CHAPTER 21 ENERGY SYSTEMS and the RECOVERY PROCESS

Transcription

1 CHAPTER 21 ENERGY SYSTEMS and the RECOVERY PROCESS Text between pages 127 and 134 answers to questions on page 134 of the text book 1) Define energy, and briefly describe how energy is released from food in the body 5 marks 1 mark for definition: Energy is the capacity or ability to perform work for how energy is released from food in the body: Fuel foods are fuel stored in the body, the first is carbohydrate CHO (digested to glucose) The second type of fuel food consists of fats (digested to fatty acids and glycerol) These are used to create chemical energy in the form of adenosine triphosphate (ATP) This is an endothermic reaction (it takes in energy from the food and creates the ATP) This process is both aerobic and anaerobic, within all living tissue ATP is an immediate usable form of chemical energy for all body processes Including that used by skeletal muscle to perform mechanical work The usage of ATP to create energy is an exothermic reaction 2) a) Identify the only form of usable energy in the body 1 mark Adenosine Triphosphate (ATP) b) What is meant by an exothermic reaction? Illustrate this definition with an example Exothermic reaction is a reaction that releases energy For example: ATP è ADP + P i + energy c) What is meant by an endothermic reaction? Illustrate this definition with an example Endothermic reaction is a reaction that takes in energy For example: restoration of ATP from ADP Or ADP + P i + energy è ATP 3) a) An elite cyclist wants to discover her maximum output when sprinting A load of 85 newtons is applied to the wheel of a cycle ergometer The cyclist then sprints for 10 seconds and records a distance travelled of 200m Assuming that no other force is acting on the cycle, calculate the power output of the cyclist Show each stage of your calculation Work = force x distance moved = 85 x 200 = joules Power = energy (joules) = = 1700 watts time (sec) 10 b) Name the predominant energy system that would be utilised during this activity and describe how ATP is re-created within this system Alactic anaerobic energy system or the ATP-PC system ATP is resynthesised via phosphocreatine Coupled reaction between PC and ADP Or equation illustrating coupled reaction: enzyme creatine kinase Stage 1 PC è P i + C + energy Stage 2 Energy + ADP + P i è ATP + C Net effect of coupled reaction: PC + ADP è ATP + C 95

2 SECTION B OPTION B3 CHAPTER 21 ANSWERS TO QUESTIONS 4) a) An elite swimmer performs a flat-out 100 metre freestyle swim in 50 seconds Describe how most of the ATP is regenerated during the swim Via the lactic acid system Process called glycolysis or the incomplete breakdown of sugar Glycolytic enzymes (for example, phosphofructokinase PFK) assist breakdown of glucose Without oxygen being present figure Q211 variation in Takes place in the muscle cell sarcoplasm contribution of energy system One molecule of glucose is broken down to release 2ATP This is converted into pyruvic acid which is converted to lactic acid By enzyme lactate dehydrogenase (LHD) b) Sketch a graph, which shows the use of the appropriate energy systems against time during the swim See sketch graph figure Q211 The ATP store is used up after 2 seconds or less The ATP or PC system builds to a peak at 3 seconds and drops to zero after 9 seconds The lactacid system peaks at around 20 seconds and then drops to zero at around 50 seconds The aerobic system builds gradually from zero, always less than other system contributions 5) a) Taking part in a triathlon involves swimming, cycling and running Briefly describe how the aerobic energy system within the cell mitochondria supports this endurance event 6 marks 3 marks for: In the presence of oxygen In the cell mitochondria Oxaloacetic acid and acetyl coa combine to form citric acid To enter Kreb s cycle where pairs of hydrogen atoms are released CO 2 is formed 2ATPs are produced 3 marks for: Co-enzymes transport hydrogen atoms (ions and electrons) into the electron transport chain Hydrogen ions and electrons are charged with potential energy Which is released in a step-by-step manner As O 2 is delivered to react with the hydrogen ions and electrons To create a large energy yield per molecule of glucose (32 or 34 ATPs) and water % of maximum rate of energy production ATP store overall performance ATP-PC aerobic system 2s system ta d syste ac c l i 10 s m 50s time b) Construct a graph, which illustrates the food fuel usage against time during a triathlon race lasting 2 hours See figure Q212 1 mark for shape of carbohydrate curve 1 mark for shape of fat curve % of fuel food use figure Q212 food fuel usage during a triathlon fats CHO 2hrs time 96

