Transcript ATP ENERGY PRODUCTION

ATP: ENERGY PRODUCTION
ATP
Energy
• The body needs a constant supply of energy to
perform every day tasks such as respiration
and digestion.
• Energy is the capacity to perform work and is
measured in joules or calories.
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Calorie, Joule and Watt
• Calorie is the amount of heat energy needed
to raise the temperature of 1 gram of water
through 1oC.
• A Kilocalorie (kCal)is 1000 calories.
• Joule = 4.2 kCal.
• A Watt is equivalent to the use of one joule
per second.
• Power is the work performed per unit of time
and is measured in watts.
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Work
• Work is defined as force x distance.
• It can be measured in calories and joules.
Food
• Food is chemical energy.
• It is converted into movement (kinetic
energy).
• Or is stored as potential energy.
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Energy release in the body
• There is only 1 usable form of energy in the body
– adenosine triphosphate (ATP).
• All food we eat has to be converted into ATP.
• ATP is the body’s energy currency
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• ATP is a high energy phosphate compound
made up of adenosine and 3 phosphates.
• The bonds that hold the compound together
are a source of a lot of potential energy.
• ATP = adenosine-phosphate-phosphate-phosphate
Structure of ATP
adenosine
Pi
Pi
Pi
Formation of ATP
ATP is made when another molecule called
adenosine diphosphate (ADP) is bonded to a
third inorganic phosphate (Pi) using the
energy released from glucose.
The role of ATP
• ATP stores the energy in the third bond of the
molecule
• The energy is released when that bond is
broken to release the third inorganic
phosphate (Pi)
adenosine
Pi
Pi
Pi
ATP
Enzymes
adenosine
Pi
ADP
Pi
+
Energy
released
to do work
Pi
• When a compound is broken down = bonds
between the molecules are broken = the energy
is released.
• ATP is broken down to adenosine diphosphate
(ADP) and free a phosphate  releasing the
stored energy.
• ATP → ADP + P + Energy
• The energy released from the breakdown of ATP
to ADP and P is converted to kinetic and heat
energy.
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Methods of ATP production
1. The phosphocreatine system (ATP/PC) or alactic
system.
2. The lactic acid system or anaerobic glycolysis.
3. The aerobic system.
• Each method is good at supplying energy for
particular energy demands and duration.
• Systems 1 & 2 are anaerobic = take place without
oxygen
• System 3 is aerobic: requires oxygen.
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ATP Production by Phosphocreatine or
Alactic System
• Phosphocreatine = high energy phosphate
compound.
• Found in the sarcoplasm of muscle.
• Potential energy is stored in the bonds of the
compound.
Phosphocreatine → P+ Creatine + Energy
creatine kinase
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1. Stores of ATP start to diminish
2. Creatine kinase is activated when the level of
ADP in the muscle cell increases.
3. The energy released by the breakdown of PC
is used to convert ADP to ATP.
*Energy has to be liberated by the breakdown of
PC before ATP can be formed.
**Stores of PC in the muscles are enough to
sustain all out effort for about ten seconds.
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• PCr = the only system capable of producing
ATP quickly.
• As PC is stored in the muscle it is readily
accessible as an energy source = beneficial for
activities that demand large amounts of
energy over a short period of time
• No fatiguing by products are released.
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ATP production by the lactic acid
system or Glycolysis
• Also anaerobic taking place in the sarcoplasm.
• It involves the partial breakdown (lysis) of glucose by
glycolytic enzymes.
• The energy needed comes from the food we eat &
breakdown of glycogen during glycogenolysis.
• Glycolysis produces pyruvic acid which is then
converted to lactic acid in the absence of oxygen.
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glucose
glycolysis takes place as
it does not require
oxygen
pyruvic acid
in absence of oxygen
pyruvic acid is turned
into lactic acid.
lactic acid
2 ADP + 2 Pi
2 ATP
ADENOSINE TRIPHOSPHATE (ATP)
Formed in the breaking down of
This causes FATIGUE in the
muscles.
& H+
If there is insufficient
oxygen LACTIC ACID
accumulates
GLUCOSE
This in turn is broken
down by a chemical
reaction to give
PYRUVIC ACID
Outline of Lactic Acid System (anaerobi
glycolysis)
Production of energy for resynthesis of ATP
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LACTIC ACID SYSTEM/ ANAEROBIC GLYCOLYSIS
Glycogen made from glucose from digested food present in all
cells of the body – muscles, liver
When glycogen breaks down it releases pyruvic acid and
energy.
This energy is used to re-build ATP from ADP and P
This system is anaerobic – no O2
Pyruvic acid is removed when O2 is available
BUT: No O2 = Pyruvic acid is converted into lactic acid
Muscles fail to contract fully - fatigue
•
The lactic acid builds up due to the
shortage of O2 = oxygen debt
needs to be paid back once exercise
has finished.
•
Takes about 20 – 60 mins to remove
accumulated lactic acid after maximal
exercise
•
Lactic acid build-up makes muscles feel
tired & painful exercising
anaerobically can only be done for short
periods of time.
Fatigue
• When glycogen is broken down anaerobically
lactic acid is produced.
