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Energy Systems:

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Horace Reid Dennis

on 9 October 2015

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Transcript of Energy Systems:

Energy Systems:
Key Terms:
Energy:
The capacity of the body to perform work......

Adenosine Triphosphate:
The energy currency of the cells. ATP is the only direct source of energy for all energy requiring processes in the body.
Sources of energy in the body.....
Chemical energy in the body is stored in an easy access, energy rich compound called
A
densosine
T
riphos
p
hate (ATP). ATP exists in all cells and consist of a number of atoms held together by energy bonds. It is through breaking down these bonds that energy is released for those processes in the body that require energy.

ATP
When energy is required, the enzyme ATPase is released which initiates the brekadown of ATP. It is the outermost bond of ATP that most interests ATPase as it is this bond that stores most energy.
Through the breakdown of ATP energy is released leaving Adenosine Diphosphate (ADP) and an inorganic phosphate (Pi).
Recycling ATP
There is only a limited supply of ATP within the muscle cell, probably only enough to perform for example, a maximal weight lift in the gym or a sprint start for 2 or 3 seconds.

There ATP is constantly recycled to ensure a continuous supply of energy. However recycling energy OR resynthesising of ATP itself requires energy and this energy is acquired from the food that we eat!!!
Key Terms:
Exothemic reaction:
A chemical reaction that releases energy.
Phosphocreatine:
A high energy compound which exists in the muscle cells alongside ATP and provides the energy for ATP resynthesis when the intensity of exercise is very high
Anaerobic metabolism:
The release of energy through the breakdown of food fuels in the absence of oxygen
Aerobic metabolism:
The release of energy through the breakdown of food fuels in the presence of oxygen.

The fuels for ATP re-synthesis are derived from the following sources.....
Phosphocreatine
: Phosphocreatine (PCr) is used to resynthesise ATP in the first 10 seconds of intense exercise. To help facilitate this immediate
re- synthesis of ATP, PCr is stored within the muscle cell itself alongside ATP. However stores of PCr are limited
Good dietary sources of creatine include red meat and fish

The fuels for ATP re-synthesis are derived from the following sources.....
Glycogen (stored carbohydrate): Glycogen is stored in the muscles
(350g)
and liver
(100g)
. It is first converted to glucose before being broken down to release the energy for ATP re-synthesis. During high intensity exercise glycogen can be used without the presence of oxygen
(Anaerobic Metabolism)
. However much more energy can be released from glycogen during aerobic metabolism when oxygen is available. Stores of glycogen are maintained through eating complex carbohydrates such as pasta and porridge oats.
The fuels for ATP re-synthesis are derived from the following sources.....
Triglycerides (muscular stores of fat): At rest up to two thirds of our energy requirements is met through the breakdown of fatty acids.

This is because fat can provide more energy per gram than glycogen

(1g of fat provides 9.1kcal of energy compared to 4.1 kcal of energy for every 1g of glycogen.

The fuels for ATP re-synthesis are derived from the following sources.....
Proteins: Protein is the least favoured sources of energy only contributing 5-10% of the total energy yield. In the presence of oxygen protein is used as an energy provider, usually when stores of glycogen are low.
Good dietary sources of protein include meat, fish and dairy products.
Remember...protein's primary function is to facilitate the growth and repair of the body's cells including muscle tissue

The Aerobic (oxidative energy system).....
During resting conditions or during exercise where the demand for energy is low, oxygen readily available to release stored energy from muscle glycogen, fats and proteins. The aerobic system is the body's preferred energy pathway as it is by far the most efficient in terms of ATP resynthesis.

The energy yield from aerobic metabolism is
18 times greater
than that gained from anaerobic processes

Sources of energy in the body.....
Under anaerobic conditions
pyruvic acid (pyruvate)
is converted into fatigue-inducing lactic acid by the enzyme lactate
dehydrogenase (LDH)
. However when oxygen rich supply, pyruvic acid instead converted into
acetyl-coenzyme-A
by combining with the enzyme pyruvate dehdrogenase.

The site for energy release now moves to specilised parts of the cell know as;
mitochondria
.

