1.1c energy for exercise

    Cards (60)

    • energy is the capacity to perform work and can exist in chemical, potential and kinetic forms. chemical energy held in the food we eat can be stored as potential energy in the body tissues and converted into kinetic energy as we contract our muscles. maximising this process is essential to improve training and performance
    • adenosine triphosphate (ATP)
      a high energy compound which is the only immediately available source of energy available source of energy for muscular contraction
    • metabolism
      the chemical processes that occur within a cell to maintain life. some substances are broken down to provide energy while others are resynthesised to store energy
    • ATP breakdown
      for the exercising body, ATP is stored in the muscle cell and is the only immediately available source of energy for muscular contraction. it is made up of one adenosine and three phosphates held together by bonds of chemical energy. to extract the energy from ATP, the enzyme ATPase is released, which stimulates the final high energy bond to be broken. this exothermic reaction releases energy for muscular contraction and leaves adenosine diphosphate (ADP) and a single phosphate (P)
    • ATPase
      an enzyme which catalyses the breakdown of ATP
    • exothermic reaction
      a chemical reaction which releases energy
    • adenosine diphosphate (ADP)
      a compound formed by the removal of a phosphate bond from ATP (ATP --> ADP + P + energy)
    • ATP resynthesis
      the store of ATP in the muscle cell is exhausted quickly, lasting only 2-3 seconds: several powerful contractions or several seconds of sprinting. in order to continue exercising, ATP must be constantly resynthesised or rebuilt. to do this, and endothermic reaction occurs where energy from the surrounding area is absorbed to rebuild the high energy bond between ADP and a single phosphate (P). the energy required is provided by one of three energy systems which break down food fuels stored around the body
    • endothermic reaction
      a chemical reaction which absorbs energy
    • energy systems
      there are three energy systems which break down food fuels to provide the energy for ATP resynthesis
      1. ATP-PC
      2. glycolytic
      3. aerobic
      at any one time, depending on the intensity and duration of the activity, one energy system will dominate to maintain ATP resynthesis. ATP will then be continuously broken down to provide energy for muscular contraction for the duration of the activity. if ATP fails to be resynthesised, there will be no energy released for muscular contraction and fatigue will quickly set in
    • the ATP-PC system
      the ATP-PC system resynthesises ATP from the breakdown of phosphocreatine (PC) by creatine kinase in a coupled reaction
      • PC --> C + P + energy in an anaerobic reaction in the sarcoplasm yielding one mole of ATP, for very high intensity activities lasting 2-10 seconds
    • creatine kinase
      an enzyme which catalyses the breakdown of phosphocreatine (PC)
    • anaerobic
      without the presence of oxygen
    • sarcoplasm
      the cytoplasm or fluid within the muscle cell which holds stores of PC, glycogen and myoglobin
    • coupled reaction
      where the products of one reaction are used in another reaction
    • an example of an activity which uses the ATP-PC system is throwing a javelin in athletics
    • AO3: ATP-PC system
      strengths
      • no delay for oxygen
      • PC readily available in the muscle cell
      • simple and rapid breakdown of PC and resynthesis of ATP
      • provides energy for very high intensity activities
      • no fatiguing by products and simple compounds aid fast recovery
      weaknesses
      • low ATP yield and small PC stores lead to rapid fatigue after 8-10 seconds
    • the glycolytic system
      the glycolytic energy system resynthesises ATP from the breakdown of glycogen by GPP and glucose by PFK
      • glucose --> pyruvic acid + energy in the sarcoplasm yielding two moles of ATP, for high intensity activities lasting 10 seconds to three minutes
      • pyruvic acid --> lactic acid by LDH due to anaerobic conditions which accumulates to reach OBLA, causing fatigue
    • phosphofructokinase (PFK) 

