Substrate Utilisation - Lipids and Protein 2 Slides PDF

5/20/20 Readings § McArdle, W.D., Katch, F.I., & Katch, V.L. (2014). Exercise Physiology: Nutrition, Energy and Human Performance 8th Edition. Baltimore, USA: Lippincott, Williams & Wilkins § Ch 1. Carbohydrates, Lipids and Protein pp 18-39 § Ch 6. Energy Transfer in the Body pp 150-159 Learning O...

5/20/20 Readings § McArdle, W.D., Katch, F.I., & Katch, V.L. (2014). Exercise Physiology: Nutrition, Energy and Human Performance 8th Edition. Baltimore, USA: Lippincott, Williams & Wilkins § Ch 1. Carbohydrates, Lipids and Protein pp 18-39 § Ch 6. Energy Transfer in the Body pp 150-159 Learning Outcomes On completion of this topic the student will be able to: § Describe the role, function and recommended intake of lipids (fatty acids) and protein in the body § Describe and classify fatty acids and triglyceride formation § Describe the role of lipids and protein in exercise performance of varying intensity § Define the process of lipolysis § Describe the catabolism process of protein § Describe specific types of muscle fibres including but not limited to slow-twitch oxidative, fast-twitch oxidative glycolytic fibres and glycolytic fibres § Describe the predominance of muscle fibre phenotype in specific athlete cohorts 2 5/20/20 Lipids http://fitchips.com.au/img/why-fc/chips.png Lipids § Umbrella term for: § Fatty Acids § Mono-, di- and triglycerides § Phospholipids § Cholesterol § Dietary Lipids consist of: § Triglycerides ~97% § Phospholipids § Cholesterol 3 5/20/20 Fatty Acid Fatty Acid Gives it its acidic quality Hydrophilic End Attracted to water https://dlc.dcccd.edu/images/biology/lesson3/lauric_acid_structural_model.jpg Carboxyl Group Hydrocarbon Chain Methyl Group Hydrophobic Tail Repel Water 4 5/20/20 Saturated Fatty Acids Single bonds between carbon §“hard fat” § No double bonds make more sites available for hydrogen atoms = saturated with hydrogen § McArdle et al., 8th Ed Figure 1.8 A, p 19 Unsaturated Fatty Acids §Double bonds exist between carbon atoms §Reduces the number of sites available for hydrogen atoms = unsaturated §Monounsaturated = one double bond §Polyunsaturated = >2 double bonds §Very loosely packed = “soft” fats or oils McArdle et al., 8th Ed Figure 1.8 B, p 19 5 5/20/20 Triglyceride Seeley, 10th Ed Figure 2.16, p 43 Triglyceride Formation § Process of Condensation (dehydration) – whereby a water molecule is cleaved off § Process occurs : 1. FFA levels increase due to food ingestion 2. High levels of insulin McArdle et al., 8th Ed Figure 1.10, p 21 th Seeley, 10 Ed Figure 2.16, p 43 6 5/20/20 https://www.youtube.com/watch?v=BVxeeiR7JB0 Structure of a fatty acid (FA) § FA come in many different forms – 7 common FA in the body § Most common – oleic acid, palmitate acid, stearic acid, linoleic acid, palmitoleic acid § A triglyceride can be made up of 3 different FA § Difference is in the number of carbon bonds in the structure – most commonly 16 – 18 carbons but always multiples of 2 (because of how they’re catabolised, as we’ll find out in just a moment) 7 5/20/20 Triglyceride Breakdown § Hydrolysis = catabolism of something using water § In the case of lipids its called Lipolysis McArdle et al., 8th Ed Figure 1.11, p 22 Breakdown of Dietary Lipids https://www.youtube.com/watch?v=BVxeeiR7JB0 8 5/20/20 Absorption of Lipids https://www.youtube.com/watch?v=BVxeeiR7JB0 Lipoprotiens § Water soluble, main avenue for transporting lipids in the blood §High-Density Lipoproteins (HDL) § “Good” Cholesterol § Removes cholesterol from the arterial wall and delivers it to the liver §Low-Density Lipoproteins (LDL) § “Bad” cholesterol § Delivers cholesterol to the arterial wall Seeley, 10th ed, Figure 24.31, p 900 9 5/20/20 https://www.youtube.com/watch?v=BVxeeiR7JB0 Lipid Storage § Generally fats are stored in ADIPOCYTES (fat cells) in the form of TRIGLYCERIDES (also called triacylglycerol) § Adipose tissue § Subcutaneous fat § Abdominothoracic fat = around organs as support and protection § Small amount also stored in muscle cells McArdle et al., 8th Ed Figure 1.14, p 26 10 5/20/20 Lipid Roles 1. Energy Source and Reserve § 3 benefits of