Chapter 2 Essentials of Bioenergetics and Anaerobic Metabolism PDF

Essentials of Bioenergetics and Anaerobic Metabolic Pathways ============================================================ Chapter 2 Learning Objectives =================== 1. Define the three major metabolic substrates and how they are metabolized to produce energy 2. Determine which metab...

Essentials of Bioenergetics and Anaerobic Metabolic Pathways ============================================================ Chapter 2 Learning Objectives =================== 1. Define the three major metabolic substrates and how they are metabolized to produce energy 2. Determine which metabolic substrates predominate during periods of rest and exercise of various types 3. Describe the production of energy from the adenosine triphosphate--phosphocreatine system and glycolysis 4. Describe the positive and negative features of the phosphagen and glycolytic pathways 5. Explain the adaptations of these energy systems that accompany training Metabolism: Applications ======================== - Why can a sprinter only sprint "all out" for a brief period? - How can a marathoner sustain a race pace for over 2 hours? - Where does this energy come from? - What factors limit performance and how can we overcome them? Why do we need energy? ====================== -Muscle contraction -Digestion -Reproduction Let's back up..... ================== Energy ====== - Our ability to do work - Work = capacity? - Examples? How do we get energy? =====================  [[https://www.iconfinder.com/]](https://www.iconfinder.com/) Through Metabolism ================== - Metabolism AKA bioenergetics - Food  energy - The sum total of all chemical reactions that go on in our cells. So where does the energy come from? ========================================================= - The sun - Humans and animals then consume plants and animals - The carbohydrates, protein, and fat in animals and plants is broken down to produce energy Energy Sources ============== - Chemical energy from food converted to mechanical energy - Resulting in muscle contraction and bodily movement - Three types of chemical energy that we consume through food are: -Carbs-\> broken into simple sugars (glucose, fructose, galactose) -Fat-\> broken down into triglycerides and fatty acids -Protien-\> to amino acids - Energy Sources ============== - Macronutrients are digested (broken down) into a usable form by the body - Carbohydrates:. broken into simple sugars (glucose, fructose, galactose) - Fats: broken down into triglycerides and fatty acids - Proteins: to amino acids - Then the usable forms are broken down to help form high-energy compounds (e.g., ATP) - We then break down ATP to release energy for muscle contraction  Adenosine Triphosphate (ATP) - The [energy currency], biologically useful form - Breaking of [phosphate bonds] releases energy for other biological work - When a [phosphate] is broken off it releases energy  ### What does a muscle need to contract and keep contracting? - Continual supply of ATP to match demand **Muscle activity slows down** **Less intensity -\> fatigue** **Limits performance** ### ATP - ATP "supply" = Muscle's ATP needs - Problem: ATP stored in limited amounts - Enough for [1-2s] of all out effort - Why? - So... What must happen to allow the working muscle to continue to contract? - ATP must be [replaced or resynthesized]. - How is this done? - Breakdown of [nutrients] through chemical reactions - Through [metabolism]. So, we need to break down food/nutrients to m ake ATP ===================================================== Fuels (substrates) for Exercise =============================== - A fuel (substrate) must: - Store chemical energy within chemical bonds - Substrates that we use Carbs (CHO) Fats Proteins Creatine phosphate (CPR,PC,CP) Carbohydrates ============= Carbohydrates - Rapid and readily available sources of energy - kcal/g - 3 forms: - Monosaccharides (single) - Disaccharides (two) - Polysaccharides (many) Carbohydrates ============= - Rapid and readily available sources of energy - kcal/g  - Blood sugar - Primary fuel for energy in the brain - Only monosaccharides used to make energy - Fruit sugar - Converted to glucose in the liver - Ex: fruit, honey, high fructose corn syrup Carbohydrates ============= - Monosaccharides form disaccharides Forming disaccharides by condensation ===================================== - Two sugars are joined by losing water (condensation) - Must be broken into monosaccharides for absorption from the GI tract into the blood  24 Polysaccharides =============== - Many monosaccharides bonded together - Starch, glycogen, and fibre - Cellulose is a form of insoluble fibre - Only starch and glycogen are digestible - Glycogen: storage form of glucose in mammals - Stored in liver and muscles (muscle glycogen) 25 The Science of Nutrition, Canadian Edition. Thompson et al., Glycogenesis ============ - Genesis = make or form - Formation of [glycogen] from [glucose].  Glycogenolysis ============== - Lysis = break apart - Breaking down of [glycogen] into [glucose].  