Atp Resynthesis System

Resynthesis of ATP

• ATP breakdown and resythesis is a coupled reaction. (AKA a reversible reaction).                                   Coupled reaction – a chemical reaction in which energy is transferred from one side of the reaction to the other.

ATP         ADP + P + Energy (for muscle contraction)[pic 1]

ADP + P + Energy (for energy systems)                 ATP[pic 2]

• Resynthesis of ATP is done aerobically.
• The more intense the exercise, the more ATP is used to provide energy for the muscle contractions.
• Therefore, the more ATP we need to resythesise.

There are two anaerobic energy systems:

• The ATP-PC system (Phosphocreatine)
• The lactate anaerobic energy system

The ATP-PC system

Phosphocreatine (PC): an energy-rich compound of creatine and phosphoric acid, found in muscle cells.[pic 3]

   CP          C + P + ENERGY [pic 4]

ATP            P + ADP + ENERGY[pic 5]

• There is no oxygen involved so the process is entirely anaerobic.
• For every molecule of PC that is broken down, enough energy is released to resynthesize one molecule of ATP.
• A positive of this system is that the energy is released rapidly and allows for the rapid resynthesis of ATP that is necessary if the body is undertaking short bursts of maximal work (e.g sprinting).
• Another positive is that there are no waste products from the process.
• A disadvantage of the system is that stores of PC are limited, there is only enough for approx. 5-8 seconds of high-intensity work. The PC stores do get replenished but it can take up to 3 minutes to fully refuel.

The Lactate Anaerobic energy system

• Involves the partial breakdown of glucose.
• Hydrogen is released both during glycolysis (the breakdown of glucose to pyruvate) and during the complex chemical equations occurring during the Kerbs cycle.
• These hydrogen ions are combined with oxygen from respiration in the electron chain to form water.
• This process works well for low-intensity exercise, but more ATP must be resynthesized as the level of work increases and therefore more glucose is broken down and more hydrogen is transferred to the electron transport chain.
• More oxygen becomes available as the ventilation rate and cardiac output increase.
• The amount of oxygen that can be made available to and used by muscle cells is finite, it is known as VO2 max.