lipids being an energy source: Large quantity of energy per unit weight § 1 gram FAT = 9 kCals (e.g. 12,304g x 9 = 110,736 kCal) § Therefore, 9 kCal x 4.18J = 37.62 kJ/gram FAT More than twice the amount of energy compared to CHO § So the average person stores ~462,876 kJ (12,304 g x 38 kJ) McArdle et al., 8th Ed Figure 1.14, p 26 Lipid roles cont. Transports and Stores easily § 1 g of CHO = 2.7 g of water, heavy storage § Hydrophobic Ready source of Fuel § Have sources in plasma and muscle McArdle et al., 8th Ed Figure 1.14, p 26 11 5/20/20 Lipid Ut ilis at ion at diff er ent I nt ens it ies § During rest and light exercise FAT provides 80-90% of energy § As exercise intensity ­­ the percentage contribution of FAT decreases whilst CHO increases § Total absolute energy from FAT remains essentially the same. 25% 50% 80% e.g. total absolute energy from FAT during exercise at 85% is similar to exercise at 25% WHY don’t we use fat during high intensity exercise?? § The process to breakdown triglyceride to glycerol and FAA is too slow McArdle et al., 8th Ed Figure 1.17, p 28 Lipid Ut ilis at ion I nc r eas es wit h Exercise Dur at ion § 80-90% of energy at rest provided by fat § As exercise duration ­­ so does the percent contribution by lipids § Particularly in a glycogen depleted state McArdle et al., 8th Ed Figure 1.6 B, p 16 McArdle et al., 8th Ed Figure 1.16, p 28 12 5/20/20 Exer cise Tr aining M ay I nc r eas e Lipid Ut ilisat ion § Regular aerobic exercise can increase fat catabolism § = decrease in % used by glycogen = glycogen sparing BUT § Doesn’t help with sustaining higher levels intensity, this still requires glycogen McArdle et al., 8th Ed Figure 1.18, p 29 Lipid roles cont. 2. Protection of vital organs § 4% of body’s fat mass protects against trauma 3. Thermal Insulation § Subcutaneous fat § Consider excess fat and the implications in heat? 4. Vitamin Carrier § Source and Transport (taxi) for 4 fat soluble vitamins (A, D, E and K) 5. Hunger Suppressor § 3.5 hrs to digest lipids = delay the feeling of hunger § Consider fat free diets? 13 5/20/20 How much should we eat? No more that 30% of daily intake should be lipids § Less that 10% TDI of that should be saturated, less than 1% TDI trans fats § 70-80% unsaturated § Consider avocado instead of margarine or butter § Energy Release From Lipids 14 5/20/20 Energy production CHO vs. lipids Glucose = C6H12O6 Palmitate = C16H32O2 § Palmitate has almost 3 x as many Carbon and Hydrogen atoms but is not very oxidised § H atoms are the ones that donate electrons that are used to create energy in the ETC F RO M STO RAG E TO ener gy r elease – St ep 1 § Before a triglyceride can be used to create energy it must first be hydrolysed into its constituents § LIPOLYSIS § Triglyceride + 3 H2O = Glycerol + 3 FA § Catalysed by Hormone Sensitive Lipase (HSL) § HSL is stimulated by epinephrine, norepinephrine (together termed the catecholamines) and growth hormone that are released during exercise, this way it is stimulated as soon as you start exercising 15 5/20/20 Triglyceride Breakdown § Process occurs during: 1. Low to mod intensity exercise 2. Low calorie diet 3. Cold stress 4. Prolonged exercise § Once broken down can either; 1. Reform to a triglyceride or 2. Be carried in blood throughout the body to muscle to be broken down to be used as energy https://www.google.com.au/search?hl=en&site=imghp&tbm=is ch&source=hp&biw=1378&bih=929&q=triclycerol+condensati on&oq=triclycerol+condensation&gs_l=img.3...3253.9440.0.96 39.24.12.0.12.0.0.251.1419.26.6.0....0...1ac.1.64.img..6.5.1173.b1zLktPafG4#hl=en&tbm=is ch&q=triglyceride+condensation&imgrc=wlwhsAXvTDCrMM% 3A Review Tr iglycer ide Br eakdown and F or m at ion § Above = triglyceride formation (condensation) § Below – triglyceride breakdown by hydrolysis (the process of lipolysis) McArdle et al., 8th Ed Figure 1.11, p 22 16 5/20/20 STEP 2 - Glycerol § Glycerol is H2O soluble so it will diffuse out of the adipocytes into the plasma § This makes glycerol an indicator of lipolysis in adipose tissue Its fate: 1. Some glycerol will be converted and accepted into glycolysis (Step 5) as 3-phosphoglyceraldehyde (= 19 ATP from a