Transcript Skeletal Muscle Metabolism

Skeletal Muscle Metabolism
How do muscles use energy?
WHAT
IS
Chemical compound used
to trap energy from food
ATP
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Mitochondria in muscle convert glucose,
fatty acids, and amino acids into ATP
ATP is used by the cell for any process that
requires energy (such as muscle
contraction)
The amount of oxygen available to the
muscle cells determines the amount of ATP
that can be produced
ATP
Adenine
P
P
P
3 Phosphate
groups
Ribose
ATP
Adenine
ENERGY
stored in
bonds
P
P
P
3 Phosphate
groups
Ribose
ADP
ATP
ATP
P
P
ENERGY
RELEASED
PP
Sources of ATP (times
approximate)
• Stored ATP from processes below (4-6
seconds worth)
• Creatine Phosphate (10 seconds)
• Glycogen (stored carbohydrates in liver and
muscle) or glucose in blood are used for
glycolysis and lactic acid fermentation (30-40
second bursts)
• Glycogen, glucose, fatty acids are used in
aerobic respiration (lasts for hours)
Glucose from
glycogen in
muscle
and liver
O2
Glycolysis
No O2
Summary: With or Without
Oxygen?
Without oxygen (anaerobic) With Oxygen (aerobic)
 Glycolysis (splitting of
 cellular respiration using
glucose) follow by
glucose, fatty acids, or amino
fermentation of lactic acid)
acids (preceded by glycolysis)
 ATP produced quickly
 ATP produced slowly
 Fewer ATP are generated
 More ATP generated
 Duration: 30-60 seconds
 Duration: hours
Muscle Fiber Types
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Slow-oxidative - endurance activities
(jogging) (smallest diameter)
Fast - oxidative - short term activities
requiring bursts of energy (sprinting,
basketball, soccer, etc.)
Fast-glycolytic - short intense
movements where force production is
maximal (lifting heavy weight, jumping,
throwing) (largest diameter)
• All muscles are a
mix of different fiber
types
• Genetics determine
the percentage of
different fiber types
in different muscle
Fatigue and Oxygen Debt
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Occurs when ATP demand is faster than
production (when O2 supply is limited)
Lactic acid “burn” limits usefulness of ATP
Oxygen Debt - the amount of O2 that must
be taken in to restore the muscles’ resting
conditions (ATP regeneration, glycogen
replenishment, creatine phosphate
restoration, lactate breakdown)
Muscle Fiber Ratios and Athletic
Performance
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Which of the above athletes have a greater
composition of fast twitch muscle fibers?
How does this relate to athletic performance?
Hypertrophy - increase in the size
of a muscle
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Micro-tears (of the myofilaments) create a stimulus for
hypertrophy.
Stressed fibers form more myofibrils, myofilaments (actin and
myosin), and store more glycogen (fast-twitch more prone to
growth)