Energy systems
Learning outcomes:
All are able to demonstrate understanding of the
energy sources required for ATP resynthesis
All are able to describe the Lactic Acid energy
system
Most are able to explain the use of PCr in ATP
resynthesis
Most are able to apply their understanding of the
lactic acid system to sporting examples.
 Some can analyse the lactic acid and determine
advantages and disadvantages
Starter activity
Research has been conducted into “activity cycles” of intermittent
sports such as soccer, hockey and rugby, which are reliant on
efficient energy systems.
a) Identify the principal energy source for each of the
following activity cycles in these types of physical
activities:
(i) walking;
(ii) sprinting;
(iii) jogging. (3 marks)
b) What are the disadvantages of using fat as an energy source
during exercise? (2 marks)
Answer
a) i)Walking – free fatty acid /triglycerides/fats;
ii) Sprinting-muscle glycogen/ATP/carbohydrates/PC;
ii) Jogging-mixture of fatty acids and muscle
glycogen/fats/carbohydrates
3 marks
b) 1 Less efficient energy yield per unit of oxygen;
2 Cannot be used anaerobically for sprint type activities/
can only be used aerobically;
3 Requires the presence of carbohydrates to be used;
4 Slow to produce energy/ insoluble in blood. 2 marks
Homework
 List ten different activities where a performer might benefit from taking a
creatine supplement. Give reasons in support of your answer
 Research and make notes on the factors that affect the rate of lactate
accumulation:
Muscle fibre type
 Exercise intensity
 Rate of blood lactate removal
 Training
 Respiratory exchange ratio
 OBLA can be expressed as a percentage of VO2 max. What do you understand
by this term and how is it different in trained and untrained performers. What
factors affect VO2 max?

Energy systems
 The conversion of these fuels into energy which can
then be used to resynthesise ATP occurs through one
of 3 energy systems:
 1-The ATP-PC System
 2- The Lactic Acid System
 3- The Aerobic system
The Energy Systems
Immediate:
ATP-PCr
Short-term:
Lactic acid
(glycolysis)
Long-term:
Aerobic
Energy Systems: What we need
to know
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The type of reaction (eg. Aerobic or anaerobic)
The chemical or food used (eg. Glycogen)
The specific site of the reaction
The energy yield (eg. 2ATP from lactic acid system)
Specific stages within a system
The by-products produced (eg. Lactic acid)
The enzyme controlling the reaction.
When each system is predominantly used during exercise
ATP –PC System
 ATP-PC system is the first of the anaerobic systems.
 Energy is released rapidly so used for high intensity
maximum work
 There is a limited store of phosphocreatine in the
muscles and can only last for 3 - 10 seconds
 100m sprint, performing a vault, smash in tennis, slam
dunk
ATP-PC System
 Phosphocreatine (PCr) stored in the sarcoplasm of the
muscles
 The following reaction takes place (facilitated by the
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enzyme creatine kinase)
PCr ------------ Pi + Creatine + Energy
This energy is used to recycle ATP
Energy + ADP + Pi = ATP
These two reactions together are called a coupled reaction
 Only 1 molecule of ATP can be resythesised by 1 molecule
of PC
Activity
 Critically analyse the ATP – PC system.
 What are the strengths and weaknesses of this system
to an athlete.
ATP-PC System
Advantages
Disadvantages
 ATP resynthesis is very rapid
 Limited store of PCr in
 PCr stores recover very
quickly (2-3 mins)
 Anaerobic process
 No fatiguing by-products
 Can use creatine
supplementation
muscle cell, sufficient for 10
secs
 Fatigue occurs when PCr
levels fall and can not sustain
ATP resynthesis
 Resynthesis of PCr needs
sufficient oxygen
 Only 1 molecule of ATP can
be resythesised by 1 molecule
of PC
Quick recap
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Site of reaction –
Fuel used –
Active enzyme –
Molecules of ATP
produced -
100m sprintATP split to drive away from blocks
PCr supplies energy for rest of race
ATP SPLITTING
 muscle cell
 ATP
 ATPase
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ATP-PC SYSTEM
muscle cell
Phosphocreatine
Creatine kinase
1 molecule
ATP-PC System
Tip: Rebuilding or resynthesising ATP from ADP + P
is an endothermic reaction
(energy is required)
Activity
 Using the pictures demonstrate your understanding of
the Lactic Acid system (Anaerobic glycolysis).