single glycerol) 2. It can also be used to create glucose in the liver via gluconeogenesis however, this role is relatively minor in terms of energy production McArdle et al., 8th Ed Figure 6.17, p 154 F r ee F at t y Acids ( F FA) and Album in § Once the FA are released from glycerol they will diffuse out of the cell PROBLEM… FA aren't water soluble so they cant diffuse into the plasma SOULTION….. ALBUMIN § ALBUMIN is a protein that has an area on its surface that is hydrophobic § FA become FREE FATTY ACIDS (FFA) as they pass out of the cell and are bound to the hydrophobic region on albumin § FFA aren't truly free fatty acids § Albumin is the taxi that will shuttle FFA around the body in the blood to the tissues where they are required for energy production (or storage) http://www.publicdomainpictures.net/pictures/20000/velka/london-taxis.jpg 17 5/20/20 F FA – t r ans por t t o t he m it oc hondr ia § The FA (remember its not free anymore) now has two pathways: http://www.publicdomainpictures.net/pictures/20000/velka/london-taxis.jpg § Once the albumin taxi reaches the muscles, the FFA are released and transported across the cell 1. If the muscle doesn’t require that FA is can recombine with glycerol to be stored in the muscle as a triglyceride 2. If the muscle requires the FA for energy production it will be transported into the mitochondria to be processed T he Cat abolism of F at t y Acids – St ep 3 § Fatty acids enter into Beta-oxidation § Two important events occur; 1. β- oxidation is a cyclic series of steps that will break off pairs of carbon atoms from a FA to be used to form acetylCoA that can then enter the Krebs Cycle 2. Pairs of H are again sent off to the ETC § No ATP is produced directly § Takes place in the mitochondrial matrix § β- oxidation will produce by-products (acetyl-CoA and H+) that will link the process of fat oxidation with those we have already studied (the Krebs cycle and the ETC) McArdle et al., 8th Ed Figure 6.17, p 154 18 5/20/20 https://image.slidesharecdn.com/betaoxidationproteincatabolism-140414150305-phpapp01/95/beta-oxidation-protein-catabolism-9-638.jpg?cb=1397487839 Beta-Oxidation Firstly, § As a FA enters the mitochondria it is combined with co-enzyme A (CoA) to form fatty acyl-CoA § In this process energy from ATP is used to ACTIVATE the FA molecule § So much energy is required that ATP releases energy from 2 Pi bonds and AMP is created CoA AMP ATP FA Fatty acyl-CoA = 2 ATP used 19 5/20/20 Beta-oxidation § During β-oxidation 2-Carbon Acyl units are chopped off the carbon chain of the FA at a time § These are converted into acetyl-CoA which then enters the Krebs cycle § This process will continue until only the last 2-carbon group remains and this final molecule will actually be acetyl-CoA McArdle et al., 8th Ed Figure 6.17, p 154 Beta Oxidation https://bio.libretexts.org/@api/deki/files/8130/Figure_6.11.2.png?size=bestfit&width=657&height=525&revision=1 20 5/20/20 http://www.namrata.co/wp-content/uploads/2015/07/Beta-oxidation-spiral.png https://classconnection.s3.amazonaws.com/838/flashcards/2220838/jpg/asdf-145099F5DB6486DA578.jpg 21 5/20/20 Beta-Oxidation § 1 NADH+H+ and 1 FADH2 are produced for each 2carbon acyl unit that is cleaved from the FA McArdle et al., 8th Ed Figure 6.17, p 154 Beta-Oxidation § The number of cycles needed to break down a FA will depend on the number of carbons in its structure and therefore will change the amount of energy it produces § The number of cycles required to oxidise a FA can be determined by using the equation; n/2 – 1 Where n is the number of carbons in the FA chain 22 5/20/20 Exam ple – Bet a-O x idat ion of Palm it at e Palmitate is a 16 carbon FA – C16H32O2 § Since Palmitate is a 16-carbon FA it will cycle through β- oxidation = n/2 – 1 cycles 16/2 – 1 cycles = 7 cycles § Each cycle through β- oxidation will produce 1 NADH+H+ and 1 FADH2 that will be taken to the ETC = 7 NADH+H+ and 7 FADH2 to go through the ETC Exam ple – Bet a-O x idat ion of Palm it at e § Each cycle of β- oxidation (7) will produce acetyl-CoA plus the final 2 carbon acyl group that is left will actually be acetyl-CoA § = 8 acetyl-CoA produced from