1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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