Bioenergetics. and Training

Transcription

1 chapter Bioenergetics of Exercise And Training 2 Bioenergetics of fexercise and Training

2 Key Terms bioenergetics: The flow of energy in a biological system; the conversion of macronutrients into biologically usable forms of energy. catabolism: The breakdown of large molecules into smaller molecules, associated with the release of energy. anabolism: The synthesis of larger molecules from smaller molecules; can be accomplished using the energy released from catabolic reactions. (continued)

3 Key Terms (continued) exergonic reactions: Energy-releasing reactions that are generally catabolic endergonic reactions: Energy-consuming reactions; include anabolic processes and the contraction of muscle metabolism: The total of all the catabolic and anabolic reactions in a biological system adenosine triphosphate (ATP): Allows the transfer of energy from catabolic to anabolic reactions

4 Chemical Structure ATP (a) The chemical structure of an ATP molecule including adenosine (adenine + ribose) triphosphate group locations of the high-energy chemical bonds. (b) The hydrolysis of ATP breaks the terminal phosphate bond releases energy leaves ADP, an inorganic phosphate (P i ), and a hydrogen ion (H + ). (c) The hydrolysis of ADP breaks the terminal phosphate bond releases energy leaves AMP, P i i, and H +. (a) (b) () (c)

5 Biological Energy Systems Three basic energy systems exist in muscle cells to replenish ATP: The phosphagen system (immediate) Glycolysis (lactic acid) The oxidative system AEROBIC ANAEROBIC

6 Biological Energy Systems Phosphagen System Provides ATP primarily for short-term, term, high-intensity intensity activities and is active at the start of all exercise regardless of intensity Would it predominate Why is this active at the if I stood up and beginning gof exercise walked across campus? regardless of exercise intensity? What sports require a well developed phosphagen energy system?

7 Biological Energy Systems Phosphagen System ATP Stores The body does not store enough ATP for exercise. Some ATP is needed for basic cellular function. The phosphagen system uses the creatine kinase reaction to maintain the concentration of ATP. The phosphagen system replenishes ATP rapidly. Control of the Phosphagen System Law of mass action: The concentrations of reactants or products (or both) in solution will drive the direction of the reactions.

8 Biological Energy Systems Glycolysis The breakdown of carbohydrates either glycogen stored in the muscle or glucose delivered in the blood to resynthesize ATP

9 Glycolysis ADP = adenosine diphosphate ATP = adenosine triphosphate NAD +, NADH = nicotinamide adenine dinucleotide

10 The end result of glycolysis gy y (pyruvate) may proceed in one of two directions: 1) Pyruvate can be converted to lactate t ATP resynthesis occurs at a faster rate but is limited in duration. This process is sometimes called anaerobic glycolysis (or fast glycolysis). 2) Pyruvate can be shuttled into the mitochondria The ATP resynthesis rate is slower But it can occur for a longer duration This process is often referred to as aerobic glycolysis l (or slow glycolysis)

11 Questions Why would the terms fast glycolysis and slow glycolysis be inaccurate? Why would the terms anaerobic glycolysis or aerobic glycolysis be inaccurate?

12 Lactate not a bad thing Lactate formation Allows quick synthesis of ATP Pyruvate is accepting excess hydrogen ions (helps to buffer ph changes!) Glycolysis l and the Formation of Lactate t The formation of lactate from pyruvate is catalyzed by the enzyme lactate dehydrogenase. The end result is not lactic acid. Lactate is not the cause of fatigue. Glucose + 2P i + 2ADP 2Lactate + 2ATP + H 2 O

13 Lactate not a bad thing As high intensity exercise progresses, cellular ph rises (metabolic acidosis) Starts to impede cross-bridge interaction Affinity of troponin for Ca 2+? Starts to affect glycolytic reactions Starts to stimulate nociceptors in muscle (feeling of pain)

14 Cori Cycle Lactate can be transported in the blood to the liver, where it is converted to glucose This process is referred to as the Cori cycle

15 Biological Energy Systems Glycolysis Leading to the Krebs Cycle Pyruvate that enters the mitochondria is converted to acetyl- CoA. Acetyl-CoA can then enter the Krebs cycle. NADH molecules enter the electron transport system Glucose + 2P i + 2ADP + 2NAD + 2Pyruvate + 2ATP + 2NADH + 2H 2 O 2 Energy Yield of Glycolysis Glycolysis from one molecule of blood glucose yields a net of two ATP molecules. Glycolysis from muscle glycogen yields a net of three ATP molecules.

16 Biological Energy Systems Glycolysis Control of Glycolysis Stimulated t by high h concentrations ti of ADP, P i, and ammonia and by a slight decrease in ph and AMP Inhibited by markedly lower ph, ATP, CP, citrate, and free fatty acids Also affected by hexokinase, phosphofructokinase, and pyruvate kinase Lactate Threshold and Onset of Blood Lactate Lactate threshold (LT) represents an increasing reliance on anaerobic mechanisms. LT is often used as a marker of the anaerobic threshold.

17 Key Term lactate threshold (LT): The exercise intensity or relative intensity at which blood lactate begins an abrupt increase above the baseline concentration.

18 Lactate Threshold (LT) and OBLA

19 Lactate Threshold and Onset of Blood Lactate Accumulation (OBLA) LT is around 50% to 60% of VO 2max in untrained individuals. LT is around 70% to 80% of VO 2max in trained athletes. OBLA is a second increase in the rate of lactate accumulation. It occurs at higher relative intensities of exercise. It occurs when the concentration of blood lactate reaches 4 mmol/l.