Palmitate during β- oxidation § These 8 acetyl-CoA’s will go to the Krebs cycle and onto the ETC to produce energy in exactly the same way as they would if the process was happening with pyruvate produced during glycolysis § REMEMBER, for acetyl-CoA to enter the Krebs cycle there must be sufficient oxaloacetate to accept it into the process. So it is often said that fats burn in a CHO flame McArdle et al., 8th Ed Figure 6.17, p 154 23 5/20/20 Exam ple – Bet a-O x idat ion of Palm it at e § For each acetyl-CoA that enters the Krebs cycle it will produce: § 1 ATP via GTP substrate level phosphorylation § 3 NADH+H+ § 1 FADH2 § REMEMBER that there was 8 Acetyl-CoA’s from the βoxidation of Palmitate so there will actually be § 8 ATP via GTP § 24 NADH+H+ § 8 FADH2 McArdle et al., 8th Ed Figure 6.14, p 149 Exam ple – Bet a-O x idat ion of Palm it at e § All of the NAD+ and FAD carriers will go to the ETC § Direct from β- oxidation § 7 NADH+H+ and 7 FADH2 = (2.5 ATP x 7) + (1.5 ATP x 7) = 28 ATP § From acetyl-CoA produced in βoxidation that is processed in the Krebs cycle § 24 NADH+H+ and 8 FADH2 = (2.5 ATP x 24) + (1.5 ATP x 8) = 72 ATP Kenny et al. 5th Ed Figure 2.10, p 61 § TOTAL = 100 ATP produced from NAD+ and FAD carriers in the ETC 24 5/20/20 O x idat ion of 1 F at t y Ac id – Balance Sheet § Remember that in a triglyceride there are 3 FA. If we presume they were all Palmitate, we have produced 318 ATP from a single triglyceride 25 5/20/20 Since lipid oxidation and β- oxidation rely on the Krebs cycle and ETC, oxygen is ESSENTIAL for the use of lipids as a fuel = AEROBIC METABOLISM https://www.google.com.au/search?q=cycling&rls=com.microsoft:en-AU:IEAddress&rlz=1I7WQIB_enAU535&source=lnms&tbm=isch&sa=X&ved=0ahUKEwih9ZHIwNXKAhXBYaYKHfHdCIwQ_AUIBygB&biw=1282&bih=851#imgrc=uemI5qTkTNfYPM%3A LIPIDS AND EXERCISE § Will supply most of the energy we use at rest and during lowintensity or prolonged endurance exercise § We store 250,000-420,000 kJ (60,000-100,000 kcal) worth of triglycerides, enough to run 25-40 marathons!....think about how long we can survive without food. § However, the rate of supply is slow due to the extended processes involved, particularly in taking lipids from storage and converting them into ATP § Requiring oxygen means that the process can only happen relatively slowly 26 5/20/20 Lipids and Exercise § During high-intensity exercise glycogen is the fuel of choice and lipolysis is inhibited § During low-moderate intensity exercise where the systems can run aerobically, lipids will be the fuel of choice § If exercise continues for > 1 h and glycogen stores start to decline, the importance of lipids will increase substantially McArdle et al., 8th Ed Figure 1.16 and 1.17, p 28 Ketone Bodies § Since a sufficient supply of oxaloacetate from CHO metabolism is required to feed acetyl-CoA from β- oxidation into the Krebs cycle, it is said that “fats burn in a CHO flame” § There can be problems when there is insufficient CHO being processed (e.g. starvation, very prolonged exercise, low CHO diets such as the Atkins diet) § When acetyl-CoA from β- oxidation cant get into the Krebs cycle the liver converts it into metabolites called ketones or ketone bodies McArdle et al., 8th Ed Figure 6.14 p 149 27 5/20/20 Ketone Bodies § Ketone bodies are acidic § If the ketones aren’t used (i.e. if you aren’t exercising) then they accumulate (remember theses are acidic) and creates a condition called ketosis § A decrease in pH of bodily tissues will affect function § Side Effects § Bad breath (acetone) § Low energy § Impaired mental function Protein 28 5/20/20 https://upload.wikimedia.org/wikipedia/commons/3/32/Lego_Color_Bricks.jpg Proteins Protein = amino acid + peptide bonds § Amino acids are the of proteins § 20 different amino acids required by the body § Essential amino acids – 8 amino acids the body cannot synthesize § Non-essential amino acids – the body can synthesise them § 10-12 kg of Protein (6-8 kg in muscle) § 1 gram = 16.736 kJ of energy (same as CHO) § McArdle et al., 8th Ed Figure 1.19, p 30 Making a Protein = Condensation ¡ Proteins are a series of amino acids – process of condensation (removing