Fats can only be used as an energy sources when there is a plentiful supply of oxygen and must be used in conjunction with glycogen. This is because the transport of fatty acids in the blood is poor & slow due to their low solubility (dissolve)
Consequently fatty acids do not arrive at the muscle cell in sufficient quantities to sustain muscle contraction on their own. Glycogen must therefore provide the supplementary energy
The Kreb Cycle.....
The Krebs cycle takes place in the fluid-filled matrix of the mitochondria which has a rich supply of enzymes that are ready to perform the necessary chemical reactions to help the remaining energy stored within the molecule.

Energy systems.....
The conversion of these fuels into energy which can then be used to resynthesise ATP occurs through one of three pathways of energy systems.
It is the
intensity
and
duration of the exercise
that dictates whether
oxygen is present
and ultimately which energy system predominates.
(1) The aerobic (oxidative system)
(2) The lactic acid or lactate anaerobic system
(3) The ATP-PC or alactic system

Key Terms.....
Mitochondrion:
The powerhouse of the cell. Mitochondria are specialised structures within all cells that are the site of ATP production under aerobic conditions.
Krebs cycle:
A series of chemical reactions that occur in the matrix of the mitochondria yielding sufficient energy to resynthesis 2 ATP molecules and carbon dioxide....forming part of the aerobic system.
Electron transport system:
A series of chemical reaction in the cristae of the mitochondria where the majority of energy is yielded for ATP resynthesis. 34 moles of ATP can be resynthesised from just 1 mole of glycogen at this stage of the aerobic system.

(1) The oxidation of citric acid.....
This involves the removal of hydrogen atoms from the compound which enter the final stages of the aerobic system
(2) Production of carbon dioxide.....
The removal of hydrogen means that only carbon and oxygen remain. These combine to form carbon dioxide which is carried to the lungs where it is breathed out.
(3) Resynthesis of ATP.....
Sufficient energy is released at this stage re resynthesise 2 moles of ATP
The electron transport system.....
The final stage of glycogen breakdown occurs in the
cristae
of the mitochondria. Hydrogen given off at the krebs cycle stage is carried to the electron transport system.

(1) Water (H20).....
Is formed when the hydrogen ions (H+) AND electrons (e-) combine with oxygen through a series of enzyme reactions
(2) Resynthesis of ATP.....
By far the majority of energy is released here for the resynethesis of ATP. 34 moles of ATP can be resynthesised, making this by far the most efficient sources of energy in the body.
Other fuels used in aerobic energy production.....
Fat and protein can also be metabolised under aerobic conditions to form C02H20 and energy for ATP resynthesis. Fats stored in the muscle as triglycerides must first be broken down into glycerol and free fatty acids (FFAs) before they go through the process of beta-oxidation.

Following this fatty acids can enter the krebs cycle where they can then follow the same path of metabolism as glycogen.

Consequently fatty acids become the preferred fuel as the duration of the activity/ exercise increases...... for endurance performers as it enables them to spare their glycogen for later in the event of competition
Advantages to the athlete of using the aerobic system.....
(1) Significantly more ATP can be resynthesised under aerobic conditions than anaerobic... 36ATP / 2ATP (1 mole of glycogen)
(2) The body has substantial stores of muscle glycogen and triglycerides enable exercise to last for several hours
(3) Oxidation of glycogen and fatty acids do not produce any fatiguing by products

Drawbacks to the athlete of using the aerobic system.....
(1) When we go from resting state to exercise it takes a while for sufficient oxygen to become available to meet the new demands of the activity and enable the complete breakdown of glycogen and fatty acids.
(2) Can not provide energy to resynthesise ATP in the immediate short term.
(3)The transport of fatty acids to the muscle is slow and requires 15% more oxygen than that required to break down the equivalent amount of glycogen.
(4) Due to the low solubility of fatty acids the endurance athlete will usually use a mixture of both glycogen & fatty acids to provide energy for ATP resynthesis. When glycogen become depleted and the body attempts to metabolise fatty acids as a sole source of fuel, muscle spasms may result...know as "hitting the wall".
The aerobic system and recovery.....
The recovery process is concerned with returning the body to its pre-exercise state so that heart rate, oxygen consumption, blood lactate levels and glycogen stores are exactly the same levels as they were before the exercise commenced.

