Unformatted text preview: ntraction depends on ATP supply.
Stimulus! ATP is needed to break the myosin-actin bonds,
and “re-cock” the myosin heads. To maintain contraction, actin–myosin bonds have
to keep cycling. Stimulus! ! Sources of ATP Muscle cells have three sources of ATP Muscles have three systems for obtaining ATP: Creatine-P
fatty acids Glycogen ! ! • Immediate system uses preformed ATP and
• Glycolytic system metabolizes carbohydrates to
lactic acid and pyruvate ATP ! • Oxidative system metabolizes carbohydrates and
fatty acids to H2O and CO2
contraction ! Supplying Fuel for High Performance Sources of ATP
ATP/CP ! ! Oxidative
! ! Immediate System: • Muscles contain creatine phosphate (CP) which
stores energy in a phosphate bond that can
transfer to ADP • Immediate system = ATP + CP. This system is
exhausted within seconds. ! Creatine phosphate as an “immediate buffer” for ATP
100 m world
seconds! Creatine! Creatinephosphate! Creatine
! ATP ! Sources of ATP Sources of ATP ! The glycolytic system ! Oxidative phosphorylation: • Enzymes are in the cytoplasm (sarcoplasm).
• ATP generated is directly available to myosin (fast). • Produces large amounts of ATP. • Anaerobic. • Aerobic. • Not very efficient (low ATP yield). • Occurs in mitochondria. • Lactic acid accumulates. • ATP must diffuse from mitochondria to the • Immediate and glycolytic systems provide energy for
less than one minute. myosin in the cytoplasm (slower than other two
! ! What Determines Muscle Strength and Endurance? What Determines Muscle Strength and Endurance? ! Slow-twitch muscle fibers:
There are two main types of skeletal muscle fibers:...
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- Winter '08