of water molecule) joins amino acids together https://qph.ec.quoracdn.net/main-qimg-1b4f8ebc931577a4255f2975e4bd32fc 29 5/20/20 Br eakdown of Pr ot ein t o Am ino Acids = Hyd ro l ysi s https://bam.files.bbci.co.uk/bam/live/content/z7vjtfr/large 2 amino acids joined 2 singular amino acids with H2O added Role of Proteins §Muscle contraction (actin and myosin) §Structural (hair, nails, skin, bones, tendons and ligaments) §Enzymes §Transport (FAD, and NAD, haemoglobin, albumin) §Hormonal Systems (epinephrine, norepinephrine) §Assists in blood clotting §Primary constitutes for plasma membranes and internal cellular constitutes. §Activate vitamins that have a role in metabolic regulation 30 5/20/20 Proteins and Exercise Main job = anabolic processes § Due to the many structural roles of protein WE DON’T STORE PROTEIN § Protein breakdown (2-5% total energy requirements) § McArdle et al., 8th Ed Figure 1.24, p 37 Protein use After Exercise Minor role in energy synthesis during exercise § Post exercise, muscle protein synthesis increases substantially within 4 hours § Remains elevated for 24 hours post exercise § Two reasons for ingesting protein as an athlete: § Increased protein breakdown during long-term exercise § Increased protein synthesis during recovery § McArdle et al., 8th Ed Figure 1.23, p 37 31 5/20/20 Ingestion of Proteins §10-15% of daily calorie intake should be proteins § Important to ingest Protein daily because there are NO RESERVES of protein unlike CHO and FAT § Complete and incomplete proteins § Complete Proteins = eggs, milk, meat, fish and poultry McArdle et al., 8th Ed Figure 1.20, p 31 Recommended Protein Intake § Recommended dose 0.8g/kg body mass § Intense aerobic and resistance exercise may need to increase to 1.2-1.8 g/kg BM § No benefit has been reported from ingesting greater than 1.8 g/kg BM § Because athletes generally have a high caloric intake most would consume this in their normal diet http://cdn.media.cyclingnews.com/2015/07/14/2/sptdw224_670.jpg 32 5/20/20 Protein Intake § Eating 3x DOES NOT enhance work capacity, CHO does this § Muscle mass doesn’t increase from just eating high protein § Eat too much converted to glucose or FAT = Strain on the liver and kidney https://s-media-cache-ak0.pinimg.com/originals/ba/c6/78/bac6784483e74041809257fa9fb76329.jpg 33 5/20/20 Protein Step 1 = Hydrolysis https://bam.files.bbci.co.uk/bam/live/content/z7vjtfr/large 2 amino acids joined 2 singular amino acids with H2O added 34 5/20/20 St ep 2 - Tr ans am inat ion or Deam inat ion § Before an amino acid can be used for energy production it must go through a process of TRANSAMINATION or DEAMINATION § TRANSAMINATION is the removal of the amine group by transferring it to another substance § DEAMINATION is the removal of the amine group § NH3 is toxic in high concentrations and must be converted to UREA in the kidneys and excreted in urine § Occurs in the mitochondrial matrix of the liver and costs energy Catabolism of Proteins for Energy § Once the amino acids have had the nitrogen removed they can then join the energy pathways at various points: 1. Converted into pyruvate so that they can travel through the same pathways as glucose running through glycolysis (i.e. pyruvate to Krebs cycle/ETC or pyruvate to lactate 2. Converted to acetyl-CoA to enter the Krebs cycle 3. Converted into various intermediaries that are part of the Krebs cycle 4. Converted into gluconeogenic precursors to be converted to glucose in the liver § Difficult to calculate exact energy production from protein because it can pass through a variety of pathways 35 5/20/20 Ener gy Release f r om Pr ot eins – Sum m ar y § Proteins play a small part in energy production for exercise § Mostly contribute during endurance exercise, hard training periods and in periods when sufficient energy is not available from CHO and lipid sources § Proteins must first have their nitrogenous amine group removed via deamination or transamination and then they can be converted and used to contribute via pyruvate, acetyl-CoA, Krebs intermediaries and gluconeogenic processes § Ammonia is the by-product that must be converted to urea and removed in