Energy Systems
Energy
-
Is the capacity to do work (measured in joules)
Work = force X distance moved
Chemical Energy
Energy that is produced by a complex series of chemical reactions which can then
be made available as mechanical energy
Kinetic Energy
Energy due to movement which can be caused by muscular contraction
Potential Energy
Stored energy due to gravity
ATP
Adenosine Triphosphate = Adenosine + Phosphate + Phosphate + Phosphate
The energy currency of the body
There is 1 molecule of ATP stored in the body.
When we start to exercise an exothermic reaction (give out energy) using the
enzyme ATPase breaks down ATP to ADP (adenosine Diphosphate) + Pi + energy.
This reaction releases energy which causes muscles to contract.
This supplies the body with roughly 2 seconds worth of energy during maximum
work.
ATP/PC or Phosphocreatine or Creatine Phosphate Energy System
Anaerobic energy system
High intensity maximum work
Lasts 3-10 seconds
A coupled reaction takes place where PC (phosphocreatine) in a two stage process
is used to recreate ATP once it has been broken down into ADP + Pi.
Stage 1
Stage 2
PC  Pi + C + energy
energy + ADP + PiATP
This takes place in the muscle sarcoplasm.
Think 100m
Lactic Acid Energy System
The lactic acid energy system occurs during glycolysis in the muscle sarcoplasm. It
is anaerobic
During high intensity exercise this system becomes dominant between 10 – 60
seconds.
Glycolytic enzymes (phosphorylase (GPP), phosphofructokinase (PFK), lactate
dehydrogenase (LDH)) enable the breakdown of glucose to provide energy to
recreater ATP from ADP and Pi from glycogen
ADP + Glucose = ATP
Has a waste product called pyruvic acid
If not enough oxygen is breathed in to break pyruvic acid down (oxygen debt) it
converts into lactic acid
Think 400m
Aerobic Energy System
The aerobic system relies on the presence of oxygen to break down carbon dioxide,
water and energy. The energy yield is high; this is suitable for long term low intensity
exercise
Stage 1 = glycolysis in sarcoplasm (same as lactic acid energy system) – yields 2
ATP and hydrogen atoms.
Stage 2 = Kreb’s cycle in cell mitochondria, as there is oxygen present. Chemical
reactions occur in the cell mitochondria
Yields 2 ATP (per molecule of glucose) and carbon dioxide and releases Hydrogen
atoms and electrons
Fatty acids (acting as enzyme lipoprotein lipase) enter at this point.
Stage 3 = electron transport chain in the mitochondria creates 34 molecules of ATP
per molecule of glucose. Oxygen is given off from the muscle myoglobin is taken in
by the mitochondria to be used to oxidise hydrogen atoms.
H
(hydrogen atom)

H+
(hydrogen ion)
+
e(electron)
Oxygen is used to create ATP as hydrogen atoms and electrons meet with water
The electron transport chain consists of a chain of hydrogen ion-electron pairs,
linked to the cell mitochondria. Energy is released in a controlled step by step
manner as the hydrogen ion-electron pairs are passed downwards from a higher
level of energy to a lower-level of energy (each reaction is exothermic). For each pair
of hydrogen ion-electrons that enter this pathway, there is production of three
molecules of ATP and one molecule of water.
The total possible yield produced by the aerobic metabolism is 36 or 38 molecules of
ATP – the total energy yield is dependent on the biochemical pathway taken by the
food fuel. This is the maximum possible ATP yield from the oxidation of one
molecule of glucose.
It takes approximately 3 minutes to extract 95% of the energy available from a
glucose molecule
The overall equation that expresses aerobic respiration is:
Glucose + Oxygen = Carbon Dioxide + Water + Energy
C6H12O6 + 6O2 = 6CO2 = 6H20 + Energy
Think long distance running
This supplies the body with a prolonged and steady supply of energy.