Week 2 - Bioenergetics and Exercise metabolism Flashcards

1
Q

What is bioenergetics

A

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

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2
Q

What is metabolism

A

Sum of all chemical reactions that occur in the body

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3
Q

WHat are anabolic reactions

A

Synthesis of molecules

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4
Q

What are catabolic reactions

A

Breakdown of molecules

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5
Q

1st law of thermodynamics

A

Energy cannot be created or destroyed only transformed from one form to another

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6
Q

Whats the difference between endergonic and exergonic reactions

A

endergonic - requires energy to be added to the reactants
Exergonic - releases energy

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7
Q

What are coupled reactions

A

Liberation of energy in an exergonic reaction drives an endergonic reaction

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8
Q

Whats the difference between an oxidation and reduction reaction

A

Oxidation - removes an electron
Reduction - adds an electron

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9
Q

What are enzymes

A

proteins that lower the energy of
activation and accelerate chemical reactions
increase rate of product formation

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10
Q

What are the components of the anaerobic pathway

A

Does not involve oxygen (o2)
Phosphocreatine breakdown and glycolysis

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11
Q

What are the componenents of aerobic pathway

A

Requires oxygen
Oxidative phosphorylation
Dependent on respiratory and cardiovascular systems to deliver adequate o2

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12
Q

What are the 2 processes essnetial for ATP generation

A

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

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13
Q

Explain the process of the electron transport chain (ON SHEET)

A
  1. 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.
  2. concentration of H+ ions in
    the intermembrane space.
  3. Movement of H+ through ATP
    synthase produces ATP
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14
Q

How are bioenergetics controlled

A

Rare limiting enzymes which are found early in metabolic pathway, activity is regulated by modulators

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15
Q

What are the energy requirements at rest

A

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)

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16
Q

What are the rest to exercise transitions

A

ATP production increases immediately
Oxygen uptake increases rapidly
Initial ATP production must be through anaerobic pathways which creates an oxygen deficit

17
Q

Why do endurance trained individuals have lower o2 deficit than untrained (ON SHEET)

A

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

18
Q

How is oxygen impacted during recovery

A

Oxygen uptake remains elevated above rest during recovery from exercise

19
Q

What is the main factor that influences magnitude and duration of EPOC

A

Intensity of exercise

20
Q

What are the differnces between rapid and slow portion of EPOC

A

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

21
Q

What are the metabolic responses to exercise duration and intensity

A

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

22
Q

What are the key aspects of carbohydrates as a fuel for exercise

A

Energy source - glucose
energyy yield - 4kcal/g
Stored form - Glycogen
Stored where - liver and muscle
Breakdown process - glycogenolysis

23
Q

What are the key aspects of fats as a fuel for exercise

A

Energy source - fatty acids
Energy yield - -9kcal/g
Stored form - triglycerides
Stored where - muscle and adipose tissue
Breakdown process - Lipolysis

24
Q
A
25
Q

What are the key aspects of protein as a fuel for exercise

A

Energy source - amino acids
Energy yield - 4kcal/g
Contribues energy by gluconeogensis in liver and can be converted to metabolic intermediates

26
Q

What are some of the caveats of using pulmonary gas exchanges as a means to estimate fuel utilisation

A

Measurement must be performed during steady-state exercise to reflect gases in tissues
Assumes that 0 protein is used as a fuel during exercise

27
Q

What is the crossover concept

A

The shift from fat to CHO metabolism as exercise intensity increases

28
Q

Why does the crossover concept take place
(ON SHEET)

A

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

29
Q

What are the 2 main factors that impact fuel selection during exericse

A

Exercise duration and exercise intensity

30
Q

How does exercise duration impact fuel selection (ON SHEET)

A

An increased rate of lipolysis
Breakdwon of triglycerides -> glycerol and FFA
Stimulated by rising blood levels of several hormones

31
Q

What is beta oxidation

A

Process of oxidising fatty acids to acetyl CoA

32
Q

Why does glycogen get depleted during prolonged high-intensity exercise
(ON SHEET)

A

Decreased rate of glycolysis and production of pyruvate, decreased rate of krebs-cycle activity

33
Q

What exercise intensity is best for burning fat ?

A

-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

34
Q

Impact of exercise intensity on fat metabolism (ON SHEET)

A

fat oxidation increases with energy intensity until 60% vo2 max intensity is reached then fat oxidation decreases with energy intensity

35
Q

Whats the influence of exercise intensity on fuel source (ON SHEET)

A

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

36
Q

Influence of exercise duration on fuel source
(ON SHEET)

A

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

37
Q

What are some potential explanations for the lactate threshold (ON SHEET)

A

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

38
Q

Can lactate be used as a fuel source

A

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