1 Stage – Aerobic Glycolysis The same process happens – Glucose is broken down to Pyruvic Acid However: Because of the presence of Oxygen, reaction can proceed further – Lactic Acid is NOT produced Reaction takes place in Sarcoplasm Energy yield is sufficient to synthesise 2 molecules of ATP July 2011

Stage 2 – Krebs’ Cycle “Krebs’ Cycle” – Series of chemical reactions in the Mitrochondria that oxidises Acetyl coA to CO2 and Hydrogen atoms Pyruvic Acid produced in the first stage diffuses into the Mitochondria and is added to an enzyme called coenzyme A (CoA) to become Aceytol CoA Mitrochondria – powerhouse of muscle cell – central role in production of ATP Aceytol CoA can now enter the next phase: July 2011

beta-oxidation - Aceytol CoA Krebs Cycle ….cont Krebs cycle is now pathway for oxidation of Carbs AND Fats Fatty acids (formed from breakdown of triglycerides) are broken down within the sacroplasm – through process: beta-oxidation - Aceytol CoA This process ‘prepares’ fatty acid for entry into the Mitochondria The Krebs’ cycle consists of 8 enzyme-driven reactions that oxidise aceytol CoA to CO2 July 2011

Aceytol CoA combines with oxaloacetic acid to form Citric Acid The Krebs’ cycle consists of 8 enzyme-driven reactions (producing energy) Aceytol CoA combines with oxaloacetic acid to form Citric Acid Citric Acid is then changed into a number of different compounds (producing energy), which regenerated Oxaloacetic Acid The cycle then repeats itself H atoms (part of aceytol CoA) transferred to H carriers July 2011

During cycle 3 important things happen: 1. Carbon Dioxide is formed 2. Oxidation takes place – Hydrogen is removed – via ‘Hydrogen carriers’ (chemical) 3. Sufficient energy is released to synthesise 2 molecules of ATP Hydrogen carriers then enter the next stage of aerobic metabolism July 2011

Stage 3 – Electron Transport Chain Hydrogen atoms transported to the inner membranes of the mitochondria Electrons removed from the Hydrogen are passed along by electron carriers – combining with oxygen and Hydrogen ions to form Water High energy Carbon-hydrogen bonds are being broken down (glucose) to form: 1. Low energy Carbon-Oxygen bonds (CO2) Hydrogen-Oxygen bonds (water) And to release energy to compbine ADP and P to form ATP July 2011

Energy yield from ETC produces 34 molecules of ATP Total yield for of Aerobic respiration is 38 molecules of ATP The aerobic system of synthesising ATP is the most efficient: energy produced by products easily expelled from body These reactions do however rely on the availability of oxygen July 2011

Oxygen can be delivered at a rate to match Oxygen demand At the onset of exercise/during very intense exercise, the oxygen distributed to the cells is NOT enough for the body to rely on this system – as a method of replenishing ATP stores. During submaximal exercise, the aerobic system is the predominant method of ATP production: Oxygen can be delivered at a rate to match Oxygen demand Unless stores of Carbs, Fats and Proteins runs out – this system is unlimited. July 2011