Aerobic system

1. Production of ATP
using the Aerobic
System

2. Aerobic system of energy production needs oxygen
At onset of activity, although oxygen is present in
the muscles there isn’t enough to break down
fuels into energy.
So for immediate energy production the
anaerobic systems are used ieATP-PC system
Lactic Acid System
As soon as we start to exercise heart rate and
breathing rate increases so more oxygen is getting
to the muscles.
Within a few minutes the muscles are supplied with
enough oxygen for aerobic respiration to work.

3. Aerobic energy is used for low to moderate
intensity and long duration.
It offers a high energy yield, allowing
activity to be maintained for long periods.

5. Elite athletes may use
their aerobic pathways
to perform what would
be high intensity to
lesser athletes.

6. Aerobic System uses
oxygen to break down
food fuels.
This gives off a high energy yield.
Carbohydrates and fats

7. Three stages of the
aerobic pathway
Stage 1 : Glycolysis
Stage 2 : Kreb’s Cycle
Stage 3 : Electron Transport Chain

8. Stage 1
glycolysis
Glycogen
Pyruvic Acid (pyruvate)
Glycolysis
ENE
RGY
ADENOSINE P P
ADENOSINE P P
P
P

9. As oxygen is present the pyruvic acid is NOT
converted into lactate.
Instead it is converted into
acetyl-coenzyme-A (CoA)
Acetyl Co-A moves to the mitochondria within the
muscle cell where energy release now takes place.

10. Stage 2 Kreb’s
Cycle
Takes place inside the matrix of mitochondria.
As Acetyl CoA enters the matrix it triggers a
complex cycle of reactions called Kreb’s Cycle.
From these reactions
energy is produced to resynthesise 2 molecules
of ATP.
carbon dioxide is formed.
hydrogen is taken to the electron transport
chain.

11. Stage 3 electron
transport chain
Hydrogen is carried to the electron transport
chain.
This occurs in the cristae of the mitochondria.
Hydrogen splits into hydrogen ions and
electrons.
Hydrogen ions are oxidised to form water.
Hydrogen electrons provide energy for
resynthesis of ATP (34 molecules)

12. Total energy yield from
the aerobic system is
38 molecules of
ATP

13. The aerobic system is the most efficient in
energy production.
The by-products (water and carbon dioxide) are
easily expelled.
The system relies on the availability of oxygen.
However…

14. Sub-maximal
exercise will
predominantly use
this system as
oxygen can be
delivered at a rate
to match the
demand for oxygen

15. Unless the body runs out of
carbohydrate and fat
stores, this system is
unlimited.

16. summary
Stage 1
Glycolysis
(Sarcoplasm)
Stage 2
Kreb’s Cycle
(Mitochondria)
Stage 3
Electron Transport
Chain
(Mitochondria)
Glycogen
Pyruvic
Acid
Acetyl
Coenzyme A
ENER
GY
ADENOSINE P P
ADENOSINE P P
P
P
Acetyl
Coenzyme A
ADENOSINE P P
ADENOSINE P P
P
P
ENER
GY
Carbon Dioxide Hydrogen
Hydrogen
Water
ADENOSINE P P P
34
ENER
GY

17. Glycogen
Pyruvic Acid
Acetyl
Coenzyme A
Carbon
Dioxide
Electron
Transport
Chain
2ATP
2ATP Glycolysis
34ATP
Water
Krebs
Cycle
Oxygen
present
Hydrogen

18. Fats can also be broken
down to produce energy
to resynthesise ATP

19. Triglycerides
(stored fat in muscle)
Glycerol and
Fatty Acids
Beta Oxidation
Lipase
Carbon
Dioxide
Electron
Transport
Chain
Energy
130 ATP
Water
Kreb’s
Cycle
Acetyl
Coenzyme A
Hydrogen

20. Lots more ATP can be resynthesised (38 moles
of ATP from 1 mole of glycogen).
The body has large stores of muscle glycogen
and triglycerides so exercise can last for
several hours.
Oxidation of glycogen and fatty acids do not
produce any fatiguing by products.
Advantages of the
aerobic system

21. Takes a while for sufficient oxygen to be
available to breakdown glycogen and
triglycerides.
Therefore this system cannot provide energy for
ATP resynthesis straight away or during high
intensity activity.
disAdvantages of the
aerobic system

