Exercise Metabolism Flashcards
Adenosine Triphosphate (ATP)
The main form of energy in the human body.
Made of:
Adenine (a nitrogenous base)
Ribose (a sugar molecule)
Phosphate groups (3 linked w/ High Energy bonds)
Bioenergetics
The study of biochemical reactions that manage energy in the body.
Metabolism
All chemical reactions that occur in the body to maintain itself.
Exercise Metabolism
The relationship of bioenergetics to physiological changes and demands from exercise.
Energy Metabolism: flowchart
Intake: Chemical energy in the form of macronutrients, Carbs and Fats.
Conversion: Carbs & Fats into ATP
Metabolic process to use energy
Express: Chemical waste in the form of Co2, water & heat.
First law of thermodynamics
Energy cannot be created or destroyed, only recycled or converted from one form to another, known as ENERGY BALANCE.
This is the reason why energy taken into the body is stored as excess mass when it is not used to perform activity.
Substrates
Intermediate forms of nutrients used in metabolism to create ATP.
Protein’s amino acid chains
Carbs
Fats
The label “essential nutrient”
Substrates that cannot be created internally and must be consumed in the diet.
Glucose vs. Glycogen
The simplest form of Carb used by the body to make energy.
Derived from Carbs, but can also be made internally via gluconeogenisis by breaking down protein’s amino acids, or Fats.
Glucose is used to make ATP or stored in liver & muscle cells as Glycogen for later use.
Glucose is used for brain function & high energy exercise, but Fats primarily fuel the body at rest.
Glucose vs Fat for energy production
Glucose is used when the body needs a quick way to produce energy. It can be used faster than Fat because it can be metabolized anaerobically.
Fat must be converted to ATP in the presence of Oxygen.
Ventilatory Threshold 1 (vt1)
The point of exercise intensity where the body is using a 50:50% mix of Carbs & Fats to fuel the body.
The crossing from Light to Moderate level exercise.
Breathing becomes significant but can still speak in sentences.
Ventilatory Threshold 2 (vt2)
The point at which exercise intensity is so high, that only glucose can meet the body’s energy demands.
Glycolysis produces more co2 than fat oxidation, so not only does inhaling increase, but the need to rapidly exhale co2 also increases, making talking very hard.
Fat & Triglycerides
A macronutrient that is an important energy source during rest & sub-v1 exercise.
Its substrate form is Triglyceride, which is known as Free Fatty Acid when it is in the bloodstream.
Triglycerides are consumed in the diet & are made by the liver.
High Carb intake causes the liver to convert excess calories into Triglycerides.
They are stored in fat cells until needed. Then they are released as Free Fatty Acids for energy production.
Protein
Macronutrient made up of long chains of amino acids linked by peptide bonds that are the building blocks of body tissue.
20 amino acids are used by the body & 9 are essential
Essential vs. Non-essential Aminos
Essentials must be consumed in the diet, since they can’t be synthesized in the body. There are 9:
Non-essentials can be synthesized in the body from consumed Carbs & Fats.
Negative Energy Balance
Insufficient Carb or Fat substrates availability leads to the recruitment of Protein’s amino acids for energy production.
These aminos are derived from newly consumed Protein or the breakdown of muscle tissues.
Uses processes of gluconeogenesis or ketogenesis.
Ketogenesis
The formation of Ketone bodies (3 molecules: acetone, acetoacetic acid & beta-hydroxybutyric acid Bhb) produced by the liver from NON-FAT sources, like Protein’s amino acids or by-products of fatty acid breakdown.
Used for quick fuel, as the can be ANAEROBICALLY metabolized similar to glucose.
Ketosis
When the body runs low on glucose or glycogen stores, the liver produces Ketone bodies (3 molecules of acetone, acetoacetic acid & beta-hydroxybutyric acid Bhb)
The Ketone bodies cannot be stored & must be used immediately. Together w/ gluconeogenic glucose, they resolve glucose/glycogen deficiency.
The 3 Ketone Bodies
Acetone
Acetoacetic Acid
Beta-hydroxybutyric Acid, (Bhb)
Conditions for Ketosis
Very low overall calorie consumption
Low-carb, or Ketogenic Diets
Consuming Exogenous Ketones
Lack of insulin or insulin resistance
Nutritional Ketosis vs Ketoacidosis
Dietary and supplementary means to increase ketone levels between 0.5-1.5 mmol/L
Levels of Ketones, which are acidic, are too high, causing metabolic acidosis, as seen in type 1 diabetes or severe insulin resistance.
ADP
Adenosine diphosphate
When ATP is used for mechanical work, one of the 3 HIGH ENERGY phosphate bonds is broken, resulting in ADP & a free phosphate group.
Will convert back to ATP when enough food derived or bodily stored substrates become available.
High-energy bonds
Bonds that store chemical energy, and release it when broken (ie-ATP’s phosphate bonds).