Excess post exercise oxygen consumption.....
EPOC represents the extra volume of oxygen consumed following exercise that enables the body to fully recover and return to its pre-exercise state.

Researchers with in this field have identified two stages of recovery:
(Stage 1) - Fast replenishment stage
(Stage 2) - Slow replenishment stage


Fast replenishment stage.....
The first component of EPOC. Oxygen consumed is used to re-saturate myoglobin and resynthesise ATP and PC. It takes approximately 2-3 minutes.


V02 Max.....
VO2 Max - The maximum volume of oxygen that can be utilised or consumed by the working muscles per minutes.....
it is usually measured in ml/kg/min
Factors affecting Vo2 max
Physiology
Lifestyle
Genetics
Gender
Age
Body composition
Training
Slow replenishment stage.....
The second component of EPOC. oxygen consumed during this stage is largely used to remove lactic acid which takes about 1 hour. in addition oxygen is also used to maintain cardiac and respiratory rates and normalise body temperature.
The anaerobic energy system.....
Muscular stores of ATP will have depleted after about 3 seconds of maximal activity !!!!!
For high intensity activity to continue the immediate recycling of ATP is necessary
HOWEVER
..... The rapid increase in activity results in insufficient oxygen being available (an oxygen deficit) to sustain the the ATP resysnthesis.
PCr -------------Creatine + pi + energy

The body therefore relies upon a second energy rich compound found alongside ATP in the muscle cells......phospocreatine. This compound is broken down in the sarcoplasm and is facilitated by the enzyme creatine kinase.
The anaerobic energy system.....
The energy released from the breakdown of phophocreatine is not used for muscle contraction but is instead used to recycle ATP, so that is can once again be broken down to maintain a constant energy supply.

As energy is required for this reaction to take place it is know as the
endothermic
reaction
Advantages to the athlete of using The anaerobic energy system.....
(1) ATP can be resynthesised very easily
(2) PCr stores are recovered very quickly with 2-3 minutes of exercise stopping........meaning high intensity activity can once again be undertaken
(3) It is anaerobic process and so does not need to wait for sufficient levels of oxygen to be present
(4) There are no fatiguing by products which could delay recovery
(5) Most athletes nowadays use creatine supplementation
Drawbacks to the athlete of using The anaerobic energy system.....
(1) Only limited supply of PCr stored in the muscle cell....sufficient resynthesise ATP for approximately 10 seconds or so. Fatigue occurs when concentrations of PCr fall significantly and no longer sustain ATP resynthesis
(2) Resynthesis of PCr can only take place when there is sufficient ___________ available
(3) Only 1 mole of ATP can be recycled through 1 mole of PCr
Coupled reaction.....
A reaction where the product of one reaction is used to facilitate the 2nd reaction

EG The ATP-PC system
The lactic acid (lactate anaerobic) system).....
As we all know most activities last longer than the 10 second threshold of the ATP-PC system!!!

If strenuous exercise is required to continue, ATP must be resynthesised from another fuel source.......
Therefore the body switches to Glycogen to fuel the working muscles once phosphocreatine stores have been depleted

The lactic acid (lactate anaerobic) system).....
The glycogen stored in the liver and muscles must first be converted into glucose 6phosphate before it is broken down to
pyruvate
by the enzyme
phosphofructokinase
in a process know as
glycolsis.

During glycolsis which takes place in the ___________ that energy is released to facilitate the ATP resynthesis. For every mole of glycogen broken down 2 moles of ATP are gained!!!!
In the absence of oxygen pyruvate is converted into lactate (lactic acid) by the enzyme lactate dehdrogenase (LDH)
Advantages of this system.....
(1) Few chemical reactions.....ATP can be resynthesised relatively quickly for activity bouts of exercise that last between 10 seconds and 3 minutes
(2) It is an anaerobic process and so does not need to wait for the three minutes for sufficient oxygen to be present
(3) Any lactic acid that has accumulated can be converted back into liver glycogen or indeed by used as a metobloic fuel by reconversion into pyruvate and entry into the aerobic system

Drawbacks of this system.....
(1) The most obvious drawback of this system is the accumulation of lactic acid which can make glycolytic enzymes acidic. This causes them to lose their catalytic ability, inhibiting energy production through glycolysis. The intensity of the exercise must be reduced or even in some cases stopped so that the body can remove the lactic acid that has been accumulated.
(2) Only a small percentage of energy (5%) within out glycogen molecule can be released in the absence of oxygen. The remaining 95% can only be released in the presence of oxygen.

