Energy System Notes PDF

Metabolism Defined as all the chemical reactions where the body turns food into energy to sustain itself BMR ○ The rate at which the body uses energy when resting ○ The body is still pumping blood, repairing tissue, digesting food, regulating internal bod...

Metabolism Defined as all the chemical reactions where the body turns food into energy to sustain itself BMR ○ The rate at which the body uses energy when resting ○ The body is still pumping blood, repairing tissue, digesting food, regulating internal body temperature Factors affecting BMR: ○ Age, drops 2% every year after age 20 ○ Higher body fat % → lower BMR ○ Gender: Women have lower BMR ○ Diet: Eating less food means body will lower BMR to conserve energy ○ Stress: Stress increases symp. (fight or flight response) nervous system ○ Hormones - thyroxine and epinephrine increase BMR ○ Exercise = catabolism of fat even during rest, increasing BMR ○ Anabolism: building compounds Terms: ○ Anabolism - building compounds ○ Catabolism - breaking down compounds ○ ATP - immediate source of energy for bodily functions, like muscle contractions ○ PCr - Resynthesis ATP when it is in high demand, using a high-energy phosphate and ADP Catabolism  ○ Stage 1: Macronutrients (carbs, fats, protein) are broke down into their smaller units (carbs → simple sugars, fats → fatty acids, proteins → amino acids), then delivered through blood ○ Stage 2: These are broken down into CO2 and H2O in cells, energy (ATP) that was created by breaking down macronutrients is released to power the cells ATP (Adenine Base attached to ribose sugar) Phosphate, + ribose (sugar), adenine ○ Immediate source of energy, little stored in cells Provides energy for 2-6 sec ○ Continuously recycled, total in body = 3 ounces ○ Using up stored ATP → breakdown of stored nutrients for ATP resynthesis ○ 3 systems to recycle - type, length, intensity of activity determine  ATPase - enzyme that removes phosphate from ATP, turning it back into ADP - releases energy ( to do work) ○ ATP is less stable (repulsion of negatively charged phosphates against each other) Phosphorylation - phosphate removed by above process can be transferred to another molecule, the bond made absorbs/stores energy Oxidative Phosphorylation - Same as above, using oxygen to create a lot of ATP in the mitochondria (Synthesis of ATP from ADP) Functions ○ Growing, repairing body tissues ○ Muscle building, repairing contraction ○ Transport substances across cell membranes ○ Circulation, digestion, nerve transmission Bioenergetic conversion through cellular respiration ○ Proteins: Broken down into amino acids, some are converted to pyruvate THEN become acetyl coa, some directly become acetyl coa, and enter the krebs cycle. ○ Carbohydrates:  Plants and grains - broken down into simple sugars (4.1 calories of energy per gram) Converted from glucose (monosaccharide, product of complex carbs) into pyruvate through glycolysis Inside the mitochondria, pyruvate is turned into Acteyl Coa Carries acetyl to begin krebs cycle Excess glucose is stored as glycogen, depleted after few hours, synthesis ongoing as body processes carbs Then goes on to electron transport chain for oxidative phosphorylation Energy Systems Anaerobic: without oxygen ○ ATP-PC system: Anaerobic Alactic system, uses stored ATP and PCr, powering Type 2b fibres. ○ Located in cyto/sarcoplasm Lasts 0-15 seconds: quick and powerful exercises like sprinting, shot put, diving, etc. As PCr gets depleted during intense activity, ATP can no longer be synthesized  ○ Anaerobic Lactic, Glycolysis: Breaking down glucose, when ATP & PC have been depleted. Carbs are broken down (glucose, glycogen, etc.) to fuel ATP resynthesis. Type 2a or 2b fibres. Lasts 15 secs - 2 minutes (400m, basketball, start/stop) Located in cyto/sarcoplasm Lactic acid: byproduct that accumulates as muscle fatigues 2 ATP molecules per molecule of glucose Aerobic: with oxygen  ○ Cellular respiration: Carbs and lipids ar catabolised to CO2 and H2O with oxygen, releasing energy for ATP resynthesis (oxidative phosphorylation. Takes place in mitochondria, no lactic acid produced Most efficient source (95%) of ATP - yield 38 molecules of ATP per molecule of glucose Lasts 2 mins - few hours, type 1 fibres (cross country, biking, etc.) Used