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. 2

Calorie, Joule and Watt Calorie is the amount of heat energy needed to raise the temperature of 1 gram of water through 1 o C. 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. 3

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. 4

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 5

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

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)

Pi adenosine Pi + Energy released to do work ATP ADP Enzymes adenosine 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. 11

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. 12

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 14

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. 15

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. 16

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. 18

glycolysis takes place as it does not require oxygen in absence of oxygen pyruvic acid is turned into lactic acid. pyruvic acid lactic acid glucose 2 ADP + 2 Pi 2 ATP

ADENOSINE TRIPHOSPHATE (ATP) Formed in the breaking down ofGLUCOSE 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 +

Outline of Lactic Acid System (anaerobi glycolysis) Production of energy for resynthesis of ATP 21

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 O 2 Pyruvic acid is removed when O 2 is available BUT: No O 2 = Pyruvic acid is converted into lactic acid Muscles fail to contract fully - fatigue

The lactic acid builds up due to the shortage of O 2 = 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. 24

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 O 2 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 O 2 to allow effective aerobic respiration. 26

glucose + OXYGEN energy + carbon dioxide + water (to make ATP)

Aerobic respiration happens in stages: Stage 1 – Glycolysis glyco lysis glucose splitting

In glycolysis, a glucose molecule is broken down into pyruvic acid. energy released to make small quantity of ATP (2 molecules) series of enzyme controlled reactions pyruvic acid glucose 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 O 2 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. 30

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.

energy released to make large quantity of ATP (36 molecules) series of enzyme controlled reactions pyruvic acid 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. 33

The Kreb’s Cycle. The pyruvic acid is taken by the enzyme acetyl CoA into the Kreb’s cycle in the mitochondria Glycogen Pyruvic acid 2 ATP Lactic acid Kreb’s cycle *Sarcoplasm* *Mitochondria* 2 ATP 2CO 2 Removed via lungs Acetyl CoA

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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 O 2 (aerobic respiration)

The H 2 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 O 2 and H 2 to form water (H 2 0). 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. 37

Electrons move in steps from carrier to carrier downhill to O 2

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Creatine phosphate and stored ATP– first few seconds Creatine phosphate and stored ATP – first few seconds Glycolysis– after 8-10 seconds Glycolysis – after 8-10 seconds Aerobic respiration–after 2-4 min of exercise Aerobic respiration –after 2-4 min of exercise Repayment of oxygen debt– lactic acid converted back to pyruvic acid, rephosphorylation of creatine 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? yesno Glycolysis occurs yesyes ATP yield 38ATP2ATP Glucose completely broke down? yesno 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/ PCAnaerobicATP/ PCCreatineHigh (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 Glycogen Glucose Pyruvic Acid/ Lactic Acid High Intensity Up to 3 minutes 400m 800m Racket sports. Lactic acid is a by- product and can cause rapid fatigue. Aerobic Fat/ glucose mixture Water/ CO 2 Low3 minutes onwards Long distance running/ cycling. This system is limited by availability of O 2