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
