The ATP-PC system

this system kicks in during high intensity activity after the first 2 seconds of intense activity depletes the original ATP stores.

ATP levels falls and ADP and P stores rise → triggers the release of creatine kinase (an enzyme which catalyses the breakdown of phosphocreatine (PC))

phosphocreatine is a high-energy compound stored in the muscle cell and broken down for ATP resynthesis. the food fuel used for the ATP-PC system. PC is broken down anaerobically (without the presence of oxygen) in the sarcoplasm. the high-energy bond between the creatine and phosphate is broken, releasing energy for ATP resynthesis → used for muscular contraction

  • for every one mole of PC broken down, one mole of ATP can be resynthesised

this forms a coupled reaction; the products of one reaction are used in another reaction

the exothermic (releases energy) reaction of breakdown of PC:

  • PC → P + C +Energy

the endothermic (absorbs energy) reaction of ATP resynthesis:

  • Energy + ADP + P → ATP

Pros of the ATP-PC System:

  1. Immediate Energy: Provides quick energy for high-intensity activities. no delay for oxygen

  2. No Oxygen Required: Works anaerobically, without the need for oxygen.

  3. Efficient for Short Bursts: Ideal for short, explosive movements like sprinting (100m sprint) or weightlifting.

  4. No fatiguing by-products: aids fast recovery

Cons of the ATP-PC System:

  1. Limited Energy: Stores are small and quickly depleted, providing energy for only 8-10 seconds.

  2. Recovery Time: Takes time to replenish ATP-PC stores after depletion.

  3. Not Sustainable: Not suitable for prolonged activities due to rapid exhaustion.