Aerobic system of energy production needs oxygen At onset of activity, although oxygen is present in the muscles there isn’t enough to break down fuels into energy. So for immediate energy production the anaerobic systems are used ie ATP-PC system Lactic Acid System As soon as we start to exercise heart rate and breathing rate increases so more oxygen is getting to the muscles. Within a few minutes the muscles are supplied with enough oxygen for aerobic respiration to work.
Aerobic energy is used for low to moderate intensity and long duration. It offers a high energy yield, allowing activity to be maintained for long periods.
Elite athletes may use their aerobic pathways to perform what would be high intensity to lesser athletes.
Aerobic System uses oxygen to break down food fuels. This gives off a high energy yield. Carbohydrates and fats
Three stages of the aerobic pathway Stage 1 : Glycolysis Stage 2 : Kreb’s Cycle Stage 3 : Electron Transport Chain
Stage 1 glycolysis Glycogen Pyruvic Acid (pyruvate) Glycolysis P P ENERGY ADENOSINE P P ADENOSINE P P
As oxygen is present the pyruvic acid is NOT converted into lactate. Instead it is converted into acetyl-coenzyme-A (CoA) Acetyl Co-A moves to the mitochondria within the muscle cell where energy release now takes place.
Stage 2 Kreb’s Cycle Takes place inside the matrix of mitochondria. As Acetyl CoA enters the matrix it triggers a complex cycle of reactions called Kreb’s Cycle. From these reactions energy is produced to resynthesise 2 molecules of ATP. carbon dioxide is formed. hydrogen is taken to the electron transport chain.
Stage 3 electron transport chain Hydrogen is carried to the electron transport chain. This occurs in the cristae of the mitochondria. Hydrogen splits into hydrogen ions and electrons. Hydrogen ions are oxidised to form water. Hydrogen electrons provide energy for resynthesis of ATP (34 molecules)
Total energy yield from the aerobic system is 38 molecules of ATP
The aerobic system is the most efficient in energy production. The by-products (water and carbon dioxide) are easily expelled. The system relies on the availability of oxygen. However…
Sub-maximal exercise will predominantly use this system as oxygen can be delivered at a rate to match the demand for oxygen
Unless the body runs out of carbohydrate and fat stores, this system is unlimited.
summary Stage 1 Glycolysis (Sarcoplasm) Stage 2 Kreb’s Cycle (Mitochondria) Stage 3 Electron Transport Chain (Mitochondria) Glycogen Pyruvic Acid Acetyl Coenzyme A Acetyl Coenzyme A Carbon Dioxide Hydrogen Hydrogen Water 34 ENERGY ADENOSINE P P ADENOSINE P P P P ADENOSINE P P ADENOSINE P P P P ENERGY ADENOSINE P P P ENERGY
Glycogen Pyruvic Acid Acetyl Coenzyme A Carbon Dioxide Electron Transport Chain Glycolysis Water Oxygen present Hydrogen 2ATP 2ATP 34ATP Krebs Cycle
Fats can also be broken down to produce energy to resynthesise ATP
Triglycerides (stored fat in muscle) Glycerol and Fatty Acids Beta Oxidation Lipase Carbon Dioxide Electron Transport Chain Water Acetyl Coenzyme A Hydrogen Energy 130 ATP Kreb’s Cycle
Lots more ATP can be resynthesised (38 moles of ATP from 1 mole of glycogen). The body has large stores of muscle glycogen and triglycerides so exercise can last for several hours. Oxidation of glycogen and fatty acids do not produce any fatiguing by products. Advantages of the aerobic system
Takes a while for sufficient oxygen to be available to breakdown glycogen and triglycerides. Therefore this system cannot provide energy for ATP resynthesis straight away or during high intensity activity. disAdvantages of the aerobic system
How can this system be improved? Increased muscle stores of glycogen & triglycerides. Increased number of oxidative enzymes. Continuous training Fartlek training
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. What would be the major energy sources used by a triathlete? (3 marks) Briefly explain how these energy sources are used for regeneration of ATP. (5 marks)
Fats Fatty acids Glycerol Triglycerides (sub max 2 marks) Carbohydrates Glycogen Glucose (sub max 2 marks) What would be the major energy sources used by a triathlete? (3 marks)
Briefly explain how these energy sources are used for regeneration of ATP. (5 marks) Carbohydrates/glycogen broken down into glucose then into pyruvate. Called glycolysis. Some ATP is produced. In presence of oxygen, pyruvic acid converted into acetyl coenzyme A. Enters mitochondria where Kreb’s cycle takes place. Carbon dioxide and energy produced to resynthesise 2 molecules of ATP. Hydrogen is carried to electron transport chain. Water produced and energy to resynthesise 34ATP.
Considers the importance of each energy system in a particular activity. Intensity and duration will decide which energy system is used. Often there will be a combination of all three. Energy continuum
Energy continuum Example: Marathon Runner ATP-PC System – Start of race. Aerobic System – Majority of race. Lactate Anaerobic System – Sprint finish.
Example: Midfield in football ATP-PC System – Sprinting for the ball. Lactate Anaerobic System – High intensity work, chasing ball, moving into space, dribbling with ball. Aerobic System – Less intense periods when play does not involve the player. Time to recover using aerobic system.
Energy supplied against time A = ATP-PC - Lactic Acid threshold . The point at which ATP-PC system is exhausted and the lactic acid system takes over. B = Lactic Acid - Aerobic threshold . The point at which the lactic acid system is exhausted and the aerobic system takes over. ATP-PC Lactic Acid Aerobic
Phosphocreatine broken down by creatine kinase. Energy released is used to resynthesise ATP. Aerobic system used for recovery.
i) ATP-PC stores are exhausted rapidly in high intensity/short duration activities. 8-9 secs in average individual ii) Possible to achieve regeneration by up to 50% after 30 seconds rest iii) Can regenerate in game by walking or standing but supplies only go back up to approx 90% then down then back up to approx 80% then down etc.
At low intensity, the aerobic system is used. Fats, glycogen and carbohydrates broken down. Acetyl Coenzyme-A enters Kreb’s cycle in mitochondria. Carbon dioxide produced and a small amount of energy to resynthesise ATP. Hydrogen taken to electron transport chain. Lots of energy given off. As intensity increases, there will be a lack of oxygen. So ATP produced through lactic acid system. Glycogen broken down into pyruvic acid giving off energy to resynthesise ATP. As no oxygen present pyruvic acid converted to lactate.
In part (d)(ii), a disappointingly large proportion of candidates suggested that the energy systems somehow work in a sequence suggested by interpreting the x-axis of Figure 3 as simply duration of a single event, rather than as duration of differing events. Better answers, though rarer, did manage to suggest that a long-distance run was predominantly an aerobic activity, which became anaerobic as the intensity increased.
RATE OF ENERGY PRODUCTION % OF MAXIMUM RATE OF ENERGY PRODUCTION TIME 2 SECS 10 SECS 60 SECS 2 HOURS OVERALL PERFORMANCE ATP-PC SYSTEM LACTACID SYSTEM ATP STORE AEROBIC SYSTEM