Phosphorylation & the 3 Metabolic Pathways
The body’s way of generating ATP from ADP via the ATP-PC system.
The 3 Metabolic Pathways:
ATP-PC System: Immediate energy for only 15-20s
Glycolytic System (glycolysis): Short-term energy for about 2 mins.
Oxidative System: Long term energy, relying on oxygen
*All 3 work systems work together to fulfill the body’s energy needs, and the intensity of an activity will dictate which system is primarily used. None ever stop and are constantly recharging.
Exercise intensity as it relates to the metabolic pathways
At rest & low intensity, Free Fatty Acids provide most of the energy via the Oxidative System.
When intensity ramps up, for the first 10-15 seconds, as the body transitions from low to high intensity, the ATP-PC provides the most energy.
As the ATP-PC exhausts, glycolysis via the Glycolytic System, is already charging up to sustain energy for about 2 mins.
All while the Oxidative System is preparing to take over for the long term.
*The better a person’s cardio, the more efficiently the Oxidative System can support high intensity w/o having to rely as heavily on anaerobic processes.
ATP-PC System
One of the 3 Metabolic Pathways used to provide energy.
Also known as the phosphagen or phosphocreatine system.
Occurs in the muscle cells.
It is the simplest & fastest way of generating ATP by anaerobically taking a phosphate from a phosphocreatine molecule and adding it to leftover ADP from previous mechanical work.
The ATP-PC System is activated at the outset of any increase in activity intensity & will provide energy for 10-15s.
Glycolytic System
One of the 3 Metabolic Pathways used to provide energy.
Uses glycolysis, which is the chemical breakdown of glucose occurring in the cellular cytoplasm, turning it into ATP & pyruvate.
*Can be anaerobic, but the fate of the pyruvate produced depends on whether oxygen is available. If o2, then enters the Oxidative System (where it is turned into Acetyl-CoA) & then Citric Acid Cycle for further energy production. If no o2, then it becomes lactate.
It is slower than the ATP-CP system, but can provide energy for 30-60s plus.
Lactic Acid
The Glycolytic System produces ATP & pyruvate from glycolysis.
When no oxygen is available, pyruvate turns into lactate, releasing a free hydrogen ion in the process.
The hydrogen ions lower muscle pH, causing acidosis & resulting pain/fatigue and impaired muscle contractions.
Because of this, the combination of lactate PLUS hydrogen ions are called lactic acid.
**But lactate is not a waste product, because it is processed by the liver in a separate metabolic process know as the Cori Cycle, where ATP is used to convert lactate back to pyruvate and subsequently glucose.
Cori Cycle
Metabolic process in the liver of recycling lactate back into pyruvate, and ultimately into glucose.
Oxidative System
One of the 3 metabolic processes for providing energy.
The most complex and slowest. It uses oxygen to convert macronutrient substrates into ATP, known as oxidative phosphorylation.
Long term aerobic energy.
Oxidative System: flowchart
Macro: Fat
Substrate: Free Fatty Acids
Chemical breakdown: Beta-oxidation
Product: Acetyl-CoA
Macro: Carb
Substrate: Glucose
Chemical breakdown: Glycolysis
Sub-Product: ATP & Pyruvate
Converted into Product: (when pyruvate is w/ o2) Acetyl-CoA
Macro: Protein
Substrate: Amino Acids
Chemical breakdown: Deanimation
Product: Acetyl-CoA
All substrates are broken down to Acetyl-CoA.
Chemical reactions of the Citric Acid Cycle (Krebs) & Electron-Transport Chain take place in the mitochondria (matrix and inner mitochondrial membrane).
CAC produces a few ATP & co2 (1ATP per cycle) It most importantly removes high energy electrons & provides them to the ETC to use for energy production.
ETC is the where free o2 unites w/ electrons and produces more ATP and water.
Electron Transport Chain
Where oxidative phosphorylation takes place.
Located in the inner mitochondrial membrane, it is a series of protein complexes that create a gradient of stored hydrogen ions that allow electrons provided by the CAC to move through the gradients.
When ATP levels fall & ADP levels rise, the hydrogen gradient is harvested by a protein ATP Synthase to turn ADP into ATP and water.
Acetyl-CoA
The precursor for macronutrient substrates to enter the CAC.
Beta-oxidation
The breakdown fats (FFA) into Acetyl-CoA for use in the CAC to produce ATP.
Mitochondria and relationship to beta-oxidation
The rate at which a person can breakdown fat depends on the number of mitochondria in the muscle cell AND the amount of o2 delivered by the blood.
Well conditioned people have more mitochondria in their muscle cells, and can therefore break down more fat.
One fatty acid molecule vs glucose in ATP production
Even though fat oxidation is slow, fat molecules are large and energy dense. They are more complex than carbs, which slows their metabolism.
They can net significantly more ATP than glucose.
Glycolysis in the presences of o2:
Aerobic metabolism of glucose
Pyruvate in the presence of o2 enters the mitochondria and is converted into Acetyl-CoA, which enters the CAC and generates ATP.
