Bioenergetics/Fundamentals of Human Energy Transfer Flashcards
Define energy
- the body’s capacity to extract energy from food nutrients & transfer it to the contractile elements in skeletal muscle determines our capacity to move
1st law of thermodynamics
- energy cannot be created nor destroyed, but transformed from one form to another without being depleted
Describe potential & kinetic energies in the body
- constitute the total energy of a system
- releasing potential energy transforms the basic ingredient into kinetic energy of motion
Define exergonic reaction
- any physical or chemical process that releases energy to its surroundings
Define endergonic reaction
- chemical processes store or absorb energy
2nd law of thermodynamics
- tendency of potential energy to convert to kinetic energy of motion with a lower capacity for work
- ultimately, all of the potential energy in a system degrades to the unstable form of kinetic or heat energy
What are 3 forms of biologic work
Mechanical work: muscle contraction
Chemical work: synthesis cellular molecules
Transport work: concentration of various substances in the intracellular & extracellular fluids
Equation for cellular respiration
Glucose + 6O2 –> 6CO2 + 6H2O + ATP
What factors affect bioenergetics
- enzymes
- reaction rates
- mode of action
- coenzymes
Define enzyme
- a highly specific & large protein catalyst that accelerates the forward & reverse rates of chemical reactions within the body without being consumed or changed in the reaction
Define reaction rate
- operation rate of enzymes
Define mode of action
- how an enzyme interacts with its specific substrate
Define coenzymes
- complex nonprotein that facilitate enzyme action by binding the substrate with its specific enzyme
What are the cells’ 2 major energy transforming activities
- form & conserve ATP from food’s potential energy
- use energy extracted from ATP to power all forms of biologic work
How much ATP does the body store
- 80 to 100 grams
How much energy does the 80-100 grams of stored ATP provide
- provides enough intramuscular stored energy for several seconds of explosive all out exercise
Describe phosphocreatine (PCr)
- provides energy for ATP resynthesis
- releases a large amount of energy when the bond splits between the creatine & phosphate molecules
- cells store PCr in larger amounts than ATP
When does hydrolysis of PCr begin
- begins at the onset if intense exercise
- does not require oxygen
- reaches a max in about 8-12 secs
What is the fastest energy reaction/source
- phosphocreatine reaction
ATPase equation reaction
ATP <–> ADP + Pi + Energy
Creatine Kinase equation reaction
PCr + ADP <–> Cr + ATP
Define phosphorylation
- the energy transfer through the phosphate bonds of ATP to other compounds to raise them to a higher activation level
Define oxidation
- biologic burning of macronutrients in the body for the energy needed for phosphorylation
Describe oxidation
- occurs on the inner lining of mitochondrial membranes
- involves transferring electrons from NADH & FADH2 to molecular oxygen, which release & transfer chemical energy to combine ATP from ADP & phosphate
More than 90% of ATP synthesis takes place in the respiratory chain by oxidative reactions coupled with phosphorylation (True/False)
- True
What does oxygen combine with during aerobic ATP resynthesis
- combines with hydrogen to form water
What product has the highest potential energy and the lowest potential energy
Highest: NADH + H+
Lowest: H2O
Are electrons loss or gained during oxidation and reduction
Oxidation: electrons are loss (OIL)
Reduction: electrons are gained (RIG)
Macronutrient fuel sources for oxidation
- triacylglycerol & glycogen molecules stored within muscle cells
- blood glucose
- free fatty acids
- carbon skeletons of amino acids
- anaerobic reactions in the cytosol in the initial phase of glucose or glycogen breakdown
- phosphorylation of ADP by PCr
Describe carbohydrate energy release
- supplies energy for cellular work
- the only macronutrient whose potential energy generates ATP anaerobically
The complete breakdown of 1 mole of glucose into carbon dioxide, water, & heat yields a max of how many kCal
- max of 686 kCal of chemical free energy available for work
How many ATP molecules does the oxidation of 1 glucose molecule yield
- yields a total of 32 ATP molecules
Which macronutrients cannot be used for energy without oxygen
- fats
- proteins
Which macronutrient can be used for energy without oxygen
- carbohydrates
Define glycolysis
- carbohydrate breakdown
Describe aerobic glycolysis
- relatively slow process resulting in substantial ATP formation
- the 2nd stage of carbohydrate breakdown converts pyruvate to acetyl-CoA, which then progresses through the citric acid cycle
Describe anaerobic glycolysis
- rapid but limited ATP production that produces lactate as the end product
How many ATP does aerobic glycolysis yield
- 32 ATP
How many ATP does anaerobic glycolysis yield
- 4 ATP
What is required for pyruvate to convert to acetyl-CoA and continue into the citric acid cycle
- oxygen must be present and available
What is the most plentiful source of potential energy
- stored fat
How many ATP does the breakdown of 1 triacylglycerol molecule yield
- about 460 ATP molecules
- takes a lot of time
What are the 3 energy sources for fat catabolism
- triacylglycerols stored directly within the muscle fiber close to the mitochondria
- circulating triacylglycerols in lipoprotein complexes that become hydrolyzed on the surface of a tissue’s capillary endothelium
- adipose tissue that provides circulating free fatty acids mobilized from triacylglycerols in adipose tissue
Fats burn in a carbohydrate flame concept
- when carbohydrate level decreases, the oxaloacetate level may become inadequate, reducing fat catabolism
Describe protein energy release
-when deamination removes nitrogen from an amino acid molecule, the remaining carbon skeleton can enter metabolic pathways to produce ATP aerobically
