Review of Bioenergetics SP5005 Physiology Alex Nowicky power point slides: Powers and Howley- Exercise Physiology Ch 3 and 4
What is bioenergetics? • Study of energy in living systems • what it is? • Where does it come from? • How is it measured? • How is it produced and used by human body at rest and during exercise? • Part of science of biochemistry -studies conversion of matter into energy by living systems
For your own study use any ex physiology text and cover the following: • Energy sources • recovery from exercise • measurement of energy, work and power • This lecture is an overview of these!
Aim: review energy metabolism Learning outcomes • ATP is central to all energy transactions • Oxidation (O2) (in mitochondria) central • define aerobic and anaerobic pathways - systems of enzymes and their regulation • fate of fuels - CHO, fats and proteins- relative yields of useful energy (ATP)
Learning outcomes (con’t) • role of glycogenolysyis, -oxidation, gluconeogenesis • indirect calorimetry for monitoring energy expenditure- oxygen consumption- (RER) • contribution of fuel supply during exercise (short vs. long duration) • role aerobic and anaerobic systems during exercise and recovery
Metabolism • Total of all chemical reactions that occur in the body • Anabolic reactions • Synthesis of molecules • Catabolic reactions • Breakdown of molecules • Bioenergetics- oxidation (O2) • Converting foodstuffs (fats, proteins, carbohydrates) into energy
Cellular Chemical Reactions • Endergonic reactions • Require energy to be added • Exergonic reactions • Release energy • Coupled reactions • Liberation of energy in an exergonic reaction drives an endergonic reaction
Enzymes • Catalysts that regulate the speed of reactions • Lower the energy of activation • Factors that regulate enzyme activity • Temperature (what happens with changes in T?) • pH ( what happens with changes in pH?) • Interact with specific substrates • Lock and key model
Fuels for Exercise • Carbohydrates • Glucose • Stored as glycogen in liver and muscle • Fats • Primarily fatty acids • Stored as triglycerides- adipose tissue and muscles • Proteins • Not a primary energy source during exercise
ATP ADP + Pi+ Energy ATPase High-Energy Phosphates • Adenosine triphosphate (ATP) • Consists of adenine, ribose, and three linked phosphates • Formation • Breakdown ADP + Pi ATP
Carbohydrate w Readily available (if included in diet) and easily metabolized by muscles wIngested, then taken up by muscles and liver and converted to glycogen w Glycogen stored in the liver is converted back to glucose as needed and transported by the blood to the muscles to form ATP
Fat (triglycerides) w Provides substantial energy during prolonged, low-intensity activity- light weight (little water in storage) w Body stores of fat are larger than carbohydrate reserves w Less accessible for metabolism because it must be reduced to glycerol and free fatty acids (FFA) w Only FFAs are used to form ATP- triglycerides- must be broken down by process of lipolysis
Protein - Body uses little protein during rest and exercise (less than 5% to 10%). w Can be used as energy source if converted to glucose via glucogenesis (or gluconeogenesis) w Can generate FFAs in times of starvation through lipogenesis • w Only basic units of protein—amino acids—can be used for energy- via transamination feed into Kreb’s cycle • waste produce is ammonia - must be excreted (as urea)
Oxidation of Fat- FFA via - oxidation w Lypolysis—breakdown of triglycerides into glycerol and free fatty acids (FFAs). w FFAs travel via blood to muscle fibers and are broken down by enzymes in the mitochondria into acetyl CoA. w Acetyl CoA enters the Krebs cycle and the electron transport chain. w Fat oxidation requires more oxygen and generates more energy than carbohydrate oxidation.
What Determines Oxidative Capacity? w Oxidative enzyme activity within the muscle w Fiber-type composition and number of mitochondria w Endurance training w Oxygen availability and uptake in the lungs
Bioenergetics • Formation of ATP • Phosphocreatine (PC) breakdown • Degradation of glucose and glycogen (glycolysis) • Oxidative formation of ATP • Anaerobic pathways • Do not involve O2 • PC breakdown and glycolysis (lactate) • Aerobic pathways- only occur in mitochondria • Electron transport system (ETS) -Requires O2 • Oxidative phosphorylation
PC + ADP ATP + C Creatine kinase Anaerobic ATP Production • ATP-PC system • Immediate source of ATP • Glycolysis • Energy investment phase • Requires 2 ATP • Energy generation phase • Produces ATP, NADH (carrier molecule), and pyruvate or lactate
ATP AND PCr DURING SPRINTING What does this show?