      an enzyme which catalyses the breakdown of glucose (glycolysis)
    • anaerobic glycolysis
      the partial breakdown of glucose into pyruvic acid
    • lactate dehydrogenase (LDH)
      an enzyme which catalyses the conversion of pyruvic acid into lactic acid
    • AO3: glycolytic system
      strengths
      • no delay for oxygen and large fuel stores in the liver, muscles and blood stream
      • relatively fast fuel breakdown for ATP resynthesis
      • provides energy for high intensity activities for up to three minutes
      • lactic acid can be recycled into fuel for further energy production
      weaknesses
      • fatiguing by product lactic acid reduces pH and enzyme activity
      • relatively low ATP yield (1:2) and recovery can be long
    • aerobic system
      the aerobic system kicks in during low to moderate intensity activity as the arrival of sufficient oxygen enables continued energy production. the aerobic system contains three stages:
      1. aerobic glycolysis
      2. kreb's cycle
      3. electron transport chain (ETC)
    • aerobic glycolysis
      aerobic glycolysis in the sarcoplasm converts glucose into pyruvic acid with the enzyme PFK catalysing the reaction. this releases enough energy to resynthesise 2 molecules of ATP. converting glycogen into glucose (by enzyme GPP) maintains process for extended periods of time. as oxygen is now in sufficient supply the pyruvic acid is no longer converted into lactic acid. it goes through a link reaction catalysed by coenzyme A, which produces acetyl CoA. this allows access to the mitochondria.
    • Kreb's cycle
      Acetyl CoA combines with oxaloacetic acid to form citric acid, which is oxidised through a cycle of reactions. known as the kreb's cycle, CO2, hydrogen and enough energy to resynthesise two molecules of ATP are released. this process occurs in the matrix (intracellular fluid) of the mitochondria
    • electron transport chain (ETC)
      the hydrogen atoms are carried through the ETC along the cristae (folds of the inner membrane) of the mitochondria by NAD and FAD (hydrogen carriers), splitting into ions (H+) and electrons (H-). hydrogen ions are oxidised and removed as H2O. pairs of hyrogen electrons carried by NAD release enough energy to resynthesise 30 moles of ATP and those carried by FAD release enough to resynthesise 4 moles of ATP. the overall yield of the ETC is 34 moles of ATP
    • an example of an activity that uses the glycolytic energy system is a 200m sprint
    • an example of an activity that uses the aerobic energy system is a marathon
    • lipase
      an enzyme which catalyses the breakdown of triglycerides into free fatty acids (FFAs) and glycerol
    • AO3: aerobic system

      strengths
      • large fuel stores: triglycerides, FFAs, glycogen and glucose
      • high ATP yield and long duration of energy production
      • no fatiguing by products
      weaknesses
      • delay for oxygen delivery and complex series of reactions
      • slow energy production limits activity to sub-maximal intensity
      • triglycerides or FFAs demand around 15 per cent more O2 for breakdown
    • energy continuum
      the relative contribution of each energy system to overall energy production depending on intensity and duration of the activity
    • intensity very high: duration <10 seconds
      in individual activities such as athletic jumps, throws and sprints, where the intensity is very high and duration is 2-10 seconds, the ATP-PC system will be predominant, contributing up to 99 percent of energy for ATP resynthesis
    • intensity high: duration 10 seconds to 3 minutes
      in individual activities such as the 400m, 200m freestyle ad a competitive squash game where the intensity is high and duration is between ten seconds and three minutes, the glycolytic system will be predominant, contributing 60-90 per cent of the energy for ATP resynthesis
    • intensity low to moderate: duration >3 minutes
      in individual activities such as marathons, triathlons and skiing, where the intensity is moderate but relatively constant for a significant duration, the aerobic energy system will be predominant, contributing up to 99 per cent of energy for ATP resynthesis
    • intermittent exercise
      where the activities intensity alternates, either during interval training between work and relief intervals or during a game with breaks of play or changes in intensity. e.g., a rugby player is required to alternate between various modes of activity such as standing, walking , sprinting, tackling and jumping. performing intermittent exercise is more energy demanding than continuous exercise when the running speed is the same, which places games players in a unique situation, with varying physiological demands as they switch from one energy system predominance to another
    • threshold
      the point at which an athlete's predominant energy production moves from one energy system to another
    • ATP-PC / glycolytic threshold
      as a wing attack in netball hears the whistle, they will sprint out to receive the centre pass over 3-4 seconds using the ATP-PC system. however, losing possession leads them to man-man mark for a period of time of up to one minute to regain possession. the PC stores quickly deplete and the glycolytic system takes over predominant energy production
    • glycolytic / aerobic threshold
      after the counter attack in netball results in a goal being scored, the player jogs back into position ready for the next centre to be taken . the intensity is significantly reduced and there is sufficient oxygen available for the aerobic system to take over to provide most of the energy for ATP resynthesis
    • additional factors which will affect the relative contribution of energy systems to overall energy production, for a games player
      • position of the player: for example, a goalkeepers aerobic energy system may be predominant with a small percentage from the ATP-PC system for very high intensity dives, kicks and defensive plays, whereas a central midfielders aerobic system will be required to jog back into position and track play, their glycolytic system will be used for counter attacks and set pieces and the ATP-PC system for high intensity shots or tackles
    • additional factors which will affect the relative contribution of energy systems to overall energy production, for a games player
      • tactics and strategies used: for example, man-man marking will raise the intensity compared with zonal marking and will require a larger contribution from the anaerobic energy systems
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