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Bioenergetics VIDEO SEGMENT ONE: OVERVIEW - Chemical energy enters the body as carbohydrates, fats and proteins, which are comprised of glucose molecules, fatty acids and amino acids, respectively o The body uses these substrates to produce ATP - The od s e erg urre o Utilises chemical energy sources a.k.a foodstuffs to combine ADP and Pi facilitated by ATPsynthase to produce ATP by products of heat, CO2 and water also produced o ATPase (enzyme) is then able to break ATP down to release this energy ATP breakdown and synthesis is constantly occurring, however when we exercise, as our demand for energy increases, so too does the rate of ATP synthesis and breakdown o This is why core temperature increases when we exercise, as a result of the increased heat production Cells also a t store ATP, hi h is h e ha e to ake it there a d the he de a d increases ATP - ENZYMES - - - Biological catalysts that increase the rate of a reaction (a.k.a increases the rate at which a substrate becomes a product) o Without enzymes reactions would occur too slowly to maintain life and we would die Metabolic pathways are chains of reactions facilitated by enzymes in which the product of one reaction becomes the substrate for the next o Rate limiting enzymes are generally present at the start of a metabolic pathway and control the rate at which reactions occur In the case of ATP production, large amounts of ATP being present will inhibit the action of the rate limiting enzyme, whilst a low amount of ATP will cause the rate to increase Temperature affects enzymes as with all protein structures o A slight increase above normal body temperature increases the productivity of enzymes This is due to higher te peratures ausi g parti les to o e arou d faster, thus the re more likely to combine with the enzyme o Above about 40 degrees, enzyme function drastically decreases as the active site of the enzyme denatures, breaking down the tertiary structure of the protein OXIDATION-REDUCTION REACTIONS - OIL RIG : oxidation is losing , reduction is gaining o Refers to the losing or gaining of electrons/ hydrogen atoms NAD and FAD o Coenzymes- a t as h droge ta is taki g h droge s fro o idatio rea tio s a d deli er the reduction reactions FAD will become FADH2 NAD will become NADH for VIDEO SEGMENT TWO: OVERVIEW OF ANAEROBIC AND AEROBIC METABOLISM Anaerobic - Uses GLUCOSE as a chemical source for ATP production o Occurs in the absence of oxygen o Two anaerobic systems: ATP-PC and anaerobic glycolysis o Takes pla e i the ell s toplas Aerobic - Uses GLUCOSE, FATTY ACIDS and AMINO ACIDS to produce ATP o Can only occur in the presence of oxygen o Occurs in the mitochondria Rest to exercise - ATP-PC system provides the first bit of energy Anaerobic glycolysis is then predominant for the next few minutes Aerobic respiration then takes over and generally remains predominant for the duration of the exercise VIDEO SEGMENT THREE: ANAEROBIC METABOLISM ATP-PC system - - The most rapid in producing ATP o Predominant at the onset and up until the first 5 seconds into the exercise Utilises phosphocreatine (stored in the muscles) to donate the phosphate, creating ATP o Creatine kinase facilitates this reaction o Creatine supplementation is thought to help as it increases available creatine which can combine with Pi for greater levels of PC storage BENEFITS: quick ATP production DISADVANTAGES: finite capacity that last only a few seconds Anaerobic glycolysis - - The intermediate ATP production pathway o Predo i a t fro arou d 5 se o ds up til 2 i utes of exercise Occurs in the cytoplasm of the cell (not in mitochondria) Can only utilise GLUCOSE as a chemical energy source o Glucose is broken down into two pyruvate molecules, which releases H+ (taken up by NAD) NADH then provides the energy to convert pyruvate to lactic acid and a net gain of 2 ATP results VIDEO SEGMENT FOUR: AEROBIC METABOLISM Stage one: glycolysis - Same process as with anaerobic glycolysis, however