UNIT 3: PHYSICALACTIVITY PARTICIPATIONAND PHYSIOLOGICALPERFORMANCE
FOOD FUELS AND THE ENERGY SYSTEMSArea of Study 2 - Physiological Responses to Physical Activity
Food Fuels The food we eat refuels the three energy systems. Carbohydrates (CHO) Pasta Breads Cerea lCarbohydrates are thepreferred source of energyduring exercise as theyrequire less 02to be broken Fruit &down. Vegetable
Fats Fats are the body’s mainOil Fatty meat source of fuel at rest and during prolonged submaximal exercise. Require more 02 than carbohydrates to be broken down. Milk & cheese Butter Nuts
Protein Legumes and grainsLeanmeat Poultry Eggs Used mainly for growth and repair. Fish
Food Types, Fuel Conversions and Storage Food Fuel Recommended Food Fuel Storage Daily Intake (%) following DigestionCarbohydrate 55 – 60 Glucose Glycogen – muscles and liverFats (Triglycerides) 25 – 30 Free fatty acids Adipose tissue at various sitesProtein 10 – 15 Amino acids As muscle at various sites
Energy for Muscle Contraction Energy for muscular contractions comes from splitting of a high energy compound called Adenosine Triphosphate (ATP) which is stored in very small amounts in the muscles. Once it is depleted it is quickly replaced by the three energy systems.
ATP Breakdown and Energy Release ADENOSI P P P Adenosine NE Triphosphate ADENOSI P P P Adenosine Diphosphate NEThe three energy systems break down fuel stores releasing energy for the resynthesis o ADENOSI P P P Adenosine NE Triphosphate
Energy Systems The body has three different ATP producing systems or pathways:- ANAEROBIC SYSTEMS (without 02 ) ATP-CP system – also called alactacid, creatine phosphate or phosphogen system. Anaerobic Glycolysis – also called lactic acid system or lactacid system AEROBIC SYSTEM (with 02 ) AerobicGlycolysis – breakdown of carbohydrates Anaerobic Lipolysis – breakdown of fats
Contribution of Systems to EnergyProduction At rest the demands for ATP are low and an be met aerobically. At the onset of exercise the demand for ATP increases rapidly – as oxygen uptake can’t rise rapidly enough to meet the demand for ATP the body calls on the anaerobic systems to meet the energy shortfall. It should be noted that all three energy systems are activated at the start of exercise – the contribution of each is determined by the intensity and duration of exercise.
ATP – CP System Chemical fuel – creatine phosphate No 02 required Fastest energy production as simple chemical reactions involved in breakdown Can supply energy for up to 10secs Relative ATP production – few; very limited The more intense the activity the more rapidly CP stores are depleted After 5secs of maximal activity CP stores are 50% depleted and the lactic acid system becomes the major contributor
Creatine Phosphate Creatine is made: by the body (from amino acids arginine, glycine and methionine) gained from the diet - occurs naturally in meats and fish Only 120g of creatine is stored in the body – mainly in the muscles. During high intensity exercise, the body allows creatine phosphate levels to decline in order to use it to regenerate ATP Creatine phosphate regenerates during recovery, or when the exercise intensity is low enough that ATP demand in the muscles has decreased to the point the body can use ATP to regenerate creatine phosphate.
Creatine Phosphate CREATINE PHOSPHATE Creatine kinase breaks down creatine phosphate PHOSPHA ENERG TE CREATIN Y E Free creatine can be Free phosphate combines reformed to creatine with creatine to formphosphate or released from creatine phosphate or ADP the cell, processed by the to form ATP. kidneys and excreted in Energy for this process is urine. released from the breakdown of ATP.
Anaerobic Glycolysis Chemical fuel – glycogen (glucose) 02 required – no Speed of breakdown – fast (chemical reactions more complex than ATP/CP system Energy produced – up to 2mins of high intensity activity – peak usually between 15 and 20 seconds. Contributes 40-45% of ATP during 100m sprint Relative ATP production – few; limited (twice as much as provided by ATP-CP system By product – lactic acid (disassociates to lactate + H+.
Anaerobic Glycolysis Repeated high intensity movements completed without rest e.g. Fast passages of play in basketball 1km time trial 400m
Anaerobic Glycolysis GLUCOSE Energy Investment Phase – two ATP molecules are GLYCOGEN Glucose 6 invested to prepare phosphate molecule to be split Fructose 6 NAD bisphosphate NAD Energy Capture Phase – NAD NADH four ATPs and two NADH used to drive the produced per glucosesynthesis NADH NADH molecule of ATP 2 ATP 2 ATP LACTATE PYRUVATE LACTIC H+ ACID
Aerobic System Chemical fuel/s – glycogen (carbohydrates), triglyceride (fats), amino acids (protein) Preferentially breaks down carbohydrates rather than fats to release energy – fats produce more ATP than carbohydrates but have a greater 02 cost (often used during sub-maximal exercise) 02 required – yes Speed – slow – involves a series of complex chemical reactions By products – carbon dioxide/water (non- fatiguing) Also activated at the start of onset of intense exercise – 02 uptake can be as high as 90% in 30-
Aerobic System Cycling (distance) Running (distance) Triathlon
Aerobic Glycolysis GLYCOGEN GLUCOSE ATPAerobic Glycolysis – in Energythe for Energ 2 -3presence of 02 pyruvate y muscle PYRUVATE ATPS contractiois is converted to acetyl ncoenzyme A, the entrymolecule for the Krebs O2 ATP+ Picycle. ACETYL COENZYME A ATP Energ y Energy KREBS CYCLE 36 for muscle ATPS contractio Energ n y ELECTRON ATP+ Pi TRANSPORT CHAIN
Aerobic Lipolysis FATS Lipolysis – metabolic breakdown of triglycerides into free fatty acids and glycerol in muscle cells. GLYCEROL & FREE FATTY ACIDS Beta oxidation – is the process by fatty acids are broken down in the mitochondria to generate acetyl coenzyme A, the entry molecule for ACETYL the Krebs cycle. COENZYME A ATP KREBS CYCLE Energ y Energy for 147 muscle ATPS contractio Energ n ELECTRON y TRANSPORT SYSTEM ATP+ Pi
Krebs Cycle (Citric Acid Cycle) The Krebs cycle is a complex series of chemical reactions that continues the oxidization of glucose and fats. Acetyl coenzyme A enters the Krebs cycle and is broken down in to carbon dioxide and hydrogen allowing more two more ATPs to be formed. Hydrogen combines with two enzymes called NAD (forms NADH) and FAD (forms FADH2) both of which are high energy compounds, and is transported to the Electron Transport Chain.
Electron Transport Chain Hydrogen is carried to the electron transport chain, another series of chemical reactions, and here it combines with oxygen to form water thus preventing acidification. This chain, which requires the presence of oxygen, also produces heat and results in 34 ATPs being formed.