review pcr review glycolysis review tca hsl must stimulate the catabolism of triglyceride (glycerol...
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Review PCrReview PCr
Review GlycolysisReview Glycolysis
Review TCAReview TCA
HSL must stimulate the HSL must stimulate the catabolism of triglyceride catabolism of triglyceride
(glycerol + 3 FAs)(glycerol + 3 FAs) insulin (-)insulin (-) lactate (-)lactate (-) epi (+)epi (+) norepi (+)norepi (+) glucagon (+)glucagon (+) GH (+)GH (+) cortisol (+)cortisol (+)
If in adipose: glycerol may If in adipose: glycerol may enter circulation, be taken up enter circulation, be taken up by liver and phosphorylated to by liver and phosphorylated to
glycerol 3-phosphate glycerol 3-phosphate make new TGsmake new TGs enter the glycolytic pathwayenter the glycolytic pathway gluconeogenic precursor (via gluconeogenic precursor (via
dihydroxyacetone phosphate, DHAP)dihydroxyacetone phosphate, DHAP)
FAs can enter the muscle cell FAs can enter the muscle cell for further catabolizationfor further catabolization
Entry into cell no problem; Entry into cell no problem; entry into mitochondria for entry into mitochondria for Beta oxidation is similar to Beta oxidation is similar to
facilitated diffusion of glucose: facilitated diffusion of glucose: it takes othersit takes others
FAs are converted to a CoA FAs are converted to a CoA derivative by fatty acyl CoA derivative by fatty acyl CoA
synthasesynthase
Palmitate: 16C FA:Palmitate: 16C FA:
Palmitate Palmitate →→ palmitoyl CoA via long chain palmitoyl CoA via long chain acyl CoA synthaseacyl CoA synthase
ATP in and AMP out; net cost?ATP in and AMP out; net cost? now ready for beta oxidationnow ready for beta oxidation
Fatty acyl CoA must be Fatty acyl CoA must be transported across the mito. transported across the mito.
membrane and into the matrix membrane and into the matrix via carnitine shuttlevia carnitine shuttle
notice the “drop off” of CoA to combine with notice the “drop off” of CoA to combine with another fatty acyl CoAanother fatty acyl CoA
why supplement carnitinewhy supplement carnitine– increased carnitine, shuttle in more fat, more fat increased carnitine, shuttle in more fat, more fat
catabolism, even at restcatabolism, even at rest– partly b/c exercise causes an increased partly b/c exercise causes an increased
excretion of carnitine in urine, maybe lowering excretion of carnitine in urine, maybe lowering muscle levelsmuscle levels
no studies support this contention, need no studies support this contention, need mitochondria for carnitine to helpmitochondria for carnitine to help
NOW, beta oxidationNOW, beta oxidation
think of it as a merry-go round, dropping off think of it as a merry-go round, dropping off 2 carbons (acetyl CoA)2 carbons (acetyl CoA)
Two purposes of Beta OxidationTwo purposes of Beta Oxidation
cleave carbon atoms in pairs (acetyl CoA), cleave carbon atoms in pairs (acetyl CoA), degrading the FAdegrading the FA
produce high energy reducing equivalents, produce high energy reducing equivalents, NADH +H and FADHNADH +H and FADH22
Process of Beta oxidationProcess of Beta oxidation
most fats are 16 or 18 carbonsmost fats are 16 or 18 carbons
16C Palmitate:16C Palmitate:
5 ATP/ spin (n/2 - 1)5 ATP/ spin (n/2 - 1) 12 ATP/acetyl CoA (n/2)12 ATP/acetyl CoA (n/2) 7 spins X 5 = 35 ATP7 spins X 5 = 35 ATP 8 acetyl CoA X 12 = 96 ATP8 acetyl CoA X 12 = 96 ATP 35 + 96 = 131 ATP 35 + 96 = 131 ATP 2 ATP for activation, 131 - 2 = 129 ATP2 ATP for activation, 131 - 2 = 129 ATP
Uneven FAsUneven FAs
cleaving of pairs continues until last time, 2 cleaving of pairs continues until last time, 2 C and a 3CC and a 3C
3C fatty acid is propionyl CoA3C fatty acid is propionyl CoA propionyl CoA is converted to succinyl CoApropionyl CoA is converted to succinyl CoA
Glycerol catabolism: 19 ATPGlycerol catabolism: 19 ATP
Entire TGEntire TG
129 X 3 (3 FAs) = 387129 X 3 (3 FAs) = 387 387 + 19 (glycerol) = 406 ATP387 + 19 (glycerol) = 406 ATP
Acetyl CoA from Beta Acetyl CoA from Beta Oxidation must interact with Oxidation must interact with OXA to feed the TCA (CHO OXA to feed the TCA (CHO
flame)flame)
Acetyl CoA may be converted Acetyl CoA may be converted to ketones when not enough to ketones when not enough OXA (fasting, diabetes, and OXA (fasting, diabetes, and
prolonged exercise)prolonged exercise)
Ketones (or ketone bodies)Ketones (or ketone bodies)
two acetyl CoA condense to acetoacetatetwo acetyl CoA condense to acetoacetate acetoacetate reduced to 3-hydroxybutyrate acetoacetate reduced to 3-hydroxybutyrate
(if NADH:NAD ratio is high in mitochondria)(if NADH:NAD ratio is high in mitochondria) or, acetoacetate spontaneously, slowly or, acetoacetate spontaneously, slowly
undergoes a decarboxylation to acetoneundergoes a decarboxylation to acetone
this occurs in liverthis occurs in liver ketones may be used for energy, especially ketones may be used for energy, especially
by heart and kidneysby heart and kidneys
Fat catabolism during low Fat catabolism during low intensity exerciseintensity exercise
low intensity: 5 kcal/minlow intensity: 5 kcal/min
most (72%) derived from fatmost (72%) derived from fat 3.6 kcal from fat, 0.4 gms of fat3.6 kcal from fat, 0.4 gms of fat
double intensity: 10 kcal/mindouble intensity: 10 kcal/min
45% of energy is derived from fat45% of energy is derived from fat 4.5 kcal/min, 0.5 gm of fat4.5 kcal/min, 0.5 gm of fat
e.g., 5 kcal/min for 60 min = (5 e.g., 5 kcal/min for 60 min = (5 X 60) = 300 kcals, 24 gm fatX 60) = 300 kcals, 24 gm fat
10 kcal/min for 45 min = 450 10 kcal/min for 45 min = 450 kcals, 22.5 gm fatkcals, 22.5 gm fat
Therefore, should you Therefore, should you encourage some one to encourage some one to
exercise at low intensity to exercise at low intensity to “burn more fat”?????“burn more fat”?????
Fat facts:Fat facts:
fat utilization decreases when exercise fat utilization decreases when exercise follows a high CHO meal (increase in follows a high CHO meal (increase in circulating insulin)circulating insulin)
fat utilization decreases when lactate begins fat utilization decreases when lactate begins to accumulateto accumulate
ability to use fat as a fuel increases with ability to use fat as a fuel increases with trainingtraining