Energy Metabolism in Muscle Flashcards
main fuel in exercising muscles?
glycogen, glucose, free fatty acids
energy at rest?
predominantly fatty acids
high intensity isometric exercise energy?
anaerobic glycolysis and creatine kinase
submaximal exercise, low intensity?
blood glucose and free fatty acid
submaximal, high intensity?
more from glycogen and glucose
-glycogen main source
fatigue?
when glucose and glycogen stores are depleted
first hour of mild, low intensity?
glucose, glucagon and free fatty acids
one to four hours mild to moderate prolonged exercise?
free fatty acids increase substantially
**after four hours, free fatty acids main source
what maintains ATP levels?
glycogen and glucose metabolism oxidative phosphorylation creating kinase purine nucleotide synthesis lipid metabolism
anaerobic glycolysis
high intensity, isometric activity
results in fatigue - increasead lactate - acidification
aerobic glycolysis
dynamic isotonic exercise
pyruvate > acetyl CoA > TCA Cycle
rate limiting step in glycolysis?
fructose 6 P to fructose 1,6 BP
-enzyme: PFK
oxidative phosphorylation
18x more ATP than glycolysis alone
phosphocreatine pathway
enzyme: creatine kinase
phosphocreatine + ADP > ATP + creatine
duration of reaction is very small
-first 2-7 seconds
where is creatinephosphate synthesized?
liver and transported to muscle cells via bloodstream
location of creatine kinase?
skeletal muscle, heart, brain
CK 1
CK BB in brain, smooth muscles of lungs
CK 2
CK MB in heart
CK 3
CK MM in skeletal muscle
CK in blood tests?
elevation can indicate: MI rhabdomyolysis muscular dystrophy acute renal failure drugs
purine nucleotide cycle
intensely exercising muscle can generate ATP over a short period using adenylate reaction
two ADP into ATP and AMP
fate of AMP
deaminated to IMP
enzyme: myoadenylate deaminase
- produced ammonia
higher in type 2 fast muscle fibers**
AMP deaminase?
AMP > IMP
releases ammonia
exercise induced myopathy and most common cause of metabolic myopathy?
deficiency in AMP deaminase
beta oxidation
of fatty acids
at rest - main energy substrate for muscles
what fatty acids can cross membrane?
less than 10 carbons
- can cross inner and outer mito membranes
- undergo beta oxidation
what happens with long chain fatty acids?
cannot cross mito membrane
activated by long chain acyl CoA synthetase
-to CoA thioester which crosses outer membrane
palmitoylcarnitine
transferred across inner mito membrane
-carnitine:acylcarnitine translocase
converted back to free acyl-CoA and carntine
-enzyme: CPT II
CPT I
combines acyl-CoA with carnitine
acylcarnitine can then be transferred across inner membrane
how does acylcarnitine get across inner membrane?
carnitine:acylcarnitine translocase
converted back to acyl-CoA (carnitine recycled outside)
acyl-CoA then is beta-oxidized
omega oxidation
of fatty acids
during prolonged fasting
-in liver peroxisome
forms DCAs which go through mitochondrial beta-oxidation
difference between beta ox and peroxisome ox
beta two separate enzymes
peroxisome ox one multifunction enzyme protein
zellweger syndrome
accumulation of long chain fatty acids
peroxisomal disorder
aderenoleukodystrophy
accumulation of long chain fatty acids
peroxisomal disorder
indicatin of omega ox?
DCAs in urine
inborn errors of fatty acid oxidation?
DCAs and acylglycine in urine
acylcarnitine derivatives in serum
cori cycle
recycles lactic acid
more efficient when muscle activity stops
oxygen debt can be made up
lactate > liver
-converted to pyruvate then to glucose (requires ATP)
what favors lactate production in skeletal muscle?
high NADH/NAD + ratio
intense exercise, increased lactate
drop in pH
-cramps
lactic acidosis sign of what?
MI
pulmonary embolism
uncontrolled embolism
uncontrolled hemorrhage
**any time we can’t get blood to tissue
regeneration of NAD+
done by lactate formation (anaerobic glycolysis)
primary carnitine deficiency syndrome
lack of carnitine within cell (carnitine transporter mutation)
-lipid myopathy
fatty acid oxidation significantly reduced**
secondary carnitine deficiency syndrome
carnitine sequestered in form of acyl-carnitine
-carnitine cannot be removed from acyl group
defect in ACT II
elevated levels of acyl carnitine
fatty acid oxidation significantly reduced**
fatty acid transport defects
CPT I
CPT II
carnitine:acylcarnitine translocase
mitochondrial defects
defects of beta-oxidation enzymes
myopathic symptomes that are usually progressive
oxidative phosphorylation system
main source of energy in muscles and other cells
fasting?
omega oxidation (DCA production)