urine § Costs ATP and H2O The Metabolic Mill 36 5/20/20 The Metabolic Mill ¡ The metabolic mill depicts the interaction between the systems that we use to break down macronutrients and the energy that we produce out of these sources ¡ The Krebs cycle sits nicely in the middle as the joiner of our systems – fragments from CHO, fats and proteins can all feed through the Krebs cycle to produce energy ¡ Acetyl-CoA is often the important link between producing energy from all macronutrients McArdle et al., 8th Ed Figure 6.18, p 157 The Metabolic Mill - Summary § CHO § CHO enters glycolysis, converts to pyruvate § If intensity is low-moderate then pyruvate will convert to acetylCoA and enter Krebs cycle § Lipids § Fatty acids will be oxidised via β- oxidation, acetyl-CoA produced and will enter the Krebs cycle § Some of the glycerol will enter glycolysis, convert to pyruvate then acetyl-CoA and enter the Krebs cycle § Proteins § Some transamination or deaminated amino acids will enter glycolysis as pyruvate, be converted to acetyl-CoA and enter the Krebs cycle § Some will be converted to acetyl-CoA § Some will be converted to Krebs cycle intermediaries and enter the Krebs cycle directly 37 5/20/20 Excess fuel supplies § We store; § Glucose as glycogen § Proteins as part of our structure and as an amino acid pool § Lipids as triglycerides in adipocytes throughout the body § Any excess CHO, protein or lipids (that aren’t oxidised) will be put into storage as triglycerides § In this way, when we eat excess macronutrients, our energy systems become linked by having a common storage form https://www.google.com.au/search?hl=en&site=imghp&tbm=isch&source =hp&biw=1282&bih=851&q=sumo+wrestler&oq=sumo+wrestler&gs_l=im g.3..0l10.1333.4260.0.4511.13.9.0.4.4.0.395.935.22j1.3.0....0...1ac.1.64.img..7.6.703.MG7FMlEMm3I#imgrc=ft8H3FFsoy2K QM%3A Overview – 3 Energy Systems 38 5/20/20 Overview – the 3 energy systems Remember there are three bioenergetic metabolic pathways to produce ATP 1. ATP-PCr system § Cellular stores of ATP and phosphocreatine (PCr) – Anaerobic, rapid and limited supply 2. Glycolytic system § Anaerobic breakdown of CHO (glucose or glycogen), often to form lactate § Often called anaerobic glycolysis § Will supply energy rapidly for a short duration 3. Oxidative system § Aerobic breakdown of fuels (predominantly CHO and lipids) to form ATP § Also called the aerobic system/oxidative phosphorylation § Includes all processes running from glycolysis into the Krebs cycle and ETC as well as β- oxidation running into the Krebs cycle and ETC ATP-PCR System § Our most powerful energy source – will provide energy immediately § Simple anaerobic reaction and close to muscle fibres § Has capacity to provide energy for ~10 s, will typically be the predominant energy source for 5-7 s § Stores can be depleted and will be replenished during rest § Will take 3 -5 min to fully recover https://www.google.com.au/search?hl=en&site=imgh p&tbm=isch&source=hp&biw=1282&bih=851&q=wei ght+lifting&oq=weightlifiting&gs_l=img.1.1.0i10i24l9. 2357.4607.0.6511.14.11.0.0.0.0.528.2094.23j1j1j1.6.0....0...1ac.1.64.img..8.6.2084.lWJHeFepyS k#hl=en&tbm=isch&q=weight+lifting+australia+londo n&imgrc=CcYBlbusI9CRLM%3A 39 5/20/20 The Glycolytic System § Glucose and glycogen are the fuels for the glycolytic system CHO is the only macronutrient that can supply ATP anaerobically § Once exercise starts, intramuscular stores of glycogen are the primary source of fuel while blood glucose (from food ingestion or breakdown of liver glycogen) is transported into the cell § Liver glycogen will be hydrolysed (glycogenolysis) to mobilise glucose to enter the blood and the working muscles – finite source, so must be replenished by eating CHO regularly § Glucose and glycogen will be broken down anaerobically and rapidly in glycolysis to produce pyruvate and then lactate + H+ https://www.google.com.au/search?hl=en&site=imghp&tbm=isch&source=hp&bi w=1282&bih=851&q=400m&oq=400m&gs_l=img.3..0l10.1799.2523.0.2945.4.4.0 .0.0.0.250.488.22.2.0....0...1ac.1.64.img..2.2.485.7XI0FaXUrW8#imgrc=4usmveT2vAOdoM%3A The Glycolytic System § When the NAD+ carriers can’t cope with the