Biological energy metabolism involves the synthesis and breakdown of adenosine triphosphate (ATP) to provide energy to do work. 3 energy systems are available.
ATP (adenosine triphosphate) is the immediate source of energy for muscle cells. ATP consists of three parts:
- three linked phosphates
Energy Metabolism: ATP Synthesis & Breakdown
During ATP synthesis, an anabolic reaction, the enzyme ATP synthase facilitates the assembly of this high-energy bond, energy is stored, and can be used to perform work when needed.
ADP + Pi —-ATP synthase—->ATP + H2O
(adenosine diphosphate + inorganic phosphate = ATP)
During ATP breakdown, a catabolic reaction, the enzyme ATPase facilitates the break-down of this high-energy bond, energy is released and can be used to do the work.
ATP —-ATPase—–> ADP + Pi + Energy
The 3 Energy Systems
Since muscle cells need ATP constantly and ATP storage in muscle cells is limited, muscle cells need to reproduce ATP, which can be accomplished via three metabolic pathways (energy systems):
- ATP-CP System (stored ATP usage & creatine phosphate breakdown): anaerobic pathway (no oxygen involved)
- Glycolysis (breakdown of glucose/glycogen): anaerobic pathway (no oxygen is directly involved)
- Oxidative Rephosphorylation (aerobic breakdown of glucose, fat, protein): aerobic pathway
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