 One person in your group will move to another group
to share your understanding and gain further
knowledge.
 Summarise your understanding of the Lactic Acid
system.
 Extension - analyse the system and determine its
advantages and disadvantages
Lactic Acid System
 Most activities last for longer than 10 secs.
 Once phosphocreatine is depleted the lactic acid
system (anaerobic glycolysis) takes over and re
synthesises ATP from the breakdown of glucose.
 Glucose is stored in the muscles and liver as glycogen.
 In order to provide energy to make ATP glycogen has
to be converted to glucose. This process is called
glycolysis. (Sarcoplasm)
Lactic Acid System
 Glucose is broken down
into 6 phosphates (2
ATP) and pyruvic acid.
 The main enzyme
responsible for the
break down of glucose
is phosphofructokinase
(PFK) activated by low
levels of
phosphocreatine
 Pyruvic acid is
converted into lactic
acid in the absence of
oxygen.
Lactic Acid system
 Overall summary:
 C6H12O6 (glucose)  2(C3H6O3) (pyruvic acid) + ENERGY
 ENERGY  2ADP + 2Pi  2ATP
 The energy released from the breakdown of each molecule
of glucose is used to make two molecules of ATP
 The lactic acid system actually provides sufficient energy to
re-synthesise three molecules of ATP but the process of
glycolysis itself requires energy (one molecule)
 The lactic acid system provides energy for high-intensity
activities lasting up to 3 minutes but peaking at 1 minute,
for example the 400m
Lactic Acid System
Advantages
Disadvantages
 Few chemical reactions so
 If lactic acid accumulates in the
ATP can be resynthesises
quickly
 Anaerobic so do not need to
wait for the 3 minutes or for
sufficient oxygen
 Lactic acid can be converted
back into liver glycogen
 can be called upon to produce
an extra burst of energy
(10,000m)
muscle, the pH of the body is
lowered and this has an effect on
enzyme action. PFK, the
controlling enzyme, is then
inhibited and the ability to regenerate ATP is reduced. This
affects performance, for example
‘burning out’ at the end of a race
 Only a small amount of energy
(5%) locked inside a glycogen
molecule can be released in
absence of oxygen.
Quick recap
400m race
First 10 secs ATP-PC
Lactic Acid will provide for the rest
 Site of reaction –
 Fuel used –
 Active enzyme –
 Molecules of ATP
produced -
 Sacroplasm of muscle
cell
 Glycogen (stored CHO)
 Phosphofructokinase
 2 molecules
Exam Question
 What are the main energy sources used by an athlete
during a 400M sprint? Explain the predominant
energy system used during this time.
(7 Marks)
Make notes on your own to answer this question.
Share with the person beside you.
Share with the whole class.
Candidate A
 The main energy sources used by a 400m runner are
carbohydrate and phosphocreatine. The ATP/PC
system is used for the first part of the race and is a
simple system to use. It uses phosphocreatine as the
fuel and there are no fatiguing by products. The energy
yeild is ATP. After 10 seconds the lactic acid system is
used.
Candidate B
 The energy sources used by the sprinter are
phosphocreatine and glucose. The main energy
system is the lactic acid system. This is anaerobic and
glucose is broken down into pyruvic acid. Two
molecules of ATP are formed and lactic acid is the by
product. This system takes place in the sarcoplasm.
Energy systems
Learning outcomes:
All are able to demonstrate understanding of the
energy sources required for ATP resynthesis
All are able to describe the Lactic Acid energy
system
Most are able to explain the use of PCr in ATP
resynthesis
Most are able to apply their understanding of the
lactic acid system to sporting examples.
 Some can analyse the lactic acid and determine
advantages and disadvantages
Plenary Activity
 All write down one question and answer that would
demonstrate the progress you have made in this
lesson.