rather than become lactic acid, pyruvate (as well as the NADH it has oxidised) travels to the matrix of the mitochondria o Net gain of 2 ATP 2 NADH 2 Acetyl Co-A molecules Stage two: the Krebs/citric acid cycle - Functions to complete oxidation of Acetly Co-A (which began in glycolysis) Occurs in the matrix of the mitochondria Each Acetyl Co-A produces; o 3 NADH o 2 CO2 o 1 ATP o 1 FADH2 o So we effectively gain 6 NADH, 4 CO2 , 2 ATP and 2 FADH2 Stage three: electron transport chain - - - Cytochromes in the inner membrane of the mitochondria take the H+ from the FADH2 and NADH o The cytochromes pass the electrons along, using their energy to phosphorylate ADP and Pi to ATP Energy is used to pump the H+ into outer compartment creating a concentration gradient The H+ then diffuses back into the matrix via channels associated with ATPsynthase o This simultaneously facilitates ADP and Pi to form ATP Note that O2 acts as the final electron acceptor from the ETC, combining to form H2O o If oxygen is not present the ETC will thus not occur, hence the name aerobic respiration ATP is then moved out of the matrix via carrier molecules which exchange it for ADP and Pi PHOSPHORYLATION - Direct/Substrate: ATP produced directly from glycolysis/krebs cycle Oxidative: ATP produced from ADP and Pi being combined from energy of ETC Aerobic respiration thus provides us with a total of 32 ATP per molecule of glucose - Important to note that approximately 80% of this energy is released as heat VIDEO SEGMENT FIVE: GLUCOSE AND ENERGY Glucose sources - Muscles can obtain glucose from o Exogenous sources : sources outside the body o Liver glycogen stores: glucose is stored as glycogen in the liver (and in small amounts in the muscle) o Gluconeogenesis: production of glucose by the liver from non-carbohydrate sources Glycogenolysis - The breakdown of glycogen to glucose in the liver o Glucose is then released into blood where it can be used Glycogenesis - Building glycogen from glucose o When the body has a surplus of glucose, the liver will convert it to glycogen for storage These glycogen stores are depleted after a few hours of exercise Gluconeogenesis - The production of glucose from sources other than glycogen o Amino acids: converted to lactic acid, then undergoes reverse glycolysis o Glycerol: (head of fatty acids) converted to intermediate, then undergoes partial reverse of glycolysis o Lactic acid: reverse glycolysis Cori cycle - Circular pathway of lactic acid between the muscles and the liver o Goes from skeletal muscles via blood to liver for breakdown Undergoes reverse glycolysis to produce glucose Glucose sent back to muscles via blood for use VIDEO SEGMENT SIX: LIPIDS, PROTEIN & ENERGY Lipolysis - Breakdown of triglycerides in adipose tissue and skeletal muscle o Broken into glycerol head and fatty acid tails The fatty acid tails contain lots of H+, thus are very energy dense Lipogenesis - The formation of fat in adipocytes o A major form of energy storage in the body When excessive glucose of amino acids are taken in, the body converts them to Acetyl Co-A and then utilises it to produce fatty acids Beta oxidation - Occurs in the matrix o Fatty acids are broken down through removal of carbons Every two carbon molecules removed results in the formation of one Acetly Co-A, one FADH2 and one NADH Aerobic metabolism of lipids - FADH2 and NADH from beta oxidation deliver electrons to ETC Acetly Co-A enters krebs cycle A total of 108 ATP are produced per 16 carbon long fatty acid tail Aerobic metabolism of proteins - Protein is broken down into amino acids o Then converted to pyruvic acid Then converted to Acetyl Co-A o Krebs cycle intermediates are also produced VIDEO SEGMENT SEVEN: SPORTING EVENTS AND AEROBIC/ANAEROBIC CONTRIBUTIONS Aerobic ATP production - After 2-3 minutes, 50% of ATP comes from aerobic breakdown At around 10 minutes, 90% of ATP is being produced aerobically SHORT TERM EXERCISE OF HIGH INTENSITY= anaerobic LONG TERM EXERCISE OF LOW TO MODERATE INTENSITY = aerobic