ATP ENERGY PRODUCTION

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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

• Energy release in the body is complicated.• There is only one usable form of energy in the

body – adenosine triphosphate (ATP).• All food we eat has to be converted into ATP.• 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

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• When a compound is broken down( the bonds between the molecules are broken) the energy is released.

• ATP is broken down to adenosine diphosphate (ADP) and free 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• Once ATP has been broken down to release energy it has

to be put back.• There are three ways that this is achieved in the human

body:• 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 and 2 are anaerobic they take place without

oxygen• System 3 is aerobic: it requires oxygen to work.

The ATP Molecule

Adenosine

Adenosine

Energy

Adenosine Triphosphate (ATP)

The breakdown of ATP:

PP

P

PP P

ATP = ADP + energy for biological work + P

(ADP = Adenosine Diphosphate)

Energy for cellular function

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ATP Production by Phosphocreatine or Alactic System

• Phosphocreatine is a high- energy phosphate compound.

• It is found in the sarcoplasm of the muscle.• Potential energy is stored in the bonds of the

compound. Phosphocreatine → P+ Creatine + Energy creatine kinase

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• Creatine kinase is activated when the level of ADP in the muscle cell increases.

• It is when the stores of ATP start to diminish.• 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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• This is the only system capable of producing ATP quickly.

• During activities that demand large amounts of energy over a short period of time

• As PC is stored in the muscle it is readily accessible as an energy source.

• Energy for ATP can be obtained extremely quickly.

• 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.• The energy needed comes from the food we

eat.• It involves the partial breakdown of glucose.• Breakdown of PC does not rely on the

availability of oxygen.• It is much more complex than Phosphocreatine.• It therefore stores more energy.

The Glycolytic System

•Involves the breakdown (lysis) of glucose by glycolytic

enzymes.

•Glucose comes from the digestion of carbs & breakdown of

glycogen during glycogenolysis.

•Glycogen is made from glucose during glycogenisis.

•Glycolysis produces pyruvic acid which is then converted to

lactic acid in the absence of oxygen.

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• Glucose is broken down anaerobically (in absence of oxygen).

• Because there is no O2 lactic acid is formed.• Breakdown of bonds in glucose release

energy.• The energy is used to synthesise ATP.• The lactic acid system takes longer to produce

energy than the ATP/PC system.• It supplies energy for high intensity activities

for about a minute.• The 400m is a good example.

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Outline of Lactic Acid System (anaerobi glycolysis)Production of energy for resynthesis of ATP

ADENOSINE TRIPHOSPHATE (ATP)

Formed in the breaking down of GLUCOSE

This in turn is broken down by a chemical reaction to give

PYRUVIC ACID

If there is insufficient oxygen LACTIC ACID accumulates

This causes FATIGUE in the muscles. & H+

LACTIC ACID SYSTEM

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 easily removed when O2 is available

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.

Accumulation of Lactic Acid

Lactic acid affects muscular contraction by:

1. Inhibiting the secretion of calcium that enables the

coupling of actin and myosin protein filaments = protein

filaments cant attach to each other. The sliding of the muscle

protein filaments = not possible.

2. Inhibiting the action of the glycolytic enzymes = glucose not

being broken down. Glucose is the food fuel for both

anaerobic and aerobic glycolysis.

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Fatigue • When glycogen is broken down anaerobically

lactic acid is produced.• If lactic acid accumulates it lowers the pH (H+).• pH affects action of phosphofructokinase.• It also affects lipoprotein kinase that breaks

down fat.• The body’s ability to synthesise ATP is

temporarily reduced causing fatigue.

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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 2 anaerobic systems are used.• As heart rate and rate of ventilation increase

more oxygen gets to the working muscles.• Within 1-2 minutes the muscles are being

supplied with enough O2 to allow effective aerobic respiration.

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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: 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.

The Kreb’s Cycle.• The pyruvic acid is taken by the enzyme acetyl

CoA into the Kreb’s cycle in the mitochondria

Glycogen

Pyruvic acid2 ATP

Lactic acid

Kreb’s cycle

*Sarcoplasm*

*Mitochondria*

2 ATP2CO2 Removed via lungs

Acetyl CoA

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Stage 3:The Electron transport chain/electron transport system

• The H2 atoms removed in stage 2 are transported by coenzymes to the inner membrane of the mitochondria.

• The electrons are passed along by electron carries combining with O2 and H2 ions to form water.

• Energy is released which combines ADP with phosphate to form ATP.

• The energy yield from the electron transport chain forms 34 molecules of ATP.

• The total yield of ATP from aerobic respiration is therefore 38 molecules of ATP.

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• The aerobic system of synthesising ATP is the most efficient.

• The byproducts (CO2 and H2O) are easily expelled from the body.

• However the reactions involved in this system depend on the availability of O2.

Electron transport chain

• Involves water (perspiration), heat and large amounts of ATP being released.

• Aerobic system breaks down carbs rather than fats to release energy (fats produce more ATP than carbs but require more O2 to produce equivalent amount of ATP.)

• Aerobic system is fatigue resistant = primary source of ATP for endurance activities.

• Aerobic production of ATP happens in the mitochondria.

The ETC.

Krebs cycle

Hydrogen

ETC

O2

H2O34ATP

Mitochondria matrix.

Mitochondria cristae

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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, weight-lifting.

Small muscular stores of ATP and PC are exhausted quickly leading to a rapid decline in immediate energy.

Lactic Acid

Anaerobic GlycogenGlucose

Pyruvic Acid/ Lactic Acid

High Intensity

Up to 3 minutes

400m800mRacket sports.

Lactic acid is a by-product 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