Single glucose mol = 30 to 40 ATP.
Aminos and deamination: frequency & description
Aminos are rarely deaminated and converted to Acetyl-CoA.
Most times, when aminos are recruited as an energy source, they are first converted into glucose or ketones BECAUSE THERE ARE AAs that are either glucogenic or ketogenic, or both.
The glucogenics are built to convert into pyruvate, and subsequently glucose.
The ketogenics convert into ketone bodies.
The glucose & ketones enter their respective carb or fat based metabolic pathway.
Simplified CAC & ETC process
CAC: Breaks down Acetyl-CoA, yielding a few ATP, Co2 waste, and free electrons.
ETC: Receives the free electrons, driving a series of reactions yielding a greater number of ATP and water as a waste product.
Energy Systems & Exercise: flowchart
Low intensity, under vt1: fat oxidation
Quick burst of intensity: ATP-PC
Higher intensity, over vt1: glycolysis
Extended effort: fat oxidation returns primarily.
*All 3 systems in constant state of flux
Steady state aerobic exercise
Exe performed at a steady intensity, with stable HR & o2 consumption.
Excess post exercise oxygen consumption (EPOC)
Elevated o2 consumption that occurs a few mins after exercise in order to keep generating ATP aerobically.
The purpose of, is to restore ATP & CP above & beyond what is needed for recovery back to baseline, and to clear metabolic waste products.
o2 consumption will return to normal once ATP & CP levels have been restored.
Recommended Recovery Intervals
1:1 Ratio of work to rest
Recovery is an aerobic event to set ATP-PC levels back to normal and eliminate metabolic waste products.
*EPOC prevents the aerobic process to fully take over.
o2 deficit when exercise intensity is increased leads to what metabolic reactions?
The ATP-PC & Glycolytic Systems work to provide energy anaerobically, because aerobic metabolic pathways are too slow to meet energy demand.
ATP-PC characteristics: fuel substrate, exercise intensity supported, time to exhaustion, limiting factors
Fuel: PC (phosphocreatine)
Exe supported: rapid onset, high
Time to exhaust: 10-15s
Limiting factor: Depletion of ATP-PC stores.
Glycolytic System: characteristics: fuel substrate, exercise intensity supported, time to exhaustion, limiting factors
Fuel: Glucose
Exe supported: Moderate to high
Exhaustion: 30-60s plus
Limiting factors: anaerobic Lactate H-ion released & co2 accumulation
Oxidative System: characteristics: fuel substrate, exercise intensity supported, time to exhaustion, limiting factors
Fuel: Free Fatty Acids (& pyruvate in aerobic glycolysis)
Exe supported: Low to Moderate
Exhaustion: theoretically unlimited Impacted by fitness level.
Limiting factors: Insufficient o2; heat accumulation; & muscle fatigue.
“Fat Burning Zone” myth
Lower intensity activities use a higher percentage of fats as fuel, but they do not burn a lot of calories unless done for a long time.
Although higher intensity exe is fueled more by carbs/glucose, it burns a larger number of total cals (including more fat cals) and is therefore more efficient when training time matters
Total Daily Energy Expenditure (TDEE)
All cals burned in a day
Total of:
Resting Metabolic Rate (RMR) 60-70%
Exercise Activity Thermogenesis (EAT)
Thermic Effect of Food (TEF) 10% (protein has highest TEF)
Non-Exe Activity Thermogenesis (NEAT)
Kilocalorie (kcal)
One food cal as written incorrectly on food labels (c= energy needed to raise 1g of H2o 1 deg. C) (C, aka, kcal = 1000 cals energy needed to raise 1kg H2o 1 deg. C)
The amount of energy needed to raise ONE KG of water by ONE DEGREE C.
Resting Metabolic Rate (RMR)
The rate at which the body burns cals when fasted & at rest. Higher in people w/ more muscle mass. Underestimated in prediction equations like Katch-McArdle
About 70% of TDEE
Slightly higher than BMR (usually by 10%), since BMR is only the min. cals needed for basic functioning & doesn’t account for the cals ACTUALLY burned to ACHIEVE THESE BASIC FUNCTIONS.
Physical Activity Level (PAL)
The total number of cals burned through regular activity & structured exe.
TDEE divided by RMR
Higher number shows more active lifestyle
Shows number of cals burned while active compared to cals burned at rest.
Ideal ratios 1:1 to 1:2.5
Number of cals needed to use 1L of o2
5 cals
Metabolic Equivalent (MET)
A way to quantify activity based on o2 usage.
1 MET is the amount of o2 consumed at rest.
1 MET equals 3.5 mL of o2 consumed per kg of body weight per min, which is the avg RMR for most people.
Calculate average RMR
Find 1 MET:
(3.5 mL of o2/ body weight in kg) per min
Exe. 160lbs subject = 72.57kg
3.5/ 72.57 * 1440 mins = 69.45
