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September 30-Oct 21; Bioenergetics - Lecture Notes - LIFESCI 2N03

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Life Sciences
Danny M.Pincivero

LECTURE 4 LIFESCI 2N03 Lecture 4: Bioenergetics September 30, 2013 Metabolism  Sum of all chemical reactions that occur in the body  Anabolic reactions – synthesis of molecules  Catabolic reactions – breakdown of molecules  Bioenergetics – converting foodstuffs (fats, proteins, carbohydrates) into energy Eukaryotic Cells  DNA is kept in a close and distinct compartment  Mitochondrion – energy factory; where the cell makes the money “money” allowing the cell to do certain things  Cellular Membrane – major source of cellular electricity (Na+ and K+ flowing across membrane creating an action potential) and intra-cellular signaling; selectively keeps cell in/out of cell; o Eg/ insulin will signal increase in cellular uptake of glucose; has to signal to cells on receptors on cell membrane  Nucleus – home of cells genes; making new proteins for muscle cells to enable it to produce more force Protein Synthesis 1. DNA contains information to produce proteins 2. Transcription produces mRNA 3. mRNA leaves nucleus and binds to ribosome 4. Amino acids are carried to the ribosomes by tRNA 5. In translation, mRNA is used to determine the arrangement of amino acids in the polypeptide chain o Amino acids (dietary)  supplies; increase enzymes to increase cell capability of breaking down sugar or fat as a substrate of energy; amino acids are the building blocks of enzymes (proteins) o Process  Exercise (muscle contract) begins process  Dietary amino acids – ingestion of amino acids may be sufficient to begin synthesis of proteins  Anabolic steroids – synthetic drugs that stimulate process faster (go directly to DNA, increases rate of synthesis; not allowed in athletics)  Endergonic reactions – require energy; endothermic  Exergonic reactions – release energy (transfer to mechanical and/or chemical and thermal); exothermic  Oxidation and reduction are coupled reactions o Oxidation – removing an electron o Reduction – addition of an election o Often involve transfer of H atom rather than free election  H atom contains one electron  A molecule that loses H also loses an electron; therefore is oxidized o NAD – oxidizing agent; electron carrier; can readily bind electrons; becomes reduced o NADH – reducing agent; loses an electron; becomes oxidized 1 LECTURE 4 LIFESCI 2N03 Enzymes  Enzymes – catalysts that regulate the speed of reactions; lower the activation energy  Factors that regulate regular enzyme activity o Temperature o pH  Figure: Sucrase binds disaccharide substrate (sucrose) and initiates chemical reaction to break bond – results in two monosaccharide (glucose and fructose); sucrose remains the same, can go on to next disaccharide  Role in Metabolism – speeds up the breakdown of macronutrients that will eventually make us “money” (ATP, energy)  Effect of Temperature – increase temperature = danger of denaturing enzymes o Exercise requires temperature regulation, or else extensive damage can occur to structural proteins and enzymes  Effect of pH – increase acidity (lower pH) = enzyme activity decreases Energy  Energy “substrates” – carbohydrates, fats and proteins o Come from diet and storage (liver, glucose; muscle protein) o Energy needed to form ATP  Muscle cell 1. Myosin ATPase – contractile muscle and enzyme; can bind ATP and harness energy; responsible for force production 2. SERCA – sarco endoplasmic reticulum calcium ATPase; put calcium back after muscle contraction, or keep muscle rested 3. Na+/K+ ATPase – keeps muscles from contracting uncontrollably  ATPase – enzyme that can bind to ATP; expend energy  SERCA and Na+/K+ ATPase are responsible for most metabolism during rest  Getting energy from substrates depends on o Substrate availability – diet is a factor o Enzyme dynamics – pH and temperature; exercise; eg/ if you do endurance training, you become better at endurance activities o Nervous system demand – activate nervous system to activate muscle tissue 2 LECTURE 4 LIFESCI 2N03 o Metabolic “backup” – maximize usage of glucose, then body shifts to other energy substrate  Cellular Energy o Mechanical events when phosphate is removed – harnesses chemical energy to convert to mechanical energy and thermal energy (60-70%)  Energy for Muscle Activity o Formation of ATP  Phosphocreatine (PCr) breakdown  Degradation of glucose  Oxidative formation of ATP o Anaerobic pathways  Do not involve O2  PC breakdown and glycolysis (breakdown of glucose)  Rapid  Enzymes in cytoplasm o Aerobic pathways  Require O 2  Oxidative phosphorylation (glucose, fat and protein)  Enzymes in mitochondria ATP PCr Glycolysis Oxidative phosphorylati2n, O Use glucose and fat, protein is last resort ` % contribution to ATP  3-5 sec 8-12 sec Exercise Time Creatine  Non-essential dietary element; found in meat and fish o Cooking meat destroys creatine – don’t need to ingest because our body makes it (non-essential)  Greek derivative; kreas = flesh  Found primarily in skeletal muscle, heart, spermatozoa, retinal cells 3 LECTURE 4 LIFESCI 2N03  Made in 2 step process (liver and kidney) in humans 1) Kidney – Arginine + Glycine Ornithine Arginine + Glycine Guanidinoacetate  Conditionally essential  Arginine – made form citrulline  Glycine- made from serine  These amino acids must be present in order for body to make it 2) Liver – Guanidinoacetate + Methionine Homocysteine Guanidinoacetate + methionine Creatine  Essential amino acid methionine  Eggs, meat, fish, sesame seeds, cereal grains  Importance – ATP re-synthesis for high intensity/velocity muscle contraction; o Creatine phosphate (phosphocreatine, PCr, CrP) – contains energy in phosphate bond o ATP is only useful if you expend it – energy from phosphate bond; results in ADP + phosphate group + energy o Pathway – creatine phosphate for energy; creating ATP PCr + ADP ATP + Cr (two way reaction; creatine kinase is the enzyme) o Run out of creatine phosphate – reaction reverses only if the need for energy decreases (during rest) Cr + ATP PCr + ADP  Creatine Kinase – 381 amino acid sequence o Functional protein  Breakdown glucose – 15 chemical reactions to make 2 ATP  Creatine to make ATP is much more rapid; quickly results in decreased PCr  Creatine Phosphate used during exercise o Eg/ Knee exterior muscle cell  To move in direction quickly; action reaction – ground reaction force = force football player exerts on ground  has to generate knee extensor torque, driven by muscular action  Sarcomere – forces generated at the sarcomere (muscle); muscle contractile protein; when they contract, relax and interact movement and force is generated  Thin and thick filaments contract and relax  High metabolic demand; only contract when ATP is expended  Myosin ATPase (red line) takes ATP, catalyze reaction, get energy and produce mechanical energy (and heat)  PCr in muscle cells – PCr + ADP --creatine kinase--> ATP + Cr  Advantage – 1 chemical reaction to get ATP vs. glycolysis 15 chemical reactions (2 net ATP for 1 glucose molecule)  quickly make ATP  Run out of PCr quickly  Note – use of supplements for more PCr o Eg/ Muscle [phosphocreatine] dynamics following the onset of exercise in humans; the influence of baseline work-rate; Andrew M. Jones, Daryl, P. Wilkerson and Jonathan Fulford  Subjects – 7 healthy men (sprinters, weight lifters; activities that require near maximal recruitment of muscle fibers for high intensity exercise)  Exercise – single leg knee extension 4 LECTURE 4 LIFESCI 2N03  Moderate – 40% highest work rate (6 min)  Heavy – 80% highest work rate (6 min)  Dotted vertical line = onset of exercise (0 second)  Resting level of ATP to be used at onset of exercise; begin PCr pathway to create ATP (as seen at 0 seconds)  6 minutes – submaximal  Burn PCr to get exercise started, it reaches 60% of resting value (starting value 100%) – start using other macronutrients (glycolysis breakdown of glucose and oxidative phosphorylation through fat breakdown occurs)  PCr allows us to get started Heavy exercise condition o Creatine phosphate supplementation – increase the muscle stores of Creatine phosphate; extends high intensity exercise and speeds muscle recovery o Can get creatine from high raw meat diet o Supplement Form  Types  Creatine monohydrate (most population)  Creatine anhydrous (CON-RET)  Creatine phosphate  Creation-O-phosphate  Creatine Supplement Forms  Creatine monohydrate – holds one molecule of water  Creatine Anhydrous – drying of creatine monohydrate (at 100˚ C); more concentrated form of creatine o More expensive o In reality, having a higher concentration is probably not that much different  Creatine salts – created by combining creatine and a strong acid (pyruvic acid, malic acid, citric acid)  Creatine Content  Creatine anhydrous 100%  Creatine monohydrates 88%  Creatine malate 75%  Creatine citrate 66%  Creatine solubility in water – greater solubility with creatine salts than creatine monohydrate  Creatine stability  Creatine monohydrate most stable (i.e. long time to degrade; therefore long shelf life; years)  Creatine degrades in warm, acidic water – should be consumed immediately after dissolving in water o Bioavailability – ability for body to absorb a nutrient 1) Absorb creatine from small intestine into blood 2) Uptake creatine into muscle tissue o Creatine solubility in water  Greater solubility with creatine salts than creatine monohydrate  Dietary creatine (supplement form) intestinal absorption close to 100%  Muscle tissue uptake stimulated by insulin  Insulin – pancreatic hormone; maximize insulin secretion with intake of high glycemic index food (high sugar in food) 5 LECTURE 4 LIFESCI 2N03 o Analysis of the efficacy, safety and regulatory status of novel forms of creatine; Toshitada Inoue, Richard B. Kreider  Retained creatine after 3 days of supplementation  Creatine monohydrate dissolved in water – result in bioavailability; body absorbs it, muscle takes it up,  Creatine monohydrate dissolved in glucose solution – greater retention of creatine monohydrate in the body; provides muscle cells with extra fuel o Creatine Dosage  Loading Phase – 1 4-6 days – 20 g/day (4, 5 gram services)  Bombard muscle tissue with creatine and taking up of creatine; body will filter out excess  Maintenance Phase – 5 g/day afterwards  Takes 2-3 days for tissue creatine accumulation o Creatine and Exercise Performance – 5-20% improvement in short-term exercise (cycling, sprinting, jumping resistance exercise o Side Effects  Increased weight gain (water retention in muscle)  Nausea, vomiting, diarrhea; may occur with exercise; from ingesting synthesized substance  Increased urinary creatine and creatinine – may be related to kidney inflammation  Excess creatine excreted  Creatinine – byproduct of creatine  Kidney inflammation – excess creatine in cardiovascular system; kidney has to filter it out; few cases  Altered fluid balance; may predispose to dehydration  Occur during first few days; body is not use to excess creatine; water retention – may throw off fluid balance  Some bloat, others have no side effects  Anhydrous does not result in water retention  Negative feedback from exogenous supply; decreases natural production  Creatine Phosphate – Recovery Following Exercise o Influence of dietary creatine supplementation on muscle phosphocreatine kinetics during knee-extensor exercise in humans; Andrew M. Jones, Daryl P. Wilkerson, Jonathan Fulford  Measure creatine in muscle  Subjects – 7 healthy men (sprinters, weight lifters)  Exercise – single leg knee extension  Moderate – 40% highest work rate (6 min)  Heavy – 80% highest work rate (6 min)  Creatine monohydride supplementations 
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