The triathlon is an athletic event that involves performers undertaking a long distance swim, immediately followed by a cycle race and then finally a run of several kilometres.   (a) What would be the major energy sources used by a triathlete? (3 marks) (b) Briefly explain how these energy sources are used for regeneration of ATP. (5 marks)

2 (a) 1. Fats; 2. Fatty acids; 3. Glycerol; 4. Triglycerides. Sub max 2 marks 5. Carbohydrates; 6. Glycogen; 7. Glucose; 8. Protein/lactate. Sub max 2 marks 3 marks

(b) 1. Carbohydrates/glycogen/glucose broken down into pyruvate; 2. Anaerobic/glycolysis; 3. Some ATP produced; 4. Fats/triglycerides/fatty acids/glycerol broken down into variety of compounds; 5. Beta oxidation; 6. Into mitochondria; 7. Krebs cycle; 8. Electron transport chain; 9. Oxidation/aerobic; 10. Large quantities of ATP produced. 5 marks

What happens when we need energy quickly?

Anaerobic Respiration Describe how ATP is produced in the ATP-PC, and Lactic Acid systems Give advantages and drawbacks of these systems.

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Anaerobic Respiration Does not require the presence of oxygen! There are two types of anaerobic respiration: ATP-PC system (alactic system) Lactic Acid (Lactate anaerobic) system O2 O2 O2

Quick Recap – what happens in Glycolysis? Lactic Acid System Quick Recap – what happens in Glycolysis?

Glyco = Glucose Lysis = Splitting Glycolysis Glyco = Glucose Lysis = Splitting Occurs in the cytoplasm Glucose is converted into Glucose–6–Phosphate Enzyme involved = PFK (phosphofructokinase) Glucose–6–Phosphate is oxidised by the removal of 2 H2 molecules Glucose-6-Phosphate is split into 2 molecules of Pyruvate Energy is released and used to form 2 x ATP molecules

Lactic Acid System The Lactic Acid system is essentially the process of glycolysis. Occurs in the cell cytoplasm, Glucose is split into 2 x pyruvate molecules 2x ATP molecules are produced In aerobic respiration the pyruvate is then converted into Acetyl Co A by pyruvate dehydrogenase, and this enters Krebs Cycle.

When exercise intensity is high, oxygen supply to the muscles does not meet the demands for energy production. With insufficient oxygen, not all the pyruvate can enter Krebs Cycle, so some builds up in the cytoplasm If too much puruvate builds up, the process of glycolysis will stop and no more ATP will be produced. Instead, the enzyme lactate dehydrogenase converts the pyruvate to lactic acid This keeps glycolysis going so that 2x ATP can still be produced for each glucose broken down.

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Lactic Acid System Advantages Much faster to release energy than aerobic respiration Does not require oxygen so can occur during very high intensity exercise Any lactic acid produced can be converted back into glycogen and stored, or into pyruvate and used for aerobic respiration once exercise has finished Produced 2 ATP per glucose Muscles ability to buffer changes in pH can be improved by training

Lactic Acid System Disadvantages Lactic acid accumulates which lowers the pH of the muscle cell and blood, and can prevent glycolytic enzymes working Due to lactic acid build up, the muscles will fatigue within 1-3 mins Only releases 2 ATP compared to the 38 released by aerobic respiration – only 5% of the energy in each glucose can be harnessed.

Remember though before all this takes place we are able to able to obtain energy for short bursts (1-10 seconds) through the……………………………………………

ATP-PC (alactic) System Phosphocreatine (PCr) is an energy-rich compound found in cells. The breakdown of PCr releases enough energy to resynthesise 1 ATP Occurs in cell cytoplasm Enzyme involved = creatine kinase Muscles can contain stores of PCr sufficient to sustain around 10seconds of maximal exercise There is some evidence that creatine supplements can increase muscle PCr stores.

ATP-PC (alactic) System Advantages Very quick to provide energy to resynthesise ATP (almost immediate) Can sustain 10s intense exercise No fatiguing by-products produced PCr stores are recovered by aerobic respiration very quickly after exercise finishes (within 2-3 mins) Anaerobic – does not rely on oxygen supply PCr levels can be improved by training and supplementation

ATP-PC System Disadvantages Only lasts for 8-10s When PCr stores depleted they cannot be replenished until after exercise finishes, or if exercise intensity drops significantly (as high levels of O2 availability are required for aerobic respiration) – fatigue occurs. If exercise continues after the depletion of the PCr stores then other energy systems must be used to resynthesise ATP. Only 1 ATP resynthesised for every PCr broken down. Creatine supplementation has limited success, and potential side effects of cramps, bloating and dehydration.

The Energy Continuum The energy systems are not used one at a time – all three are continually being used together, but depending on the activity some may be used more than others. The factors that determine the predominant system: Availability of oxygen Exercise intensity How soon energy is required

The relationship between the 3 systems can be shown graphically: Aerobic Time 10s 1 min 3 mins ATP-PC Lactic Acid % Energy Supplied ATP-PC-LA Threshold LA-O2 Threshold

Activities lasting over 3mins Activities can be plotted along an energy continuum line to show the predominant energy systems being used: Activities lasting 2-10s Activities lasting over 3mins Anaerobic Aerobic ATP ATP - PC Activities lasting 10s-3mins Activities lasting 1-3s

Exam Questions: Elite swimmers can complete a 200 metres free-style race in just under 2 minutes. (a) (i) Describe how the majority of energy will be produced for this type of race. (4 marks) (ii) Explain the main cause of muscle fatigue during this type of race. (2 marks)

One popular form of training for Rugby Union is intermittent or interval training. This involves periods of intense exercise broken up with periods of rest. The graph shows levels of ATP-PC stores during a period of interval training. The player sprints 50 metres and then walks back to the start of the sprint to recover before repeating the sprint. (b) Use the graph to describe and explain the effects of interval training on ATP-PC levels. (4 marks)