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McMaster University
Life Sciences
Danny M.Pincivero

Bioenergetics: What is metabolism?  Sum of all chemical reactions that occur in the body  Anabolic reactions: synthesis of molecules  Catabolic reactions: breakdown of molecules  Bioenergetics: converting food components (fats, proteins, carbohydrates) into energy The eukaryotic cell:  DNA is kept in a closed and distinct compartment [i.e. Nucleus]  Mitochondrion “energy factory”: o Where our cell makes energy (ATP)  Membrane: major source of cellular electricity AND intra-cellular signaling o Electricity a result of Na+ and K+ flowing across the membrane (the action potential) o Sensors detect what is going on outside the cell (i.e. insulin; signals the cell to do something from the outside of the cell)  Nucleus: home of cell’s genes o Making new protein; enables muscle cell to build new contractile proteins, enabling muscles to contract for a longer period of time o Increase production of protein for sake of harnessing macronutrients 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 ribosome by tRNA 5. In translation, mRNA is used to determine the arrangement of amino acids in the polypeptide chain Aspects of protein synthesis 1. Amino acids (dietary); the supplies for protein synthesis 2. Exercise (muscle contraction): stimulates the process; initiation of protein synthesis  Anabolic steroids; stimulate the process of protein synthesis faster Endergonic reactions:  Require energy to be added  Endothermic Exergonic reactions:  Release energy (transfer to mechanical and/or chemical AND thermal)  Exothermic Oxidation:  Removing an electron Reduction:  Addition of an electron  Oxidation and reduction are always coupled reactions  Often involves the transfer of hydrogen atoms rather than free electrons o Hydrogen atoms contains one electron o A molecule that loses a hydrogen also loses an electron and therefore is oxidized For something to be oxidized; something else needs to be reduced.  NAD plays an important role in glycolysis and inside the mitochondria; to make energy in the form of ATP What are enzymes?  Catalysts that regulate the speed of reactions o Lower the energy of activation  Factors that regulate enzyme activity o Temperature  There is an optimal temperature in which enzymes will work (not too hot or too cold)  Effects of exercise (increase temperature) o pH  There is an optimal pH level in Which the enzymes will work (not too acidic or basic)  Effects of exercise (more exercise causes the pH to become more acidic)  What role do enzymes play in metabolism? o Speeds up the breakdown of macronutrients that will eventually be involved in energy formation (ATP) Where do we get our energy from?  Energy “substrates” – carbohydrates, fats, and proteins  Where do these come from? o Diet o Storage: liver (glucose), muscle proteins  Why do we need their energy? o To form ATP; mechanical events 1. Muscle needs ATP for actin and myosin (proteins), to breakdown the protein you need ATPase (enzyme) 2. SERCA (sarco-endoplasmic reticulum, calcium, ATPase) 3. Na+/K+ ATPase (enzyme – pump) o Spending the ATP via ATPase (2 and 3 counts for most of our resting metabolism)  How do we get energy out of the substrates? o Depends on:  Substrate availability; providing the proteins, fats, and carbohydrates  Enzyme dynamics  Nervous system demand; high intensity (cross-fit) effects the NS  Metabolic “backup”; relates to rate at which we are tapping into a metabolic pathway Cellular energy  60-70% of chemical energy is converted to thermal energy o Why you feel hot when you exercise Energy for muscle activity  Bioenergetics: o Formation of ATP:  Phosphocreatine (PC) breakdown  Degradation of glucose  Oxidative formation of ATP o Anaerobic pathways:  Do NOT involve O2  PC breakdown and glycolysis o Aerobic pathways:  REQUIRE O2  Oxidative phosphorylation (glucose, fat, and protein) ATP PCr Glycolysis Oxidative phosphorylation THIS WILL PROBABLY BE THE GRAPH WE NEED TO DRAW Contribution to ATP (beginning of Oct 7 Lecture) % What is creatine?  Non-essential dietary element; found in meat and fish (usually raw) Time o Not readily available for consumption of food o Body makes it on its own  Greek derivative; keras, meaning flesh  Humans: made in two step process (liver and process)  Found mostly in skeletal muscle, the heart, spermatozoa, and retinal cells  Creatine biosynthesis steps: 1. Kidney: Argnine + glycine  guanidinoacetate + ornithine (not needed)  Arginine and glycine are conditionally essential (can be made provided another amino acid is present) 2. Liver: Guanidinoacetate + methionine  creatine + homocysteine (not needed)  Methionine is an essential amino acid found in many foods (meat, fish, eggs, cereal grains, sesame seeds)  Why is creatine important? o ATP re-synthesis for high intensity/velocity muscle contractions  Creatine phosphate (phosphocreatine, PCr, CrP) o Contains energy in phosphate bond o ATP  ADP + P + energy  ATP spending ATP is about getting P out of the bond, leaving you with ADP + P + energy  What happens when we run out of creatine phosphate? o Creatine kinase can run the reaction in both ways o When creatine phosphate runs out the reaction goes in the opposite direction Creatine phosphate usage during exercise  How fast you run out of creatine phosphate is dependent on your expenditure o 7 healthy men (sprinters, weight lifters) – near maximal recruitment of muscle fibers required (submaximal load)  Single leg knee extensions – MRI was tracking creatine phosphate concentration  At rest [PCr] = 100%  Cell has resting level of ATP stored for when activity begins; as soon as muscle is contracted it uses ATP (stored ATP can be used for appox 1-3 sec)  Cell does not waste anytime making ATP (hence drop in PCr concentration to 60%)  PCr concentration plateaus as other macronutrients begin to be used  PCr gives someone time to kick in glycolysis and possibly oxidative phosphorylation o Same 7 healthy men (using creatine monohydrate supplementation for 5-10 days)  Same experiment was carried out following supplementation periods  Creatine supplementation changed the creatine concentration in the muscle: o Resting and exercise PCr levels were increased  During exercise the PCr concentration remained higher than the control concentration o Exercise and recovery time constants  Took longer for PCr to reduce in concentration than in the control  Have more residual cretine after exercise and has more PCr
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