Week 2 - Bioenergetics and Exercise metabolism

Question 1

What is bioenergetics

Answer 1

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

Question 2

What is metabolism

Answer 2

Sum of all chemical reactions that occur in the body

Question 3

WHat are anabolic reactions

Answer 3

Synthesis of molecules

Question 4

What are catabolic reactions

Answer 4

Breakdown of molecules

Question 5

1st law of thermodynamics

Answer 5

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

Question 6

Whats the difference between endergonic and exergonic reactions

Answer 6

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

Question 7

What are coupled reactions

Answer 7

Liberation of energy in an exergonic reaction drives an endergonic reaction

Question 8

Whats the difference between an oxidation and reduction reaction

Answer 8

Oxidation - removes an electron
Reduction - adds an electron

Question 9

What are enzymes

Answer 9

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

Question 10

What are the components of the anaerobic pathway

Answer 10

Does not involve oxygen (o2)
Phosphocreatine breakdown and glycolysis

Question 11

What are the componenents of aerobic pathway

Answer 11

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

Question 12

What are the 2 processes essnetial for ATP generation

Answer 12

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

Question 13

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

Answer 13

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

Question 14

How are bioenergetics controlled

Answer 14

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

Question 15

What are the energy requirements at rest

Answer 15

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)

Question 16

What are the rest to exercise transitions

Answer 16

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

Question 17

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

Answer 17

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

Question 18

How is oxygen impacted during recovery

Answer 18

Oxygen uptake remains elevated above rest during recovery from exercise

Question 19

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

Answer 19

Intensity of exercise

Question 20

What are the differnces between rapid and slow portion of EPOC

Answer 20

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

Question 21

What are the metabolic responses to exercise duration and intensity

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 25

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

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What is the crossover concept

Answer 27

The shift from fat to CHO metabolism as exercise intensity increases

Question 28

Why does the crossover concept take place
(ON SHEET)

Answer 28

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

Question 29

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

Answer 29

Exercise duration and exercise intensity

Question 30

How does exercise duration impact fuel selection (ON SHEET)

Answer 30

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

Question 31

What is beta oxidation

Answer 31

Process of oxidising fatty acids to acetyl CoA

Question 32

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

Answer 32

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

Question 33

What exercise intensity is best for burning fat ?

Answer 33

-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

Question 34

Impact of exercise intensity on fat metabolism (ON SHEET)

Answer 34

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

Question 35

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

Answer 35

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

Question 36

Influence of exercise duration on fuel source
(ON SHEET)

Answer 36

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

Question 37

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

Answer 37

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

Question 38

Can lactate be used as a fuel source

Answer 38

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