when glycogen is depleted → muscle fatigues, delayed by increase carb intake Fat Metabolism ○ 9 calories of energy per gram - good for prolonged exercise ○ Can be fatty acids, steroids, phospholipids, triglyceride stored, lipolysis into glycerol and three fatty acid chains) Converted to acteyl coa inside mitochondria → ATP production in krebs Protein Metabolism ○ 20 different amino acids, 4.3 calories per gram ○ Not stores, all fully functional in muscles ○ Amino acids are used to make glycogen, acetyl coa ○ Only used when other energy sources are depleted Cori Cycle and Lactic Acid  ○ Lactic acid during anaerobic activity → to liver Back to pyruvate → glucose, back into blood for future energy Takes place 30 mins after oxygen need for ATP production is met Why is sugar unhealthy? Sugar in glycolysis → pyruvate → Acetyl Coa, more sugar = more acetyl coa buildup → fatty acids → triglycerides Oxygen consumption during exercise: Body must quickly adapt to demand for ATP ○ Rate of production is determined on VO2 of the body 1-4 minutes for body to reach steady state oxygen consumption ○ Means that anaerobic systems always produce ATP at the start of exercise No one energy system: all work together and overlap to meet ATP demands Oxygen deficit Delay in oxygen uptake, temporary shortage at the start of exercise ○ Until steady state (plateau) is reached and gap is filled  Trained athletes reach steady state faster than untrained ○ Higher aerobic capacity → ATP production starts faster VO2 max the max. rate of a person’s oxygen uptake during exercise ○ Cardiorespiratory delivering oxygen to muscles ○ Muscle's aerobic ATP production capacity ○ Can be increased with exercise EPOC (excess post exercise oxygen consumption) When body uses/intakes more oxygen post-exercise than during rest ○ Restored ATP/PCr, oxygen (in muscle and blood) stores ○ Lactate → pyruvate ○ Elevated heart beat (recovery), breathing, hormones Lactate (Anaerobic) threshold Exercise intensity ↑, energy system goes from aerobic→anaerobic, increasing lactic acid levels in the blood (threshold) ○ 50-60% of VO2 max in untrained athletes ○ 65-85% of VO2 max in untrained athletes  The intensity at which lactate levels in the blood exponentially increase during exercise, due to: ○ Too much glycolysis too fast: pyruvate is produced but can’t enter mitochondria (krebs cycle) fast enough, converted to lactic acid ○ Type 2 fibres rely on enzymes that convert pyruvate to lactate ○ Lactate cannot be cleared quickly enough, more is produced than can be removed ○ Low muscle oxygen: Lactate buildup only occurs when the muscle use the anaerobic pathway glycolysis, producing more pyruvate → lactate Muscle Fatigue: Not solely because of lactic acid, correlation not causation ○ High Intensity Exercise (anaerobic): Lactic acid releases H+ ions, accumulation blocks Ca from binding with troponin, fewer strong binding sites (actin) are exposed As ATP is broken down, Pi is released, blocks myosin heads and impairing sliding filaments ○ Endurance training (aerobic) Less efficiency in releasing Ca into SR during ECC, due to less ATP available Fuel selection (Carbs are always the body’s preferred source) Influenced by three main factors Diet ○ High-fat, low carb diets → fats are energy source (weight loss) Exercise intensity (↑, energy source fats→carbs) ○ Low (70%) → Carbs ○ Crossover Point: when energy from carbs = energy from fat ○ Shift is caused by ↑ Type 2 muscle fibres High glycolic enzyme activity (↑ glycolysis) Less mitochondria and lipolytic enzymes (no break down fat) Epinephrine (adrenaline) speeds up glycolysis Exercise duration ○ ↑ duration = ↑epinephrine in blood = ↑ lipase activity = ↑lipolysis Inhibited by lactate/insulin High carbs = insulin released to reduce sugar (glucose uptake), reduces lipolysis Fat & Carb Metabolism Exercise 2+ hours = glycogen in muscle and livers depleted ○ Aerobic ATP needs pyruvate to be produced, glycogen→pyruvate in glycolysis ○ Less pyruvate = less Krebs cycle = less ATP produced ○ Fat metabolism = Krebs, “Fats burn in the flame of carbohydrates” Body Fuel Source Carb source: glycogen (muscle, liver), blood glucose Fat source: fatty acids (blood plasma), muscle triglycerides Protein source: Small amt. In skeletal muscle Lactate: skeletal, cardiac muscle