3 6) Compare the relative efficiency of ATP production via the aerobic and anaerobic routes Explain your answer 3 marks The aerobic route is times more efficient than anaerobic route ATP molecules are produced aerobically per molecule of glucose Compared with 2 ATP molecules, produced anaerobically for one molecule of glucose Explanation: Anaerobic production of ATP is the incomplete breakdown of one molecule of glucose (glycolysis), therefore there is very limited ATP production Whereas the aerobic production of ATP completely breaks down the glucose molecule To release all potential energy (energy stored in the molecules) Hence a much higher energy yield 7) The diagram in figure 2115 is an energy continuum in relation to a variety of sports activities a) Explain the concept the energy continuum The energy continuum is a concept used to describe the type(s) of respiration And describes the shares of anaerobic and aerobic types of respiration Demanded by different types of physical activities (games or sports) b) At each end of the continuum examples of sporting activities have been omitted Give one example of a sporting activity that is predominantly anaerobic and one example of a sporting activity that is predominantly aerobic Anaerobic: 100m sprint, javelin throw, long jump, weight lift Aerobic: Marathon, jogging, long distance swimming, long distance cycling figure 2115 variation in contribution of energy system 100m swim boxing hockey rowing (2000m) 3000m run crosscountry run c) Suggest two factors that need to be considered in evaluating sports activities on the basis of their relative position on the energy continuum The total amount of ATP required during that activity Or power or rate at which ATP is required during the performance Intensity and duration of the exercise period d) Explain, using specific examples, why a game of hockey has aerobic and anaerobic components Skills in the game are largely anaerobic Example, short fast dribble stresses ATP-PC system Repetition back to back sprints stresses lactic acid system Playing duration normally exceeds 1 hour giving time for recovery for player in off the ball situations Production of ATP via the aerobic system aerobic anaerobic

4 SECTION B OPTION B3 CHAPTER 21 ANSWERS TO QUESTIONS 8) a) State where and in what conditions lactic acid is commonly found in relatively large amounts Conditions for lactic acid are anaerobic Lactic acid is found in (muscle cell) sarcoplasm b) There are several ways by which lactic acid can be removed from active muscles Identify the major pathway for the removal of lactic acid and the organs and tissues involved for: Lactic acid is converted back to pyruvic acid And the majority of lactate is oxidised within cell mitochondria - ie the aerobic energy system pathway for two of organs and tissues which are involved in the removal of lactic acid: Oxidation occurs in slow twitch muscle fibres (once sufficient O 2 is available) Blood transports lactic acid (for oxidation) to other organs, which have not been operating under anaerobic conditions Such as liver, kidneys, brain, heart c) How does light exercise influence lactate removal? 3 marks Light exercise keeps blood capillaries dilated Avoids blood pooling Flushing oxygenated blood through the muscle Increasing the oxidation of lactic acid and removing lactate from the muscle cells 9) Explain why cool-down is important within an exercise regime Cool-down: Continued low level exercise and stretching keeps the capillary beds open within active (muscle) tissue This avoids blood pooling (blood is stored in the venous system as a reservoir until muscle contractions force it back towards the heart) This enables the flushing out of waste products such as lactic acid from the metabolic processes Enabling the body s systems to gradually return to its resting state Which limits muscle soreness (DOMS) And enhances recovery from the exercise period 10) Figure 2116 shows oxygen uptake of an elite games player undertaking exercise followed by a recovery period a) Using the appropriate letters, identify the oxygen deficit and Excess Post Oxygen Consumption (EPOC) 3 marks Oxygen deficit = E EPOC = A and D b) Why does the elite player incur an oxygen deficit during exercise? The oxygen deficit represents the difference between the oxygen required during the exercise And the oxygen actually consumed during the activity resting O2 consumption exercise recovery c) Excess Post Oxygen Consumption (EPOC) is considered to have two components State two aims of the first component and explain how this component is achieved 1 mark for one of: The first component is called the alactacid component and involves the restoration of muscle phosphagen So that exercise can begin again within 3 minutes of recovery time 3 marks for explanation: This component involves the conversion of ADP back to PC and ATP Firstly, there is aerobic conversion of carbohydrates into CO 2 and H 2 O to resynthesise ATP from ADP and P i Then some of the ATP is immediately utilised to create PC using the coupled reaction: ATP + C è ADP + PC VO 2 rest figure 2116 oxygen consumption during exercise and recovery E C A D B time 98