22. How can this system be improved?
Increased muscle stores of glycogen &
triglycerides.
Increased number of oxidative enzymes.
Continuous training
Fartlek training

23. The triathlon is an athletic event that involves performers
undertaking a long distance swim, immediately followed by a
cycle race and then finally a run of several kilometres.
What would be the major energy sources used by a
triathlete? (3 marks)
Briefly explain how these energy sources are used for
regeneration of ATP. (5 marks)

24. Fats
Fatty acids
Glycerol
Triglycerides (sub max 2 marks)
Carbohydrates
Glycogen
Glucose (sub max 2 marks)
What would be the major energy sources used by a
triathlete? (3 marks)

25. Briefly explain how these energy sources are used for
regeneration of ATP. (5 marks)
Carbohydrates/glycogen broken down into glucose then
into pyruvate.
Called glycolysis.
Some ATP is produced.
In presence of oxygen, pyruvic acid converted into
acetyl coenzyme A.
Enters mitochondria where Kreb’s cycle takes place.
Carbon dioxide and energy produced to resynthesise 2
molecules of ATP.
Hydrogen is carried to electron transport chain.
Water produced and energy to resynthesise 34ATP.

26. Considers the importance of each
energy system in a particular
activity.
Intensity and duration will decide
which energy system is used.
Often there will be a combination of
all three.
Energy continuum

27. Energy continuum
Example: Marathon Runner
ATP-PC System – Start
of race.
Aerobic System –
Majority of race.
Lactate Anaerobic
System – Sprint
finish.

28. Example: Midfield in football
ATP-PC System – Sprinting
for the ball.
Lactate Anaerobic System –
High intensity work, chasing
ball, moving into space,
dribbling with ball.
Aerobic System – Less
intense periods when play
does not involve the player.
Time to recover using
aerobic system.

29. Energy continuum

30. Energy supplied against time
A = ATP-PC - Lactic Acid threshold. The
point at which ATP-PC system is exhausted
and the lactic acid system takes over.
B = Lactic Acid - Aerobic threshold.
The point at which the lactic acid
system is exhausted and the aerobic
system takes over.
ATP-PC
Lactic Acid
Aerobic

32. Phosphocreatine broken down by creatine kinase.
Energy released is used to resynthesise ATP.
Aerobic system used for recovery.

33. THE EFFECTS OF RELIEF PERIODS FOLLOWING INTERMITTENT EXERCISE ON
THE LEVELS OF ATP-PC STORES IN MUSCLE.
ATP-PC
STORES
TIME
WORK RELIEF WORK RELIEF WORK
i) ATP-PC stores are exhausted rapidly in high
intensity/short duration activities. 8-9 secs in average
individual
ii) Possible to achieve regeneration by up to 50% after 30
seconds rest
iii) Can regenerate in game by walking or standing but
supplies only go back up to approx 90% then down then
back up to approx 80% then down etc.

34. At low intensity, the aerobic system is used.
Fats, glycogen and carbohydrates broken down.
Acetyl Coenzyme-A enters Kreb’s cycle in mitochondria.
Carbon dioxide produced and a small amount of energy
to resynthesise ATP.
Hydrogen taken to electron transport chain.
Lots of energy given off.
As intensity increases, there will be a lack of oxygen.
So ATP produced through lactic acid system.
Glycogen broken down into pyruvic acid giving off energy
to resynthesise ATP.
As no oxygen present pyruvic acid converted to lactate.

35. In part (d)(ii), a disappointingly large
proportion of candidates suggested that the
energy systems somehow work in a sequence
suggested by interpreting the x-axis of
Figure 3 as simply duration of a single event,
rather than as duration of differing events.
Better answers, though rarer, did manage to
suggest that a long-distance run was
predominantly an aerobic activity, which
became anaerobic as the intensity increased.

36. RATEOFENERGY
PRODUCTION
% OF MAXIMUM RATE OF ENERGY PRODUCTION
TIME
2 SECS 10 SECS 60 SECS 2 HOURS
OVERALL
PERFORMANCE
ATP-PC
SYSTEM
LACTACID
SYSTEM
ATP STORE
AEROBIC SYSTEM