Week 2 - Bioenergetics and Exercise metabolism Flashcards
What is bioenergetics
Flow and exchange of energy within a living system
Conversion of foodstuffs (fats, proteins, carbohydrates) into usable energy for cell work. ‘Chemical → mechanical’
Implications for performance
What is metabolism
Sum of all chemical reactions that occur in the body
WHat are anabolic reactions
Synthesis of molecules
What are catabolic reactions
Breakdown of molecules
1st law of thermodynamics
Energy cannot be created or destroyed only transformed from one form to another
Whats the difference between endergonic and exergonic reactions
endergonic - requires energy to be added to the reactants
Exergonic - releases energy
What are coupled reactions
Liberation of energy in an exergonic reaction drives an endergonic reaction
Whats the difference between an oxidation and reduction reaction
Oxidation - removes an electron
Reduction - adds an electron
What are enzymes
proteins that lower the energy of
activation and accelerate chemical reactions
increase rate of product formation
What are the components of the anaerobic pathway
Does not involve oxygen (o2)
Phosphocreatine breakdown and glycolysis
What are the componenents of aerobic pathway
Requires oxygen
Oxidative phosphorylation
Dependent on respiratory and cardiovascular systems to deliver adequate o2
What are the 2 processes essnetial for ATP generation
Krebs cycle - Completes oxidation of acetyl CoA electrons for the electron transport chain
Electron transport chain - Energy obtain from electron transport is used to produce ATP at the end of the electron transport chain
Explain the process of the electron transport chain (ON SHEET)
- NADH & FAD are re-oxidized,
releasing high-energy electrons
from the hydrogen atoms. e-
are passed down a series of
electron carriers (cytochromes),
coupled with the pumping of H+
into the intermembrane space. - concentration of H+ ions in
the intermembrane space. - Movement of H+ through ATP
synthase produces ATP
How are bioenergetics controlled
Rare limiting enzymes which are found early in metabolic pathway, activity is regulated by modulators
What are the energy requirements at rest
Almosst 100% of ATP produced by aerobic metabolism
Blood lactate levels are low <1mmol/l
Resting o2 consumption - 0.25l/min (3.5ml/kg/min)
What are the rest to exercise transitions
ATP production increases immediately
Oxygen uptake increases rapidly
Initial ATP production must be through anaerobic pathways which creates an oxygen deficit
Why do endurance trained individuals have lower o2 deficit than untrained (ON SHEET)
Better developed aerobic bioenergetic capacity
Greater regional blood flow to active muscle
Increased cellular adaptation and efficiency
Increased mitochondrial volume in muscle fibers leads to less lactate production at beginning of exercise
How is oxygen impacted during recovery
Oxygen uptake remains elevated above rest during recovery from exercise
What is the main factor that influences magnitude and duration of EPOC
Intensity of exercise
What are the differnces between rapid and slow portion of EPOC
Rapid - re synthesis of stored PC in muscle (recovered in 60-120s)
Replenishes muscle and blood o2 stores
Slow - elevated HR to meet o2 demand
Elevated body temp
Elevated blood levels of epinephrine and norepeniphrine = increase metabolic rate
Conversion of lactic acid to glucose
What are the metabolic responses to exercise duration and intensity
Short term, high intensity exercise <5 secs, ATP produced via ATP-PC
Intense exercise >5 secs, shift to ATP production via glycolysis
Events lasting >45secs, ATP production through ATP-PC, glycolysis, and aerobic systems
50% anaerobic/50% aerobic at 2 mins
Prolonged exercise >10 mins, ATP production primarily from aerobic metabolism
What are the key aspects of carbohydrates as a fuel for exercise
Energy source - glucose
energyy yield - 4kcal/g
Stored form - Glycogen
Stored where - liver and muscle
Breakdown process - glycogenolysis
What are the key aspects of fats as a fuel for exercise
Energy source - fatty acids
Energy yield - -9kcal/g
Stored form - triglycerides
Stored where - muscle and adipose tissue
Breakdown process - Lipolysis
What are the key aspects of protein as a fuel for exercise
Energy source - amino acids
Energy yield - 4kcal/g
Contribues energy by gluconeogensis in liver and can be converted to metabolic intermediates
What are some of the caveats of using pulmonary gas exchanges as a means to estimate fuel utilisation
Measurement must be performed during steady-state exercise to reflect gases in tissues
Assumes that 0 protein is used as a fuel during exercise
What is the crossover concept
The shift from fat to CHO metabolism as exercise intensity increases
Why does the crossover concept take place
(ON SHEET)
Recruitment of fast muscle fibers (abundance of glycolytic enzymes, fewer
lipolytic enzymes)
Increasing blood levels of epinephrine stimulate glycolysis and lactate production (inhibits fat metabolism by reducing the availability of fat as a substrate
What are the 2 main factors that impact fuel selection during exericse
Exercise duration and exercise intensity
How does exercise duration impact fuel selection (ON SHEET)
An increased rate of lipolysis
Breakdwon of triglycerides -> glycerol and FFA
Stimulated by rising blood levels of several hormones
What is beta oxidation
Process of oxidising fatty acids to acetyl CoA
Why does glycogen get depleted during prolonged high-intensity exercise
(ON SHEET)
Decreased rate of glycolysis and production of pyruvate, decreased rate of krebs-cycle activity
What exercise intensity is best for burning fat ?
-20% Vo2 max:
- % of energy from fat = high 66%
- Total energy expenditure = Low 3kcal min-1
- Total fat oxidation = low 2kcal min-1
-60% vo2 max:
- % of energy from fat = lower 33%
- Total energy expenditure = higher 9kcal min-1
- total fat oxidation = higher 3kcal min-1
Impact of exercise intensity on fat metabolism (ON SHEET)
fat oxidation increases with energy intensity until 60% vo2 max intensity is reached then fat oxidation decreases with energy intensity
Whats the influence of exercise intensity on fuel source (ON SHEET)
The relative contribution of muscle glycogen and blood glucose varies
Increased rate of glycogenolysis due to recruitment of fast-twitch fibres and elevated blood epinephrine levels
Influence of exercise duration on fuel source
(ON SHEET)
Percentage of energy derived from the four major sources of fuel during prolonged submaximal exercise
Immediate energy sources in muscle depleted over time
Increased reliance on substrates in the blood
What are some potential explanations for the lactate threshold (ON SHEET)
Accelerated glcolysis
Recruitment of fast-twitch muscle fibers during intense rapid exercise - LDH isozyme has greater affinity for attaching to pyruvate promoting lactate formation
Reduced rate of lactate removal from the blood
Can lactate be used as a fuel source
Yes
Lactate shuttle - produced in one tissue and transported to another to be used as an energy source
Cori cycle - cycle of lactate/glucose between the muscle/liver
