ENERGY SYSTEMS
LESSON 4
Aerobic Energy System
LEARNING OBJECTIVES
1.
Am I able to explain the Aerobic System?
2.
Can I evaluate the Aerobic System?
STARTER
 Explain
the facts about the Lactic
Acid System
FACTS OF THE LACTIC ACID
SYSTEM

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There is NO Oxygen present!! Therefore, the Lactic Acid
System works under Anaerobic conditions
The fuel for this system is Carbohydrates (in the form of
Glycogen)
The reactions take place in the sarcoplasm of the muscle
cells
The main limitation of this system is the Onset of Blood
Lactate Accumulation (OBLA) – which lowers the pH
and inhibits enzymes
The Lactic Acid system is the predominant energy system
for the 400m sprint and for midfield games players that
have lots of high intensity sprints with no time for recovery
AEROBIC ENERGY SYSTEM
Look at sheet provided about the Aerobic
System
 Explain what is happening during:

Aerobic Glycolysis
 Krebs Cycle
 Electron Transport Chain

AEROBIC GLYCOLYSIS
 This
is the same reactions as Lactic
Acid System, apart from Pyruvic
Acid combines with coenzyme A
to form Acetyl CoA due to oxygen
being present
KREBS CYCLE


The Acetyl CoA combines with oxaloacetic acid
to form Citric Acid
Citric acid is then taken into the Krebs Cycle
where:
CO2 is produced and removed via the lungs
 Hydrogen atoms are removed (oxidation)
 Energy is produced to re-synthesis 2 molecules of
ATP
 Oxaloacetic acid is regenerated

ELECTRON TRANSPORT CHAIN

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The Hydrogen atoms (from Krebs Cycle) Combine
with the coenzymes NAD and FAD to form NADH
and FADH
These are then carried down the Electron Transport
Chain where hydrogen is split into H+ and e
This takes place in the cristae of the mitochondria
where three important events take place:


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The hydrogen electron (e‾) splits from the hydrogen atom
and passes down the ETC
This provides sufficient energy to re-synthesise 34 ATP
molecules
The hydrogen ion (H+) combines with oxygen to form water
(H2O)
TASK


Explain how ATP is re-synthesised in the
Aerobic System
You must include information on the following:
Aerobic Glycolysis
 Krebs Cycle
 Electron Transport Chain

FATS

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Triglycerides (fats) are broken down by enzymes termed
lipases into free fatty acids (FFA) and glycerol and used
as an energy fuel within the aerobic system
FFA are broken down into Acetyl CoA, which enters and is
broken down by the Krebs Cycle and the ETC in the
process termed beta-oxidation
FFA produce more Acetyl CoA and consequently produce
far greater energy than the breakdown of glycogen/glucose
However, FFA’s require 15% more O2 than that required
to break down glucose
Therefore, glycogen and glucose are the preferred energy
fuel during moderate or high intensity activity
TRAINING ADAPTATIONS

Aerobic training causes a number of beneficial adaptations
which help to improve the aerobic energy system’s efficiency to
re-synthesise ATP:
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Increased storage of muscle and liver glycogen
Increased metabolism of aerobic enzymes
Earlier use of FFA’s as a fuel thereby helping to conserve
glycogen stores
The net effect of the above adaptations is that they
increase/prolong the aerobic threshold thereby increasing the
potential intensity of performance
This delays muscle fatigue by increasing the intensity at which
the onset of blood lactate accumulation is reached and by
maximising its efficiency to remove lactate during periods of
recovery
ADVANTAGES OF THE
AEROBIC ENERGY SYSTEM

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Large potential glycogen and Free Fatty Acids (FFA)
stores available as an efficient energy fuel
Efficient ATP re-synthesis when good O2 supply
guarantees breakdown of FFA
Large ATP re-synthesis. 38 ATP from one molecule of
glucose, compared to 2 from LA system and 1 from
ATP/PC system
Provides energy for low/moderate intensity, high
duration exercise (3 minutes to 1 hour)
No fatiguing by-products. CO2 and H2O are easily
removed
DISADVANTAGES OF THE
AEROBIC ENERGY SYSTEM
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Slower rate of ATP re-synthesis compared with
LA system
Requires more O2 supply (15% more for FFA)
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
FACTS OF THE AEROBIC
SYSTEM
The Aerobic System works under Aerobic
conditions
 The fuel for this system is Glycogen or
Fat as well as requiring Oxygen to
function
 The reactions take place in the sarcoplasm
of the muscle cells, Matrix of the
Mitochondria and Cristae of the
Mitochondria

PLENARY
 Explain
how the three energy systems
would work throughout a Football
match