Energy SystemsGeorge Noorland

Energy

Concept Definition Measure/UnitsEnergy The capacity of the body to perform work/put mass into motion. Joules (J)Work The ability to apply force over s distance. Work = Force (N) x

Distance (m).Joules (J) or Newtons (N)

Power Work performed per unit of time/ the rate at which we can work. Watts (W)

The ATP/PC (Alactic) Energy System:Type of Reaction AnaerobicChemical/Food Fuel Phosphocreatine (PC)Site of Reaction Sarcoplasm (in muscle cells)Controlling Enzyme Creatine KinaseEnergy Yield 1 ATP (NOT EFFICIENT)By-Products None (because it is too quick)Duration Up to 10 seconds (3-8 seconds)Intensity High (maximal)

Adenosine Triphosphate (ATP):ATP- A chemical energy stored as a high energy compound in the body. It is the only immediately usable source of energy in the human body.

- Adenosine – P – P – P = ATP- It is stored as a simple compound in the muscles so that it can be quickly broken down to supply energy for

approximately 2-3 seconds of muscular work. - When broken down by the enzyme ATPase, it releases the potential energy stored in the muscles to apply force

as kinetic energy.

Types of Energy:Chemical Energy- Potential energy that is stored in chemical bonds of molecules, it is the part of energy in a substance that can be released by a chemical reaction. Kinetic Energy- Energy in the form of muscle contraction/ joint movement- extra energy that the body possesses because of its motion.

KE = ½ M x V² (Kinetic Energy = Half of the mass of an object multiplied by the velocity squared).Potential Energy- The energy possessed by an object because of its position (height above ground- field of gravity) - The energy is stored in the object until it moves.

ATP Re-synthesis:- The breakdown of ATP into ADP is reversible in an endothermic reaction. - This re-synthesis requires energy from one of the 3 energy systems.- The ATP/PC, lactic and aerobic energy systems work together to supply energy to re-synthesise ADP back into

ATP via coupled reactions.

Endothermic Reaction- A chemical reaction that requires energy.Exothermic Reaction- A chemical reaction that releases energy.Coupled Reaction- A reaction in which the product (energy) of one reaction is used by a second reaction. Threshold- The point at which there is a switch between from one predominant energy system to another.

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This system will keep going until PC levels drop, at this point you will then move over the threshold into the next system- Lactic Acid System. Phosphocreatrine (PC)- An energy-rich compound found in muscle cells that is used to recycle ATP during activities of very high intensity and short duration.

Advantages Disadvantages- There is no need for oxygen- anaerobic.- No fatiguing by-products. - PC stores in muscles are a readily available energy

source. - This system provides energy for high-intensity,

explosive exercise and movement. - PC can be re-synthesised quickly after activity

stops.- It is a relatively quick process- there are few

reactions.- Automatically stimulated by a decrease in ATP and

an increase in ADP.

- Only enough PC stores for 10 seconds- there is a limited supply of PC in muscles.

- Only 1 ATP is re-synthesised in this system (1 ATP for 1 PC).

- PC stores are only replenished with oxygen- during recovery when the exercise stops.

The Lactic Acid Energy System:Type of Reaction AnaerobicChemical/Food Fuel Glycogen/Glucose (carbohydrates)Site of Reaction Sarcoplasm (in muscle cells)Controlling Enzyme PFKEnergy Yield 2 ATP (NOT EFFICIENT)By-Products Lactic AcidDuration 10 seconds – 3 minutes (peak at 1 minute)Intensity High/medium

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Glycolysis- The breakdown of sugar.Lactic Acid- The by-product of anaerobic exercise produced by anaerobic glycolysis.

Advantages Disadvantages- There are large glycogen stores in the muscle/liver

which is readily available as a potential energy source.

- This system re-synthesises 2 ATP, which is more that the alactic system.

- This system requires fewer reactions that the aerobic system, so provides a quicker supply of energy.

- Lactic acid can be converted back to glycogen/ pyruvic acid.

- This system can be used to increase the intensity during exercise.

- This system is anaerobic- there is no need for oxygen.

- It provides energy for high-intensity exercise lasting between 10-180 seconds.

- This system is not as quick as the ATP/PC system.- Produces lactic acid, which is a fatiguing by-

product. - Reduces the pH (increased acidity) which inhibits

enzyme action. - Stimulates pain receptors. - Only 2 ATP are re-synthesised, this means that it is

not efficient.- To continue exercise, the intensity must be

lowered.

The Aerobic Energy System:Type of Reaction AerobicChemical/Food Fuel Glycogen/Glucose/Carbohydrates/FatsSite of Reaction Sarcoplasm (in muscle cells) and MitochondriaControlling Enzyme PFKEnergy Yield 34 ATP – 38 ATP (EFFICIENT)By-Products Water, CO2Duration Hours - ContinuousIntensity Low (sub-maximal)

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Advantages Disadvantages- There are large potential glycogen and free fatty

acid (FFA) stores available as an efficient energy store.

- Efficient ATP re-synthesis when good O₂ supply guarantees breakdown of FFAs.

- Large ATP re-synthesis: 38 ATP from one molecule of glucose compared to 2 ATP from the LA system and 1 from the ATP/PC.

- Provides energy for low/moderate-intensity and high-duration exercise (3 minutes – 1 hour).

- No fatiguing by-products; CO₂ and H₂O easily removed.

- Slower rate of ATP re-synthesis compared with the LA system due to:

- Requires more O₂ supply (15% more for FFAs).- More complex series of reactions.- Cannot re-synthesise ATP at the start of exercise

due to initial delay of O₂ from the cardiovascular system.

- Limited energy for ATP during high-intensity, short-duration work.