5 d) Describe the process of ATP production that restores the oxygen debt or EPOC 6 marks Description or equivalent diagram: Stage 1 = glycolysis in sarcoplasm Energy yield 2ATPs per molecule of glucose Stage 2 = Kreb s cycle in cell mitochondria In presence of oxygen (O 2 ) Yields 2ATPs per molecule of glucose And carbon dioxide (CO 2 ) Releases H + and e - into next stage Stage 3 = Electron transport stage In inner cristae of mitochondria Oxygen used to create ATP as H + and e - meet With water (H 2 0) given off Creates 32 or 34 ATPs per molecule of glucose 11) An elite games player performs an interval training session during which the rate of muscle phosphagen levels during the recovery period was recorded The results from this training session are given in table 213 a) Using the results in table 213, plot a graph of recovery time against the percentage of muscle phosphagen restored 3 marks Table 213 muscle phosphagen during recovery See figure Q213 recovery time (s) muscle phosphagen restored (%) % b) What resting value would you recommend for a full recovery, and what would be the effect of restarting the exercise after 30 seconds? 1 mark for resting value: seconds needed for full recovery 1 mark for the effect of restarting exercise: 50% of muscle phosphagen would have been restored Or 50% muscle phosphagen would have been depleted c) Part of the recovery mechanism after anaerobic exercise involves myoglobin Explain the function of myoglobin during the recovery process 3 marks Myoglobin is an iron protein molecule located within skeletal muscle Structure is similar to haemoglobin Myoglobin facilitates transportation of O 2 from HbO 2 Into the muscle cell or the mitochondria It acts as a temporary storage site for O 2 % muscle phosphagen restored 100% 80% 60% 40% 20% figure Q213 phosphagen recovery recovery time / s 99

6 SECTION B OPTION B3 CHAPTER 21 ANSWERS TO QUESTIONS 12) How could information on oxygen debt recovery be of use to an athlete and coach in designing training sessions? 6 marks for two of general comments on recovery: The intensity and duration of an exercise period will determine the recovery or rest relief needed between repetitions/sets and training sessions This concept is known as the work-rest relief ratio When planning training sessions, rates of recovery must be take into account Recovery between bouts of exercise is dependent on heart rate values As heart rate (HR) falls during recovery, its value is a measure of alactacid/lactacid recovery Therefore repeating an exercise bout may not be possible until HR has fallen by a certain amount for two of: The alactacid recovery component is quick ie within 3 minutes And so it is possible to do many short, fast repetitions within a short period of time And repeat high quality sessions within a short period of time For example, a typical speed training session: 2 sets (6 x 60m sprints at 100%) 3 minutes recovery between repetitions, 8 minutes recovery between sets for two of: The lactacid component of recovery is a much slower process Hence the rest relief ratio is much greater For example, a typical 400m athlete s summer training session: 2 sets (2 x 300m sprints at 90%) 15 minutes recovery between repetitions, 20 minutes recovery between sets Active recovery or cool-down speeds up removal of lactic acid Variance in the intensity of workload in sessions is important, so that the lactic acid system is not stressed in every session And so reducing the training intensity will give a recovery time between lactacid training sessions 13) Physical activity by far provides the greatest demand for energy Discuss how the intensity and duration of the exercise period and the relative contributions of the body s means for energy transfer affect performance In your answer mention availability of O 2, food fuels used, energy threshold points, enzyme control and how the fitness of the participant affect performance 20 marks Note you will need to refer to content in both chapters 22 and 23 to answer this question 1 mark for introduction of topic: The major energy pathway for ATP production differs depending on the intensity and duration of the exercise 3 marks for brief description and application of the ATP-PC energy system: In intense exercise of short duration, for example 100m sprint, the energy is derived from the already present stores of intramuscular ATP and PC stores otherwise called the ATP-PC system This is an immediate energy system It does not require oxygen And is controlled by the enzyme creatine kinase 5 marks for brief description and application of the lactic acid energy system: For intense exercise of longer duration (15 seconds-2 minutes) energy is generated mainly form the anaerobic reactions of glycolysis or lactic acid system - again a short-term energy system Carbohydrate from the food a person has eaten is stored as glycogen and converted to glucose It is the incomplete breakdown of glucose, assisted by enzymes such as glycogen phosphorylase, which provides the limited energy released during glycolysis Since there is no oxygen present, the end product of this reaction is lactic acid The enzyme facilitating the conversion from pyruvic acid to lactic acid is lactate dehydrogenase (LDH) 100