- protein acts as an energy substrate during long duration endurance type activities
Fats and the metabolic mill
- fatty acids can either enter into beta oxidation or glycolysis
- if it enters into beta oxidation it turns into acetyl-CoA and goes through the citric acid cycle
Carbohydrates and the metabolic mill
- glucose & glycogen go through glycolysis and turn into pyruvate
- pyruvate forms acetyl-CoA and enters the citric acid cycle
Proteins and the metabolic mill
- amino acids go through deamination and form alanine, glycine, or ammonia
- ammonia turns to urine
- glycine forms acetyl-CoA and enters the citric acid cycle
- alanine forms pyruvate, which then forms acetyl-CoA, which then enters the citric acid cycle
What is an immediate energy system
- seconds
- ATP-PCr
What is a short term energy system
- 2-3 minutes
- lactic acid system
- anaerobic glycolysis
- uses lactate from breaking down glucose
What is a long term energy system
- aerobic system/glycolysis
- kreb cycle
Describe the ATP-PCr system
- used during short duration & high intensity activities (100m sprint)
- creatine kinase regulates the rate of phosphates breakdown
The quantity of intramuscular phosphagens substantially influences “all-out” energy for brief durations (True/False)
- True
Describe the lactic acid system
- during intense exercise, intramuscular stored glycogen provides energy to phosphorylate ADP during glycogenolysis, forming lactate
- performances of short duration & high intensity that require rapid energy transfer that exceeds that supplied by phosphagens (400m sprint, 100m swim, multi-sprint sports)
When does blood lactate threshold occur in healthy untrained individuals
- about 55% of their maximal capacity for aerobic metabolism
What are the ways the body can get rid of lactate
- transporting it to other muscles or organs with O2 to convert into pyruvate
- stopping the intense exercise to allow O2 to become present to convert lactate into pyruvate
Only exercise at higher intensities produces lactate accumulation (True/False)
- True
Factors related to lactate threshold
- low tissue oxygen
- reliance on glycolysis
- activation of fast twitch muscle fibers
- reduced lactate removal
Describe lactate shuttling
- lactate produced through glycogenolysis in one cell may be shuttled to another cell to provide fuel for further oxidation
What tissue is a major site of lactate production & removal
- skeletal muscle via oxidation for lactate removal
What tissue also accepts muscle generated lactate from the bloodstream
- liver & it synthesizes it to glucose
What reactions provide for the greatest portion of energy transfer
- aerobic metabolic reactions
What does the flat portion/plateau of the oxygen uptake curve represent
- represents the steady rate of aerobic metabolism
Describe oxygen uptake during exercise
- O2 uptake increases rapidly during the first minutes of exercise & reaches a relative plateau between minutes 4 & 6 & then remains relatively stable throughout the remainder of exercise
Describe oxygen deficit
- it represents the difference between the total oxygen consumed during exercise & an additional amount that would have been consumed had a steady-rate aerobic metabolism occurred immediately at the initiation of exercise
What does it mean for a trained individual to have a smaller oxygen deficit
- this indicates they consume more total oxygen during exercise with a proportionately smaller anaerobic energy transfer component
Define maximal oxygen uptake
- the highest oxygen uptake achieved despite increases in exercise intensity
What indicates an individual’s capacity to anaerobically resynthesis ATP
- VO2 max
When are fast twitch/type II muscle fibers used
- used during change of pace & stop and go activities, increased force output, or during all out effort requiring rapid powerful movements
Describe slow twitch/type I muscle fibers
- generates energy primarily aerobically
- possesses relatively slow contraction speeds
- used during continuous activites
What determines the energy system & metabolic mixture predominately used during exercise
- intensity
- duration
What system & fuel source predominates during low intensity exercise
- aerobic system
- fat
Does the liver (increase or decrease) the release of glucose to muscle as exercise progresses from low to high intensity
- increase
Describe oxygen debt
- recovery oxygen uptake or excess post exercise oxygen consumption (EPOC) defined as the excess oxygen uptake above the resting level in recovery
- the total oxygen consumed after exercise in excess of a pre-exercise baseline level
Factors affecting excess post-exercise oxygen consumption (EPOC)
- resynthesis of ATP & PCr
-resynthesis of blood lactate to glycogen - oxidation of blood lactate in energy metabolism
- restoration of oxygen to blood, tissue fluids, & myoglobin
- thermogenic effects of elevated core temperature
- increased pulmonary & circulatory dynamics & other elevated levels of physiologic function
Fast component of excess post-exercise oxygen consumption (EPOC)
- in low intensity aerobic exercise about half of the total EPOC occurs within 30 secs & complete recovery requires several minutes
Slow component of excess post-exercise oxygen consumption (EPOC)
-a second slower phase occurs in recovery from more strenuous exercise that may require 24 hours or more to complete full recovery
What occurs during recovery form steady rate exercise
- resynthesis of high energy phosphates
- replenishment of oxygen in the blood
- replenishment of bodily fluids
- replenishment of muscle myoglobin
- resupply of the small energy cost to sustain an elevated circulation & ventilation
Optimal recovery from non-steady rate exercise
- active aerobic exercise in recovery accelerates lactate removal
- 30-45% of VO2 max for bicycle exercise
- 55-60% of VO2 max for treadmill running
Define interval training
- exercising at an intensity that normally proves exhausting within 3-5 minutes using pre-established spacing of exercise to rest intervals
