Week 2 - Bioenergetics and Exercise Metabolism Flashcards
Bioenergetics
Flow and exchange of energy within a living system.
The conversion of food (fats, proteins, carbohydrates) into usable energy for cell work (chemical –> mechanical).
Metabolism
sum of all the chemical reactions that occur in the body (anabolic and catabolic).
Explain the two types of reactions in the body.
1) Anabolic reactions: synthesis of molecules (glucose being stores as glycogen)
2) Catabolic reactions: release of chemical energy through the breakdown of molecules to simpler molecules (glycogen broken down into glucose)
What is the difference between endergonic and exergonic chemical reactions?
Endergonic
> requires energy to be added to the reactants
> Ex: Glycogen formation or ATP synthesis
> Overall increase in energy
> Energy in products greater than reactants
Exergonic
> releases energy
> Ex: ATP hydrolysis
> Overall decrease in energy
> Energy in reactants greater than products
Coupled reactions
Liberation of energy in an exergonic reaction drives an endergonic reaction.
Oxidation and oxidised electron carriers
Oxidation is the loss of electron (OIL)
Oxidised electron carriers include NAD+ and FAD
Reduction and reduced electron carriers
Reduction is the gain of electrons (RIG)
Reduced electron carriers include NADH and FADH2
Enzymes
They act as catalyst in chemical reactions in the body by lowering the activation energy required for a reaction to occur (They increase the rate of product formation.)
Match the classification of enzyme with the description.
Kinase, dehydrogenases, oxidases, isomerases
a) Remove hydrogen atoms
b) Catalyze oxidation-reduction reactions involving oxygen
c) Rearrangement of the structure of molecules
d) Add a phosphate group
A = Dehydrogenases
B = Oxidases
C = Isomerases
D = Kinase
How does cellular environment factors influence enzyme activity during exercise?
Temperature - exercise increases temp slightly which improves enzyme activity, but after 40degrees enzymes become denatured.
pH - exercise produces H+ ions which reduces pH and inhibits enzyme activity with roles in ATP production.
Describe the two pathways that produce ATP and how they differ.
Anaerobic pathway (substrate-level phosphorylation) - doesn’t involve oxygen, ATP-PC system and glycolysis (leading to lactate).
Aerobic pathway - requires oxygen, oxidative phosphorylation, fat and carb oxidation, dependent on cardiorespiratory system to deliver adequate oxygen.
What is the net gain of glycolysis if
a) glucose is the substrate
b) glycogen is the subtsrate
a) 2ATP, 2NADH, 2 pyruvate/lactate, 2H+
b) 3ATP, 2NADH, 2 pyruvate/lactate, 2H+
Glycogen in the muscle doesnt require phosphorylation by ATP but is phosphorylated by inorganic phosphate instead.
How is NAD+ reformed?
In the absence of oxygen, pyruvate is converted into lactate (PDH) and tis allows the recycling of NAD+ that allows glycolysis to continue.
Describe the Citric acid cycle (Krebs cycle/TCA cycle) and list the products.
completes the oxidation (removes electrons) of acetyl-coa (formed from fuels: fats, CHO, protein) to provide electrons for the ETC.
Products of x1 Acetyl-CoA = ATP, 1FADH2, 3NADH, 4H+, 2CO2, CoA
Aerobic ATP production
32 ATP (38ATP)
Amount of ATP produced
a) per NADH
b) per FADH
a) 2.5ATP per NADH
b) 1.5ATP per FADH
Define oxygen deficit and explain how it’s created?
Discrepancy between initial demand for oxygen and the amount of available oxygen (O2 uptake).
This is created as the initial ATP production during exercise is through anaerobic pathways but as we reach steady-state (1-4mins) ATP production is primarily aerobic.
Excess post-exercise oxygen consumption (EPOC)
oxygen uptake remains elevated above rest during recovery from exercise.
What is the magnitude and duration of EPOC influenced by?
the intensity of exercise
Rate limiting enzymes
- Where are they found?
- What is activity regulated by?
- Examples
- Found early in a metabolic pathway
- Activity is regulated by modulators
- Ex: creatine kinase for ATP-PC system / phosphofructokinase for glycolysis
3 reasons why endurance trained individuals have a lower 02 deficit than untrained individuals.
1) Greater regional blood flow to active muscle (e.g. more capillaries)
2) Increased cellular adaptation and efficiency
3) Increased mitochondrial volume in muscle fibers results in less lactate production at the beginning of exercise
Briefly outline the components of the slow and fast (rapid) components of EPOC
Fast (alactacid) component of EPOC: resynthesis of energy sources such as ATP and phosphocreatine.
Slow (lactacid) component of EPOC: includes elevated HR, BR, body temp, E/NE and conversion of lactic acid to glucose. Muscle repair up to 12hrs after.
Explain the basic concept of enzyme action.
The substrate binds to the enzyme active site to form an Enzyme-substrate complex.
The enzyme then catalyses the reaction and the products are released from the unaltered enzyme molecule.
What does phosphorylation enable?
the coupling of an exergonic reaction to an endergonic one
Explain the conversion of pyruvate to acetyl-coa.
Once in the mitochondria:
» Pyruvate is oxidised by NAD+, producing NADH + H+ (reduced form), and decarboxylated, producing a molecule of CO2 and a 2-carbon fragment of acetate bound to coenzyme A which forms acetyl-coa.
Briefly describe the Electron transport chain.
NADH and FADH2 are re-oxidised releasing electrons and hydrogen atoms. Electrons then pass down a series of electron carriers which provides the energy for H+ to be pumped into the intermembrane space.
Where is energy that is liberated from chemical bonds through metabolism stored?
- most is stored in ATP in skeletal muscle and to a lesser extent the brain
- some is stored in phosphocreatine
For each molecule of glucose metabolized, how many molecules of 02 and C02 are produced?
6 molecules of C02 released from organic compounds.
6 molecules of H20 formed through the electron transport chain - this requires utilisation of 6 molecules of 02.
RER is 1
A high level of __ in the muscle fiber would slow glycolysis by inhibiting its rate of limiting enzyme.
ATP
Glycolysis
- The breakdown of glucose/glycogen into two molecules of pyruvate or lactate.
- Occurs in the cytosol
At rest, what is the O2 consumption of a young adult? Using this answer, what would the oxygen consumption of a 70-kg adult be?
3.5 ml-kg-min
250ml/min OR 0.25L/min
Where does most of the carbohydrate used as a substrate during high-intensity exercise come from?
muscle glycogen stores
Identify the 3 possible mechanisms to explain the lactate threshold.
1) Accelerated rate of glycolysis due to epinephrine
2) Recruitment of fast-twitch muscle fibers
3) Reduces rate of lactate removal from the blood
What gland is epinephrine released from?
adrenal medulla
How can the depletion of muscle carb stores during exercise decrease the ability of the muscle to metabolize fat?
reduces the concentration of citric acid cycle intermediates
Identify 3 factors by which blood glucose concentration is maintained fairly constant during exercise.
1) Elevated mobilization of FFA from adipose tissue
2) Increased rate of gluconeogenesis
3) Blocked entry of glucose into cells