7 Peak power output is a measure which represents the highest power generated during any 3-5 second period of maximum exercise The fitter the person the quicker and greater the power output Power trained athletes have a higher percentage of fast twitch muscle fibres, when compared with untrained people Resulting from hypertrophy and hyperplasia of fast twitch muscle fibres Hence power athletes have increased muscle cell stores of substances such as ATP, PC and glycogen And increase in anaerobic enzymes such as creatine kinase And improved toleration to lactate acid And improved ability to remove lactate acid from muscle cells into blood Thus enhancing the ATP-PC-lactate threshold and lactate-aerobic threshold And reducing the delayed onset of muscle soreness (DOMS) Therefore the bigger the anaerobic capacity the better the anaerobic performance Producing amazing performances such as those witnessed by the Global superstar sprinter Usain Bolt in the Beijing Olympic Games 5 marks for brief description and application of the aerobic acid energy system: As exercise progresses into several minutes, the aerobic system predominates and oxygen consumption becomes an important factor Assisted by aerobic enzymes such as glycogen phosphorylase needed for the breakdown of glucose during glycolysis And lipoprotein lipase needed for the breakdown of fats within Kreb s cycle The longer the exercise period, the more the performer reaches a steady rate of oxygen uptake Representing a balance between the energy requirements of the working muscles and the aerobic resynthesis of ATP The aerobic system depends on CHO in the form of glucose, derived from glycogen stores in mainly slow twitch muscle fibres After approximately 30 minutes fats (FFAs) begin to contribute towards energy production by a process called B-oxidation A high CHO diet would assist replenishment of glycogen stores And therefore sustain endurance running times in events such as marathons and the energy levels of a group of walkers on a full day s mountain walk During prolonged exercise endurance athletes utilise FFAs sooner that untrained people This training adaptation enables the trained athlete to not use glycogen up immediately, but save it for later on in an exercise effort or when the intensity of the exercise increases This training adaptation is called glycogen sparing 5 marks for brief description and application of the aerobic capacity: The maximum capacity for aerobic resynthesis of ATP is measured as the maximum oxygen consumption of V O 2max This is one of the important indicators of one s ability for sustained exercise As work intensity increases, lactic acid starts to accumulate above resting values The onset of blood lactate accumulation (OBLA) represents a point where the production of lactate exceeds the speed of its removal And is characterised by muscle fatigue, pain and deterioration of physical performance OBLA can be expressed as a percentage of V O 2max Hence, trained athletes begin OBLA at higher work intensities (85-90% of their V O 2max ) compared with untrained athletes (50-55% of their V O 2max ) Which means for the trained endurance athlete, the lactic-aerobic threshold moves to higher values of V O 2max And therefore an endurance-trained athlete is capable of a better endurance performances For example, cross-country skiers have very high V O 2max values needed to sustain a very demanding physical activity 1 mark for summary: The fitter a person is the greater the intensity and duration of the exercise period a person can work towards This is because the human body physiologically adapts as a natural response to long-term training 101