20 Biological Energy Systems The Oxidative (Aerobic) System Primary source of ATP at rest and during lowintensity activities Uses primarily carbohydrates and fats as substrates Glucose and Glycogen Oxidation Metabolism of blood glucose and muscle glycogen begins with glycolysis and leads to the Krebs cycle NADH+H + and FADH 2 molecules transport hydrogen atoms to the electron transport chain, where ATP is produced from ADP

21 Krebs Cycle Figure 2.5 (next slide) CoA = coenzyme A FAD 2+, FADH, FADH 2 = flavin adenine dinucleotide GDP = guanine diphosphate GTP = guanine triphosphate NAD +, NADH = nicotinamide adenine dinucleotide

22 Figure 2.5

23 Electron Transport Chain CoQ = coenzyme Q 3 ATP for NADHs Cyt = cytochrome 2 ATP for FADH 2s

24 Using your books Design a lesson to explain how much ATP we would get from 1 glucose molecule Include net and gross ATP gains Include the points during glycolysis, Kreb s Cycle, and Electron Transport where we create or lose ATP Include points where NADH and FADH 2 are created Indicate what the final product of the ETC will be and why this is so

25 Table 2.1 could be 4; depends on shuttle system into mitochondria

26 Biological Energy Systems The Oxidative (Aerobic) System Fat Oxidation Triglycerides stored in fat cells can be broken down Releases free fatty acids from the fat cells into the blood Releases glycerol molecule, as well FFAs and glycerol circulate and enter muscle fibers Some free fatty acids come from intramuscular sources FFAs enter the mitochondria, are broken down, and form acetyl-coa and hydrogen protons Acetyl-CoA enters the Krebs cycle Hydrogen atoms are carried by NADH and FADH 2 to the electron transport chain

27 Table 2.2 2

28 Biological Energy Systems The Oxidative (Aerobic) System Protein Oxidation Not a significant source of energy for most activities The three SO Whats? Protein is broken down into amino acids, and the amino acids are typically converted into glucose Control of the Oxidative (Aerobic) System Isocitrate dehydrogenase is stimulated by ADP and inhibited by ATP The rate of the Krebs cycle is reduced if NAD + and FAD 2+ are not available in sufficient quantities to accept hydrogen The ETC is stimulated by ADP and inhibited by ATP

29 Metabolism of Fat, Carbohydrate, and Protein Fat & CHO share some common metabolic pathways Note that all are reduced to acetyl- CoA and enter the Krebs cycle

30 Biological Energy Systems Energy Production and Capacity Inverse relationship Energy system s maximum rate of ATP production (i.e., ATP produced per unit of time) Total amount of ATP it is capable of producing over a long period. Phosphagen energy system primarily supplies ATP for high-intensity activities of short duration Glycolytic l system for moderate- to high-intensity h i it activities of short to medium duration Oxidative system for low-intensity activities of long duration

31 Table 2.3

32 Table 2.4

33 The extent to which each of the three energy systems contributes to ATP production Depends primarily on the intensity of muscular activity Depends secondarily on the duration of activity At no time does any single energy system provide all of the ATP for an activity it Key Point

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35 Phosphagen Substrate Depletion & Repletion ATP-PCr system stores Can decrease markedly (50-70%) during the 1 st 5-30 seconds of high-intensity exercise Can be almost eliminated as a result of very intense exercise to exhaustion Postexercise phosphagen h repletion Complete resynthesis of ATP appears to occur within 3 to 5 minutes Complete PCr resynthesis can occur within 8 minutes.

36 Glycogen Depletion & Repletion Glycogen dependency is related to exercise intensity it At relative intensities of exercise above 60% of VO 2max, muscle glycogen becomes increasingly important Entire glycogen content of some muscle cells can become depleted d Repletion of muscle glycogen during recovery is related to postexercise CHO ingestion Repletion appears to be optimal if 0.7 to 3.0 g of CHO per kg of body weight is ingested every 2 hours following exercise

37 Importance of Possible Limiting Factors to po ta ce o oss b e t g acto s to Varying Exercise Intensities

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40 Metabolic Specificity of Training Selecting an energy system Appropriate exercise intensities Appropriate rest intervals Results in more productive exercise regimens

41 Metabolic Specificity of Training Interval Training Emphasizes bioenergetic adaptations Uses predetermined intervals of exercise and rest More training can be done at higher intensities Goal is for more efficient energy transfer within the metabolic pathways Problem: Difficult to establish definitive guidelines for choosing specific work-to- rest ratios

42 Estimates for Work-to-Rest Ratios

43 Why do we need to recover? What forces us to take a break at all? excess postexercise oxygen consumption (EPOC): Oxygen uptake above resting values used to restore the body to the preexercise condition; also called postexercise oxygen uptake, oxygen debt, or recovery O 2.

44 Low-Intensity, ty, Steady-State State Exercise Metabolism Recovery = 1:1-1:3 75% of maximal oxygen uptake (VO2max)

45 High-Intensity, ty, Non-Steady-State State Exercise Metabolism Recovery = 1:3-1:5 Exercise above VO 2max The required VO 2 here is the oxygen uptake needed if such an uptake were possible Because it is not possible, the oxygen deficit lasts for the duration of the exercise

46 Metabolic Specificity of Training Combination Training Adds aerobic endurance training to the training of anaerobic athletes Recovery relies primarily on aerobic mechanisms Helps to enhance recovery Potential problems May reduce anaerobic performance capabilities Can reduce the gain in: Muscle hypertrophy Maximum strength Speed- & power-related performance Is the reverse true?