Oxidation-Reduction Reactions • Oxidation • Molecule accepts electrons (along with H+) • Reduction • Molecule donates electrons • Nicotinomide adenine dinucleotide (NAD) • Flavin adenine dinucleotide (FAD) NAD + 2H+ NADH + H+ FAD + 2H+ FADH2
Production of Lactic Acid • Normally, O2 is available in the mitochondria to accept H+ (and electrons) from NADH produced in glycolysis • In anaerobic pathways, O2 is not available • H+ and electrons from NADH are accepted by pyruvic acid to form lactic acid
Aerobic ATP Production • Krebs cycle (citric acid cycle) • Completes the oxidation of substrates and produces NADH and FADH to enter the electron transport chain • Electron transport chain • Electrons removed from NADH and FADH are passed along a series of carriers to produce ATP • H+ from NADH and FADH are accepted by O2 to form water
Glycogen Breakdown and Synthesis Glycolysis—Breakdown of glucose; may be anaerobic or aerobic Glycogenesis—Process by which glycogen is synthesized from glucose to be stored in the liver Glycogenolysis—Process by which glycogen is broken into glucose-1-phosphate to be used by muscles Gluco(neo)genesis- formation of glucose from lipids and proteins via intermediates (lactate, pyruvate, amino acids)
Summary- Oxidation of Carbohydrate 1. Pyruvic acid from glycolysis is converted to acetyl coenzyme A (acetyl CoA). 2. Acetyl CoA enters the Krebs cycle and forms 2 ATP, carbon dioxide, and hydrogen. 3. Hydrogen in the cell combines with two coenzymes that carry it to the electron transport chain. 4. Electron transport chain recombines hydrogen atoms to produce ATP and water. 5. One molecule of glycogen can generate up to 39 molecules of ATP.
Summary (con’t) - Oxidation of Fat w Lypolysis—breakdown of triglycerides into glycerol and free fatty acids (FFAs). wFFAs travel via blood to muscle fibers and are broken down by enzymes in the mitochondria into acetic acid which is converted to acetyl CoA. w Acetyl CoA enters the Krebs cycle and the electron transport chain. w Fat oxidation requires more oxygen and generates more energy than carbohydrate oxidation.
Stop for 10 min break Any questions?
Kilocalorie and other units (SI) w Energy in biological systems is measured in kilocalories. w1 kilocalorie is the amount of heat energy needed to raise 1 kg of water 1°C at 15 °C. 1kcal= 1000cal Work - energy - application of force through a distance Should be using SI units 1 Joule (J) = 1 N-m/s2 1 kg-m = 1kg moved through 1 metre 1kcal = 426 kg-m = 4.186kiloJoules (kJ) 1 kJ = 0.2389 kcal ( 1kcal = 4.186kJ) 1 litre of O2 consumed = 5.05kcal= 21.14 kJ (1ml of oxygen = .005kcal) - useful conversion factor
Power to perform uses up energy- how much oxygen consumption to supply energy? Power - work/time (Watts or hp) 1hp = 745 watts= 10.7kcal/min 1L of oxygen/min consumption= 5.05kcal/min= 21 kJ/min 1MET = 3.5ml oxygen/kg/min= 0.0177kcal/kg/min 15 kcal/min= ? Oxygen/min (can you do this?)
CARBOHYDRATE vs FAT 1 gram of CHO--> 4 kcal 1 gram of FFA (palmitic acid)--> 9 kcal
g kcal Carbohydrates grams kcal Liver glycogen 110 451 Muscle glycogen 250 1,025 Glucose in body fluids 15 62 Total375 1,538 Fat Subcutaneous 7,800 70,980 Intramuscular 161 1,465 Total7,961 72,445 Note. These estimates are based on an average body weight of 65 kg (143 lb) with 12% body fat. Body Stores of Fuels and Energy
Oxygen consumption for Carbohydrate (glucose from glycogen) (C6H1206)n + 6 O2 --> 6 CO2 +6 H20 + 39 ATP 6 moles of O2 needed to break down 1 mole of glycogen 6 moles x 22.4 l/mole oxygen = 134.4 l 134.4l/39 moles of ATP = 3.45 l/mole ATP at rest takes about 10-15 min, during max exercise takes about 1 min ratio (RQ) carbon dioxide/oxygen = 6/6 = 1
Aerobic ATP yield from FFA (free fatty acid - palmitic acid (16C) 16C 7 Acyl coA 7 acetyl coA (C16H3202) + 23 O2 --> 16 CO2 +16 H20 + 130 ATP 23 moles of O2 needed to break down 1 of palmitic acid 23 moles x 22.4 l/mole oxygen = 512.2 l 512l/130 moles of ATP = 3.96 l O2/mole ATP ratio of carbon dioxide/oxygen = 16/23 = 0.7 15% more oxygen than metabolising glycogen, but advantage is light weight (little water) storage
How do we determine efficiency of ox phos- respiration (metabolism of glucose)? • Efficiency = 38moles ATP x 7.3kcal/mole ATP 686 kcal/mole glucose = 0.4 x100% = 40% (60% lost heat) how does this compare to mechanical engine?
Control of Bioenergetics • Rate-limiting enzymes • An enzyme that regulates the rate of a metabolic pathway • Levels of ATP and ADP+Pi • High levels of ATP inhibit ATP production • Low levels of ATP and high levels of ADP+Pi stimulate ATP production • Calcium may stimulate aerobic ATP production
Interaction Between Aerobic and Anaerobic ATP Production • Energy to perform exercise comes from an interaction between aerobic and anaerobic pathways • Effect of duration and intensity • Short-term, high-intensity activities • Greater contribution of anaerobic energy systems • Long-term, low to moderate-intensity exercise • Majority of ATP produced from aerobic sources
System moles ATP/min power capacity phosphagen 3.6 0.7 anaerobic glycolysis 1.6 1.2 aerobic (from glycogen) 1.0 90.0 at rest - aerobic system supplies ATP with oxygen consumption about 0.3L/min, blood lactate remains constant Maximal capacity and power of three energy systems