production of H they will drop them off to pyruvate which will convert to lactic acid and then lactate and H+ § NAD+ carriers become overwhelmed when the ETC is not running fast enough to accept all of the H being produced § Causes the accumulation of H which lowers pH and causes fatigue https://www.google.com.au/search?hl=en&site=imghp&tbm=isch&source= hp&biw=1282&bih=851&q=athletic+fatigue&oq=athletic+fatigue&gs_l=img. 3..0i24.4229.10214.0.10444.20.19.0.0.0.0.364.2808.29j2.11.0....0...1ac.1.64.img..9.11.2796.GR4eeBKHunw#imgrc=sHsD6Pyr5 BeqLM%3A 40 5/20/20 The Glycolytic System § Will supply energy at a maximal rate ~5 s § Will last at this rate for several seconds § Will remain the predominant energy supply for 1-2 min (~75 s) https://www.google.com.au/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1282&bih=851&q=sprint+skating&oq=sprint+skating&gs_l=i mg.3...2225.4728.0.4907.14.10.0.2.0.0.549.1756.2-3j1j0j1.5.0....0...1ac.1.64.img..7.4.1202.fqDuZUVwJMY#imgrc=RWTvp-EvA0dJqM%3A The Oxidative System § Will process all macronutrients to supply ATP aerobically è will require O2….why? 1. CHO will pass through glycolysis onto pyruvate, acetylCoA è Krebs cycle è ETC 2. Lipids will pass through β- oxidation and will be converted to acetyl-CoA è Krebs cycle è ETC 3. Proteins will contribute energy through various pathways including glycolysis, pyruvate, acetyl-CoA and directly into the Krebs cycle and onto the ETC § O2 is required as the final acceptor of electrons in the ETC § Systems linked via acetyl-CoA and the Krebs cycle 41 5/20/20 The Oxidative System § Will supply most of the energy we use at rest and during low-moderate intensity activity § Will begin to supply energy as soon as exercise starts and will take over as the predominant energy system beyond 1-2 min (75 s) § Between lipids and relatively small supply of CHO (protein as a back up) could supply energy aerobically for many dozens of marathon runs § However the rate of supply is slow due to the extended processes involved, particularly in taking lipids from storage and converting them into ATP https://www.google.com.au/search?q=london+marathon&biw=1282&bih=851&source=lnms&tbm=isch&sa=X&sqi=2&ved=0ahUKEwjHh9HG9dXKAhVh3KYKHZQQAD0Q_AUIBygC#imgrc=h8Qn7gfI7WJLgM%3A Kenny et al. 5th Ed Table 1.1, p 40 Kenny et al. 5th Ed Table 3.3, p 65 42 5/20/20 I nt egr at iv e r es pons e of t he ener gy syst ems § All of our energy systems will supply some energy to almost any exercise effort § If we presume that all of our energy sources are fully stocked, the PREDOMINANT system will be decided by the intensity, duration and nature (intermittent vs. continuous) of the effort that we are completing § The function of the systems will overlap McArdle et al., 8th Ed Figure 11.2, p 229 I nt egr at iv e ener gy s y s t em r es pons e summary § During very short, high-intensity exercise efforts (510 s) the ATP+PCr system will predominate § During short, high-intensity exercise efforts (5-10 s up to 2 min) the glycolytic system will predominate § Any exercise effort over 2 min which is of a high intensity (e.g. marathon) = oxidative (glycogen) § Any exercise effort over 2 min which is of a low to moderate intensity = oxidative (lipids) https://www.google.com.au/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1282&bih=851&q=rowing&oq=rowing&gs_l=img.3...1161.1736.0.1853.6.5.0.0.0.0.0.0..0.0....0...1ac.1.64.img..6.0.0.FTGjxCgAgv0#imgrc=uhliNFgTuAc5OM%3A 43 5/20/20 100 m § 100 m running sprint § Less than 10 seconds § = ATP-PCr § Over 10 seconds § = Glycolytic § 100 m freestyle sprint § ~46 seconds § = Glycolytic 1000 - 1500 m § 1500 m Running § ~ 3:30:00 § = Oxidative § 1500 m Swimming § ~14 min § = Oxidative § 1 km Cycling § ~60 seconds § = Glycolytic § 1 km Canoe § ~ 4 min § = Oxidative 44 5/20/20 Muscle Fibre Types Fibre Type Characteristics Slow-twitch Fast-twitch (int) Fast-twitch Type I red Type IIa gray Type IIx white Slow oxidative (SO) Fast-oxidatve glycolytic (FOG) Fast-glycolytic (FG) Slow force Fast force Fast force Fatigue resistant Fatigue resistant Early fatigue 90 45 5/20/20 Type I fibres • Slow Twitch Fibres • Slow Oxidative (SO) • Appear red in