ENERGY SYSTEMS RECAP NOTES -

  • ENERGY DEFINITIONS -

    • ENERGY -

      • energy is that capacity to do work, and work has a mechanical definition ( work = force x distance ) moved in the direction of the force, energy and work are measured in joules

    • CHEMICAL ENERGY -

      • is energy produced from a series of complex chemical reactions which can then be made available as kinetic energy and potential energy, for example chemical energy in the stored form of ATP is the most useful form of energy in living systems because its used to run almost all functional processes

    • all chemical reactions either give out energy ( exothermic ) or take in energy ( endothermic )

    • the biological energy system works cleverly to take in energy in the form of fuel or food, and then transfer it into a different type of energy in order to be used for respiration

    • KINETIC ENERGY -

      • is energy due to the movement or motion of an object , observed by the constant moving of an object or living thing EG by a person running

    • POTENTIAL ENERGY -

      • is stored energy that has the potential or capacity to do work, but is not presently doing so EG when your seated, your leg muscles hold potential energy that’s then converted to kinetic when you stand up in order to produce movement

    • MECHANICAL ENERGY -

      • is energy directly produced by forces which do work in moving matter, EG when riding a bike, your legs provide the mechanical energy for moving the pedals, which propels movement forward

    • ELECTRICAL ENERGY -

      • results from the movement of charged particles, in humans electrical currents are produced by the movement of charged ions across or along cell membranes, or the nervous system uses them to transmit messages between body parts

    • POWER -

      • power is the rate at which energy is used or the energy used per second which is measured in watts

      • it can be calculated using the formula

      • power (w) = energy (j)

        ——————————-

        time (s)

  • ENERGY TRANSFER IN THE BODY -

    • we derive our energy from food, namely carbohydrates, fats and proteins

    • the energy derived from them is stored in bodily tissue in the form of a high energy compound called adenosine triphosphate (ATP) which can be generated through three different processes -

      • ATP-PC system (AKA alactic anaerobic system)

      • Anaerobic glycolytic system (AKA lactic acid anaerobic system)

      • Aerobic system

  • ATP = ADENOSINE TRIPHOSPHATE -

    • the compound which stores energy and is therefore the energy currency which is linked to the intensity and duration of physical activity

    • ATP is found in every living tissue and and its breakdown provides energy for all life processes

    • EG the function of the liver and muscular contraction

    • the energy released during tissue respiration is stored in the chemical bonds in ATP and so this energy is released ( an exothermic reaction )

    • resynthesis of ATP from ADP ( adenosine diphosphate ) is an endothermic since energy is given to the molecule to enable the reaction to happen, this energy is derived from food fuels

  • ANEROBIC ENERGY SYSTEMS -

  • THE ATP-PC SYSTEM -

    • this system of replenishing of ATP from ADP is the predominant one for activity which lasts between 3 and 10 seconds, for the highest intensity work

    • no oxygens needed, its anaerobic

    • the chemical reaction within this system is a coupled reaction in which ATP is resynthesized via the molecule phosphocreatine (PC) which is stored in the muscle sarcoplasm

    • the following reactions take place:

      • PC = P + C + ENERGY

      • ENERGY + ADP + P = ENERGY

    • the two reactions are facilitated by the enzyme creatine kinase (CK)

    • the net effect of these reactions are:

      • PC + ADP = ATP + C

    • PC is re-created in muscle cells during the recovery process which requires energy and is an endothermic reaction

    • during intense exercise, peak anaerobic power is attained in the first 5 seconds and depletion of PC stores occurs between 7 and 9 seconds

    • this causes PC levels to fall to zero by 10 seconds and the capacity to maintain ATP resynthesis at this point depends on the lactic acid and aerobic system

  • THE ANAEROBIC GLYCOLYTIC SYSTEM / LACTIC ACID SYSTEM -

    • glycolysis is anaerobic and takes place in the muscle cell sarcoplasm

    • the steps of it are:

      • carbs from the food we eat are stored as glycogen in the liver tissue

      • glycogen is transferred to glucose using the hormone glucagon that’s released when blood glucose levels fall

      • the breakdown of glucose provides energy to resynthesise ATP from ADP, this is facilitated by the enzymes phosphofructokinase (PFK) and glycogen phosphorylase (GPP)

      • this process produces pyruvic acid, which is then transferred to lactic acid using the enzyme lactate dehydrogenase (LDH)

      • rapid glycolysis allows ATP to form quickly without oxygen, and produces enough energy to rebuild 2 ATP molecules from 1 molecule of glucose

    • as work intensity increases lactic acid starts to accumulate above resting values which produces muscle fatigue and pain, the resultant low PH decreases enzyme active and prevent cross bridge formation in muscles, which subsequently reduces muscle action and performance

    • the lactic acid is predominantly used to resynthesise ATP in sport or activities in which the flat-out effort up to 30-60 seconds

    • after exercise stops, excess oxygen is taken in to transfer lactic acid back into pyruvic acid, this is called the excess post-exercise oxygen consumption (EPOC)

  • THE AEROBIC ENERGY SYSTEM -

    • the aerobic system releases stored energy from carbohydrates, fats and proteins

    • the aerobic system relies on the presence of oxygen to completely break down stored energy into carbon dioxide, water and energy

    • the energy yield is very high, 1 molecule of glucose yields 36 molecules of ATP , this process will happen indefinitely until energy stores run out

    • the stages are:

      • GLYCOLYSIS -

        • glycolysis happens the same way it does in the lactic acid system in the muscle cell sarcoplasm

        • glycogen to glucose using glucagon, then glucose transfers to pyruvic acid using the PFK and GPP enzymes

        • glycolysis produces 2 molecules of ATP

      • KREBS CYCLE -

        • this stage happens in the presence of oxygen in the matrix of the muscle cell mitochondria

        • the two molecules of pyruvic acid combine with oxaloacetic acid and acetyl co enzyme A to form citric acid in the Krebs cycle

        • the citric acid is then oxidised as the hydrogen is removed from this compound to be used in the next stage

        • carbon and oxygen are left which are removed as CO2 through the lungs

        • enough energy is released here to resynthesise 2 ATP molecules

        • free fatty acids and proteins can also be used to resynthesise ATP molecules when carbohydrate glycogen stores run out

      • THE ELECTRON TRANSPORT CHAIN -

        • the electron transport chain occurs in the presence of oxygen within the cristae of the mitochondria in the muscle cells

        • the hydrogen given off at the Krebs cycle are carried to the electron transport chain by the electron carriers FADs and NADs

        • its then split into hydrogen ions (H+) and electrons ( e-)

        • during a series of reactions the hydrogen ions are oxidised to produce water (H2O) and the electrons provide the energy to resynthesise ATP

    • in summary the total effect of aerobic respiration is that it is an endothermic reaction:

    • GLUCOSE + 36 ADP + 36P + 6CO2 + 36ATP + 6H20

    • fat fuels produce 2 ATPs less per molecule of glucose