USE (Gal/Hr) 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 20 30 40 50 SPEED (MPH) 60 70 80 0.12 Lamborghini COST OF TRANSPORT (g/mile) 0.1 Rolls Royce 0.08 Hummer 0.06 Mini 0.04 Malibu 0.02 Prius 0 2000 2500 3000 3500 4000 4500 CURB WEIGHT (lbs) 5000 5500 6000 (GAL/MILE/KG) * 10,000 NET COST OF TRANSPORT 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Effect of Size (age) on energy cost of running (Energy/distance/kg) Net Transport Cost VO2/kg (Energy/kg/time) . VO2/kg mass-specific energy use Child Adult Slope = Net Transport Cost Child Adult Running Speed (e.g. km/hr) Running (Energy/time) Walking (Energy/distance) Transport Cost VO2 Effect of Gait on human energy cost Cost of Walking Cost of Running (Energy/distance ~ 30 to 50% higher ~ 1.4 m/s Speed (e.g. m/s or km/hr) Bramble & Lieberman Nature 2004 432: 345-352. Endurance running and the evolution of Homo “endurance running is a derived capability of the genus Homo, originating about 2 million years ago” ...
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