• If lactic acid accumulates it lowers the pH (H+).
• pH affects action of enzyme:
phosphofructokinase.
• It also affects lipoprotein kinase (breaks down
fat).
• The body’s ability to synthesise ATP is temporarily
reduced = fatigue.
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Aerobic Respiration
Aerobic respiration = respiration with oxygen.
Aerobic system is fatigue resistant = primary
source of ATP for endurance activities.
Aerobic production of ATP happens in the
mitochondria.
Production of ATP using the Aerobic System
• Needs oxygen.
• At the onset of exercise there isn’t enough O2 to break
down food fuels.
• So the first 2 anaerobic systems are used.
• As heart rate and ventilation increase = more oxygen
needs to be transported to working muscles.
• Within 1-2 minutes the muscles are being supplied
with enough O2 to allow effective aerobic respiration.
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glucose + OXYGEN
energy + carbon dioxide + water
(to make ATP)
Aerobic respiration happens in stages:
Stage 1 – Glycolysis
glyco
glucose
lysis
splitting
In glycolysis, a glucose molecule is broken down into
pyruvic acid.
glucose
energy released to
make small quantity
of ATP
(2 molecules)
series of enzyme
controlled reactions
pyruvic acid
Glycolysis does not require oxygen
Stage 1:Aerobic glycolysis
• Aerobic glcolysis is the same as anaerobic glycolysis.
• Glucose is broken down to pyruvic acid.
• As O2 is now present the reaction can proceed
further than in anaerobic glycolysis.
• Lactic acid is not produced.
• Two molecules of ATP are synthesised at this stage.
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Stage 2 – Breakdown of pyruvic acid
The pyruvic acid made in glycolysis
(stage1) still contains a lot of energy
It can only be broken down to release the
rest of the energy in the presence of
oxygen.
pyruvic acid
series of enzyme
controlled reactions
energy released to
make large
quantity of ATP
(36 molecules)
carbon dioxide + water
Stage 2: The TCA/Citric acid/Krebs’
Cycle
• The pyruvic acid produced in the 1st stage
diffuses into the matrix of the mitochondria.
• A complex cyclical series of reactions now occurs.
• During the cycle three important things happen:
1. Carbon dioxide is formed.
2. Oxidation takes place-hydrogen is removed from
the compound.
3. Sufficient energy is released to synthesis 2
molecules of ATP.
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The Kreb’s Cycle.
• The pyruvic acid is taken by the enzyme acetyl
CoA into the Kreb’s cycle in the mitochondria
Glycogen
2 ATP
Lactic acid
*Sarcoplasm*
Pyruvic acid
Acetyl CoA
*Mitochondria*
2CO2
Removed
via lungs
Kreb’s cycle
2 ATP
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Stage 3:The Electron transport
chain/electron transport system
• Series of molecules built into inner mitochondrial
membrane
• transport proteins & enzymes
• transport of electrons down ETC =pumping of H+ to
create H+ gradient
• yields 34 ATP from 1 glucose
• only in presence of O2 (aerobic respiration)
• The H2 atoms removed in stage 2 are transported by
coenzymes to the inner membrane of the mitochondria.
• Uses coenzymes NAD+ and FAD+ to accept e- from glucose
• Electrons passed from one electron carrier to next in
mitochondrial membrane
• As electrons are passed down by electron carries = combine
with O2 and H2 to form water (H20).
• Energy is released which combines ADP with phosphate to
form ATP.
• The total yield of ATP from aerobic respiration is therefore
38 molecules of ATP.
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• Electrons move in steps from carrier to carrier
downhill to O2
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Creatine phosphate and stored ATP – first few
seconds
Glycolysis – after 8-10 seconds
Aerobic respiration –after 2-4 min of exercise
Repayment of oxygen debt – lactic acid converted
back to pyruvic acid, rephosphorylation of creatine
PC
system
Glycolysis
Aerobic
Respiration
Oxygen
Debt
Comparison of aerobic and anaerobic
respiration
Aerobic respiration
Anaerobic Respiration
Oxygen required?
yes
no
Glycolysis occurs
yes
yes
ATP yield
38ATP
2ATP
Glucose completely broke down?
yes
no
End products
Carbon dioxide
and water
Lactic acid
Characteristics of the 3 Energy Systems
Energy
System
Aerobic/
Anaerobic
Fuel/
Energy
Source
By-product
Exercise
intensity
Duration
Sporting
Examples
NOTES
ATP/ PC
Anaerobic
ATP/ PC
Creatine
High
(Flat Out)
10 – 15
Seconds
Sprinting,
athletic field
events, weightlifting.
Small muscular
stores of ATP and PC
are exhausted quickly
leading to a rapid
decline in immediate
energy.
Lactic
Acid
Anaerobic
Glycogen
Glucose
Pyruvic Acid/
Lactic Acid
High
Intensity
Up to 3
minutes
400m
800m
Racket sports.
Lactic acid is a byproduct and can
cause rapid fatigue.
Aerobic
Aerobic
Fat/
glucose
mixture
Water/ CO2
Low
3 minutes
onwards
Long distance
running/
cycling.
This system is
limited by
availability of O2