Lactate sampling and measuring OBLA.....
(1) OBLA can only truly be measured in a sports science laboratory

Tests procedure ....... bouts of 5 mins exercise...... gradual increase in intensity...heart rate, oxygen consumption and blood lactate recorded...... to monitor progress and assess exercise intensity during training

Onset of blood lactate accumulation.....
A large v02 max sets the ceiling for endurance performance and is an indication of the size of our aerobic performance engine. However it is the onset of blood lactate accumulation (OBLA) that determines the actual percentage of the engine power that can be utilised.
OBLA describes the point at which lactic acid starts to accumulate in the muscles.
55-60% = average untrained individual
85-90% = trained endurance performer

OBLA & Training.....
Improvements in endurance capacity can be observed where lower lactate levels are recorded for any given exercise intensity.
This shows that the body has adapted to cope with higher levels of blood lactate and increased the rate of its removal through effective
buffering
.

What is buffering......?
A process which helps in the removal of lactic acid and maintains blood and muscle PH acidity.

The respiratory exchange ratio (RER).....
The respiratory exchange ratio is the ratio of the volume of carbon dioxide expired per minute to the volume of oxygen consumed per minute and is used used by the coach and athlete as measure of the intensity at which the athlete is training.

Exam Questions.....
Explain how energy is provided, allowing the athlete to complete the shot put.
(3 marks - June 2013)
A. Stored ATP
B. Alactic system/ATP-PC system/Phosphocreatine system/ATP-CP system
C. PC breakdown
D. To creatine and phosphate/C and P
E. Energy used/released to perform the contraction/re-synthesis for ATP

Exam Questions.....
Identify the energy sources that a performer may use during competition.
(3 marks - June 2013)
A. Carbohydrates/Glucose/Glycogen
B. Protein/Lactate/Amino acids
C. Fats/Fatty acids/Glycerol/Triglycerides
D. Creatine/phosphocreatine

Exam Questions.....
Explain the terms lactate sampling and respiratory exchange ratio. (4 marks - June 2012)
A. (Lactate sampling) – taking blood samples (to measure the level of lactic acid)
B. Ensures training is at the correct intensity/monitor improvements over time
C. Provides accurate/objective measure
D. Measures OBLA/lactate threshold/occurs at 4 mmols
Sub max of 2 marks
E. (Respiratory Exchange Ratio) – ratio of carbon dioxide released compared to oxygen used by the body
F. Estimates use of fats and carbohydrates used during exercise/ calculates energy expenditure
G. Tells if performer working aerobically/anaerobically/energy system used
H. RER close to 1 performer using carbohydrates/close to 0.7 using fats/respiratory quotient
Exam Questions.....
Using your knowledge of energy systems, outline and explain the relationship between energy
sources and intensity of exercise. (7 marks - June 2012)
A. At low level of exercise energy comes from a mixture of fats and carbohydrates;
B. Broken down aerobically/using oxygen/aerobic system;
C. Glycolysis/Anaerobic Glycolysis – glucose broken down/pyruvic acid/pyruvate formed
D. Beta oxidation breaks down fats/tri-glycerides/free fatty acids
E. Krebs Cycle – oxidation of acetyl-coenzyme-A/Citric acid production
F. Electron transport/transfer chain – water formed/hydrogen ions/protons used
G. At high levels of intensity carbohydrates are only energy source/as intensity increases, more carbohydrates used;
H. At high intensity fat use limited by oxygen availability/no fats used anaerobically/lack of oxygen;
I. Slower energy release from fats/quick release of energy from carbohydrates;
J. (Carbohydrate break down) Lactic Acid System/Lactate anaerobic system
K. No oxygen used/anaerobic
L. Glycolysis/Anaerobic Glycolysis – glucose broken down/
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