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Exercise Physiology
Notes - Midterm
Chapter 2:
Bioenergetics
♥ Thermodynamics, energetics – science that studies the principles limiting energy exchange
♥ Bioenergetics – science that involves studies of energetic events in the biological world
Describing energy in the body:
♥ Energy is not created; it is acquired in one form and converted to another
♥ Conversion process is inefficient, and much of the energy released is in a no usable form – heat
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♥ Thermodynamics – physical science dealing with energy exchange
o More appropriate term is energetics
o 6 principal forms of energy: thermal, chemical, mechanical, electrical, radiant, and atomic
o Bioenergetics – branch of science that deals with energy exchanges in living things
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Biological engines cannot convert heat energy to other forms
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Temperature dependence
a
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The rates of biological or enzymatic reactions are sensitive to temperature
First Law of Thermodynamics – energy can be neither created nor destroyed
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Second Law of Thermodynamics – processes always go in the direction of randomness, or disorder
♥ Entropy – quantitative measure of disorder
o As a result of the 2nd law, entropy always increases
o Energy is exchanged, the efficiency of the exchange will be imperfect and some energy
will escape – usually in the form of heat – thus increasing entropy in the universe
o When one biological process moves some product toward a higher level of organization,
it is driven by at least one “linked” or “coupled” entropic reaction
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Energy Change (enthalpy ΔH) = Change in Energy available to do work + Change in unavailable
Energy(entropy)
Free Energy
♥ Free energy (G) – energy that is available, or free, to do the work; carries a -- sign
ΔH = ΔG + TΔS
Equilibrium – reaction has reached the end and entropy is at a maximum
♥ No longer any net change from reactant to product
♥ No further potential to do work
♥ Further from equilibrium the reactants of a process are, the more potential use the reaction has
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The metabolisms of ATP and CP are linked by the reaction governed by the enzyme creatine
kinase
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♥ Athletic activities : power, speed, endurance
o Skeletal system has three energy systems, each of which is used in each of these types of
activities
§ Power events – lasts a few seconds or less
• Immediate energy sources
§ Rapid, forceful exercises lasting from a few seconds to approximately 1 minute
o Nonoxidative, glycolytic energy sources
o Immediate sources
§ Activities lasting 2 minutes or more
o Oxidative mechanisms
Immediate Energy Sources
♥ In any myo contraction the degradation of ATP supplies the chemical energy to power the contraction
♥ Immediate energy source in muscle – 3 components
1
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Creatine Phosphate (CP)
§ Provides a reserve of phosphate energy to regenerate ATP
• Consumed as a result of myo contraction
• Interaction of CP and ADP (degraded ATP) is catalyzed by the enzyme creatine
kinase
• ATP that is hydrolyzed to ADP during muscle contraction is rephosphorylated by
CP
3
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Myokinase
• Ability to generate one ATP (and one AMP) from two ADPs