EXERCISE AND
NUTRITIONAL SCIENCES 632
PHYSIOLOGICAL CHEMISTRY OF
EXERCISE
Michael J. Buono, Ph.D.
Fred W. Kolkhorst, Ph.D.
San Diego State University
http://www-rohan.sdsu.edu/~ens632/
BIOENERGETICS
-how the body acquires, converts, stores, and
utilizes energy
First Law of Thermodynamics (conservation of energy)
energy cannot be created or destroyed, only converted from one form
(chemical, thermal, mechanical, light, etc) to another; thus, the total
energy in the universe remains constant. (examples: photosynthesis =
light to chemical, exercise = chemical to mechanical)
Second Law of Thermodynamics
whenever energy is exchanged between forms the exchange is
imperfect and some energy is lost as heat (randomness increases)
(humans are 25% efficient, 75% heat). Specific heat of the human
body is .83 kcal/kg/oC, thus a 60 kg person needs to retain 50 kcal of
heat (.83 x 60) to increase the core body temperature 1 oC. Thus,
running a mile (100 kcal) theoretically should increase the core body
temperature 2 oC if no heat was lost.
•
Exercise
Photosynthesis
Internal combustion
engine
Space heater
BIOENERGETICS (cont.)
• Exergonic Rx
– a reaction that gives up (releases) energy (burning of a
tree, hydrolysis of ATP, oxidation of carbohydrate, etc.)
• Endergonic Rx
– a reaction that absorbs (takes in) energy (growth of a
tree, resynthesis of ATP, formation of carbohydrate via
photosynthesis)
Coupled Reactions in Animals
• Exergonic Rx  ATP  Endergonic Rx
Oxidation of food  ATP  Muscular contraction, ion gradients
(CHO, Fat)
ATP (adenosine triphosphate)
• ATP need in rapidly contracting skeletal muscle is
over 100x greater than ATP need at rest.
ATP is needed for:
1.) myosin ATPase (50%)
2.) sarcoplasmic reticulum Ca++ ATPase (SERCA) (40%)
3.) Na+ /K+ ATPase (10%)
Sodium-Potassium ATPase
Humans have ECF [ Na+] of 140 mM and ICF [Na+] of 10 mM
Humans have ECF [ K+] of 4 mM and ICF [K+] of 150 mM
ExcitationContraction
Coupling
++
Ca cycling
Dihydropyridine (DHP) receptor
Ryanodine receptor
Sarcoplasmic Reticulum ATPase (SERCA)
Cross-bridge cycle - Myosin ATPase
ATP Structure
Electrostatic
repulsion
~ = phosphoanhydride
bond
ATP (cont.)
ATP + H20
ADP + Pi + H+ + free energy
Free Energy (-G) of ATP = -7.3 kcal/mole
exergonic reaction: thus (–) in value (products
have less free energy than reactants)
kcal = energy needed to raise 1L of water 1 C
mole = atomic wt. of substance in grams (6.02 x 1023
molecules)
Free energy(-G)
of various
biological
compounds
G and ATP
Early Studies on ATP
• Fletcher (1920s)  believed lactic acid caused
muscular contraction
• Embden (1920s)  rapid freezing of isolated
muscle showed contraction without HLA
formation
• Cain (1940s)  poisoned CPK with DNFB and
showed ATP decreased with each contraction thus
showing that hydrolysis of ATP provided the
energy needed for muscular contraction.
Substrate Level Phosphorylation
• PC + ADP + H
+
(-10.1 kcal/mole)  G
CPK
ATP + Cr
(-7.3 kcal/mole)  G
ATP Use During Exercise
CP and ATP Use During Exercise
Myokinase reaction 2 ADP
ATP + AMP
Changes in ATP,ADP and AMP
Amount of ATP needed to run a
Marathon