whole muscle • ~50% of a “typical” muscle • Most frequently recruited fibres • High level of aerobic endurance • Relatively slow time to peak tension (110 ms) à Slow relaxation times • Relatively small in diameter Type I fibres • Most commonly recruited fibres in prolonged aerobic exercise due to: 1. High number of capillaries to supply O2 – helps to explain ‘red’ appearance 2. High number of mitochondria 3. High levels of myoglobin 4. High oxidative capacity 5. Greater number of aerobic enzymes 6. Greater triglyceride storage • Relatively low force production but high endurance capacity makes Type 1 Fibres highly fatigue resistant. e.g. postural muscles for sitting 46 5/20/20 Type II fibres • • • • • • • Fast Twitch Appear white in whole muscle ~50% of a ‘typical’ muscle – 25% type IIa and 25% type IIb High level of glycolytic capacity i.e. fast and powerful Type IIa fibres used more frequently than Type IIb fibres Relatively fast time to peak tension 50 ms à also fast relaxation times Relatively large in cross-sectional area Type II fibres 47 5/20/20 Type II fibres • Most commonly recruited fibres during exercise of a high-intensity, anaerobic sprint-type nature due to: 1. A faster form of myosin-ATPase • Faster energy supply and cross-bridge function 2. Highly developed sarcoplasmic reticulum • Faster Ca2+ release and reabsorption 3. Larger motor units – innervate >300 fibres 4. High concentrations of glycolytic enzymes 5. Increased storage of phosphocreatine and glycogen 6. High density of Ach receptors • These characteristics mean a high force production and very powerful contraction however Type II fibres fatigue more rapidly. Type II Fibre Sub-Groups Type IIa fibres • • Fast Oxidative Glycolytic (FOG) These fibres exhibit the following characteristics: – a fast shortening speed – moderately welldeveloped capacity for energy transfer from both aerobic and anaerobic sources • Aerobic - high level of succinate dehydrogenase (SDH) an aerobic enzyme • Anaerobic - high level of phosphofructokinase (PFK) an anaerobic enzyme – ~25% of a “typical” muscle 48 5/20/20 Type IIb fibres • ‘True’ Fast Glycolytic Fibres (FG) • These fibres exhibit the following characteristics: – Greatest anaerobic potential – Rapid shortening velocity • In some texts, FG fibres can be referred to as Type IIx Type IIx fibres • Fall midway between Type IIa and Type IIb Fibres in terms of their physiological and metabolic characteristics • ‘Intermediate’ Type II Fibre 49 5/20/20 Activity, Intensity and Fibre Type Activity Predominant Fibre Type Primary Fuel Used Low-intensity Type I Fat Carbohydrate Moderate-intensity Type I + Type IIa Fat Carbohydrate Prolonged exercise Type I + Type IIa Fat Carbohydrate High-intensity Type I + Type IIa + Type IIb PCr Carbohydrate Fibre Type Distribution • Non-athletes – Have approximately 50% slow and 50% fast fibers • Power athletes (i.e.Sprinters) – Higher percentage of fast fibers • Endurance athletes (i.e. Distance runners) – Higher percentage of slow fibers • Fiber type is not the only variable that determines success in an athletic event • Can fibre types/proportions change with exercise training? 100 50 5/20/20 Evidence for Fibre Distribution: Athletes • Endurance athletes – Higher percentage of Type I fibres in the major muscles used in their sport – ~ 90% type I Fibres observed in elite endurance runner’s gastrocnemius • Sprint/power athletes – Higher percentage of Type II fibres in the major muscles used in their sport • Middle distance athletes – Great range of both Type I and Type II fibres Great variation exists between successful athletes Muscle fibre type is only a minor factor potentially affecting athletic performance. Consider other factors such as cardiovascular fitness, muscle size, training status and motivation etc. Review Questions Q1. What are the by-products of triglyceride breakdown? (2 marks) Q2. Explain how the by-products of triglyceride breakdown can produce ATP. (3 marks) Q3. By what process is a protein broken down to its constituent amino acids? (1 mark) Q4. At what points (there are 3) can protein enter the metabolic mill and assist with ATP production? (3 marks) 51