Glycogen storage ================ When blood glucose drops, fatigue occurs Muscle Liver  Both glucose and glycogen are important substrates during rest and exercise =========================================================================== Carbohydrates for Energy - Very important fuel - [During exercise.] - for the brain CNS (brain). Why? - Pro - ATP can be produced [quickly, rapidly] & readily available - Con - Can be depleted after about 2 hr of prolonged exercise - Influenced by carbohydrate content of diet Fats ==== - Can be metabolized for energy - Triglycerides: Storage form of fat - 1 glycerol - 3 fatty acids (4-24 carbon atoms)  Lipolysis ========= - Lipo: lipid - Lysis: Break down - Fatty acids are liberated and used to make energy Fats for Exercise ================= - Important energy reserve - Protection/insulation - Transport/storage of [fat ssoluble] vitamins - Con - Produce ATP [slowly]. - At rest, provides \>½ the ATP - But little during [intense] exercise - Pro - Fat stores "not" depletable Proteins ======== - Small amount used for energy - Made from [amino acids] linked together - How are proteins different to carbohydrates and fats?  The Building Blocks of Proteins =============================== - Combination of different amino acids make proteins the essential amino acids have to be consumed while the other 11 don't. non essential amino acids can be produced in the body. Enzymes ======= - Facilitate a chemical reaction - Speeds it up - Unique shape - Ends in *ase* - Protease - Lipase  Energy Systems or Pathways: The Basics ====================================== - A series of chemical reactions that transforms substrate(s) to product(s). - Anabolism - The process of [making new] molecules from smaller ones - Catabolism - The [breaking down] of larger molecules into smaller molecules Anabolism ========= - Critical for growth and repair - Require energy - Catabolism ========== - Begins with digestion - Substrates are further broken down and release energy - This is used to synthesize ATP - ATP Is then broken down for muscle contraction In metabolism triglycerides are broken down to make atp Condensation and Hydrolysis ===========================   We only have enough stored ATP for 1-2 s of activity ==================================================== How do we do get ATP? -metabolism Energy Systems/Pathways ======================= 1. [ATP-PC®]. 2. [ Anaerobic] metabolism (glycolysis) 3. [ Aerobic] metabolism (cellular respiration) How the Energy Systems Differ ============================= - Substrates used - Glucose, glycogen, fat protein, phosphocreatine - Speed of ATP production - \< reactions = quicker - Capacity for ATP production - How much/ total energy production - "Size of the tank" - Metabolism byproducts - Creatine, lactate, CO~2~, etc., - Oxygen requirement **Anaerobic Glycolysis** **Aerobic metabolism** -- -- -------------------------- ---------------------------------------------- Muscle glycogen Glucose/glycogen, fatty acids, & amino acids Moderate Lower Small Large No Yes Energy for High-Intensity Efforts: ATP-PC system ----------------------------------------------------------------------- - Phosphocreatine (PCr or PC) system - PC is composed of - PC stored in sarcoplasm of muscle - Small \# steps to produce ATP Given that there are a small number of steps in the ATP- PC system and that PC is found in the muscle, how do you think this affects the rate of ATP formation? =============================================================================================================================================================== Energy for High-Intensity Efforts: ATP-PC system ------------------------------------------------ - Energy source for activities requiring **quick energy (high intensity)** - **Duration:** Brief - [Dominate]s for 3-15 second all out effort - Examples? - **Rate** of ATP production is important ATP-PC: Mechanism ================= - Energy released from breakdown of phosphocreatine is used to produce ATP - PCr  Cr + P + energy - ADP + P + energy  ATP - This ATP is then broken down and the energy liberated is used for muscle contraction - ATP  ADP + P + **[energy]** +H - Which enzyme is important in this reaction? - How does PCr breakdown lead to ATP formation? - ↑ in enzymes or substrates can increase ATP production Intramuscular ATP and PC Levels: During High-Intensity Exercise --------------------------------------------------------------- 56 What's causing fatigue? ======================= - Recall that - ATP  ADP + P + **[energy]** +H - Accumulation of [H+] increases acidity, causing fatigue - [H+] needed for ATP formation but - If ATP breakdown exceeds production, then [H+] accumulates - Increasing acidity and causing fatigue Replenishing PC Stores ====================== - Happens during recovery only - Why? - Once depleted we have to use the other energy systems to generate ATP - Anaerobic metabolism (glycolysis) - Aerobic metabolism (cellular respiration) Why can a sprinter only sprint "all out" for a brief period of time? ==================================================================== -PC reducing ============ - accumulation of hydrogen due to ATP being broken down ======================================================= -Fatigue ======== -Not making enough ATP ====================== ATP-PC: Adaptations to exercise ------------------------------- - Mixed results about changes in creatine kinase activity following training - ATP & PC may increase with specific types of training. - Results are mixed but.... - Endurance training has no effect. - Elevations in content of intramuscular ATP & PC may not be necessary to enhance short-term, high-intensity performance It can improve performance Ergogenic effects ================= - Short-term benefits following 5-7 day loading include increased - Power production - Sprint performance - Work performed (i.e. multiple sets of maximal effort) - Chronic training with elevated creatine levels - Increases lean mass gains - Improves strength - Improves power Creatine: Mechanism of action ============================= - ↑ muscle PCr Creatine Kinase Energy for longer high-intensity efforts ======================================== - If exercise goes beyond ATP-PC system capacity then other systems are involved -- ↑ contribution from glycolysis McArdle, Katch and Katch.. Exercise Glycolysis ========== - The breakdown of [glucose/glycogen to pyruvate]. - "Glucose splitting" - Occurs where??? - 10 step, anaerobic reaction - Does not require [oxygen]. Glycolysis ========== **Glycolysis** - The breakdown of glucose/glycogen to pyruvate 2x3 carbon mlc-\> In the Absence of Oxygen ======================== **Glycolysis** - In absence of oxygen - Pyruvate is converted to [lactate]. When Oxygen is Available ======================== **Glycolysis** - In the presence of oxygen - Pyruvate is converted to acetyl CoA - Used for aerobic metabolism Glycolysis overview =================== - Anaerobic (fast): not using oxygen oxygen - Aerobic (slower): using oxygen Glycolysis (Glucose into Pyruvate) ================================== - This process can occur: - **[Fast (anaerobic)]**- when the cells need lots of energy quickly - **[Slow (aerobic)]**- when the cells need less energy, usually over a longer time frame Glycolysis: Substrate ===================== - Glucose (blood) or glycogen (muscle) - Glycogenolysis - Glycogen breakdown Glycolysis: Substrate ===================== - Glycogen phosphorylase -- Cleaves off a  Glucose: Substrate ================== - Hexokinase - Catalyzes glucose to glucose 6- P Glycolysis: Substrate ===================== - Glucose to glucose 6 phosphate - Uses ATP - Glycogen to glucose 6 phosphate - Does not use ATP Glycogen Phosphorylase  **Glucose** -------------- ------------- --- ATP used 2 1 ATP produced 4 4 Net ATP 2 3 - Two H+ are removed - Combined with NAD+ - Two NADH are produced - Also contains 2 e- - NADH is important for aerobic metabolism - Why? -Provides hydrogen and electrons to generate lots of ATP in the mitochondria  - Two pyruvate molecules -- ----- 2/3 2 2 -- ----- Glycolysis overview =================== - In the absence of oxygen pyruvate is converted to [lactate]. - 2 H+ are donated from NADH to pyruvate to form lactate - [Lactate dehydrogenase]. - This process can occur: - **[Fast (anaerobic)]**- Reminder ======== **Glycolysis** - **[Slow (aerobic)]**- when the cells need less energy, usually over a longer time frame Why Lactate is Important ======================== - We need NAD+ for glycolysis to continue - 2 options - Mitochondria requires oxygen - NADH donates h+ to pyruvate to make lactic acid 84 Lactate Response to Exercise ============================  - Describe what happens to lactate over the course of exercise. First graph- during submaximal exercise lactatate increases, then plataues Second -- the submaximal exercise increases the lactate There is a lag because lactate is produced in the muscle and it has to get into the blood. - Describe what you see - Based on what you know about energy systems does this make sense? Explain. The longer the distance, the less lactate Lactic Acid and Fatigue ======================= - Lactic acid quickly dissociated into lactate and hydrogen ions - Hydrogen ions increase [acidity] result in fatigue Hydrogen is accumulated Causing an increase in PH Anaerobic Glycolysis and Fatigue ================================ - Pain & burning in the working muscles - Due to h+ build-up (the h+ comes from lactic acid) - Heavy breathing & breathlessness - Due to oxygen debt from aerobic metabolism Anaerobic Glycolysis and Recovery ================================= - Reduction in pain, exertion possible again: 2 -- 3 minutes - Largely depends on the extent of lactic acid accumulation - Full recovery in [30 min] or greater. Is there anything we can do to combat acidosis? =============================================== - Rapid ATP production - Limited capacity - Because of acidity - Dominant energy system from [20-30s] up to approx. [2-3 min] (for all out exercise) Common Adaptations ================== - Improved enzyme function (enzyme activity) Wikipedia commons Glycolysis: Enzyme Adaptations ============================== - Changes in glycolytic enzymes may improve performance - ↑ ATP availability from glycolysis - Key studied enzymes: - Glycogen phosphorylase (intramuscular glycogen to glucose-6-p) - Phosphofructokinase (rate limiter) - Lactate dehydrogenase (pyruvate to lactate) Glycolysis: Enzyme Adaptations ============================== - Enzymes ↑ due to sprint training and sometimes weight, & endurance training\* - Glycogen phosphorylase (glycogen to glucose-6-p) - Phosphofructokinase (rate limiter) - Endurance training \ takes longer to run out - Weight and sprint training show mixed results Glycolysis: Buffering Adaptations ================================= - Endurance & sprint training ↑ buffering capabilities - Buffering H+ ↑ performance & recovery in activities that have high muscle acidity - Allows for more ATP generation before fatigue Interactions of Aerobic and Anaerobic Metabolism ================================================ - Anaerobic: Most ATP for high intensity short duration, maximal physical activity - Aerobic: Most ATP for long duration low intensity  A 3-Second Sprint ================= - It's not always 1 or the other, it's one tends to dominate - 3-second sprint: - 87% ATP-PC, 10% glycolysis, 3% aerobic - 6-second sprint: - 50% ATP-PC, 44% glycolysis, 6% aerobic - 30-second sprint: - 17% ATP-PC, 45% glycolysis, 38% aerobic Thanks ====== 101