BIOC/DENT/PHCY 230
LECTURE 3
Fatty acids as a fuel
Fatty acids are the preferred fuel for most tissues
Fatty acids can only be metabolised aerobically
Red blood cells can’t use fatty acids as they don’t have mitochondria
Neurons can’t use fatty acids as they are unable to cross the blood brain barrier
Albumin-ffa
tissues
passive
Delivery of fatty acids for fuel
FABP-ffa
FABP = fatty acid binding protein
Transport across cell membrane
Fatty acid activationFatty acids are activated for
oxidation by attachment to CoA
R-COO-+ATP+CoA-SH R-C-S-CoA +AMP + PPi
O
G0’= -0.8kJ/molfatty acyl-CoA
Transport into mitochondria
-Oxidation
Regulation of -oxidation
In general, the catabolism of fatty acids is regulated by supply
In muscle, the availability of substrates for -oxidation can be controlled at several points:
1) Transport across the sarcolemma
2) Transport into the mitochondria
3) Hydrolysis of local fat stores
1) Transport across the sarcolemma
FABPpm FAT (fatty acid translocase)
after fasting
with exercise
can translocate to membrane from vesicles
translocation stimulated by muscle contraction
2) Transport into the mitochondria
CPT1
CPT1
3) Hydrolysis of local fat stores
Intra-MuscularTriacylGlycerols (IMTGs)
Degraded by hormone sensitive lipase (HSL)
Energy yield from the oxidation of palmitate (16:0)
Aerobic oxidation of glucose: ~36 ATP
Exercise Metabolism
Exercise puts significant energy demands on the body
Different types of exercise require the mobilisation and differential processing of different fuels
Tissue needs during exercise can be met by:
1) intracellular high energy molecules
2) local stores of fuel macromolecules
3) remote stores of fuel macromolecules
4) synthesis of fuel molecules in certain tissues
ATP can be generated by several metabolic pathways
during exerciseGlycolysis (aerobic and anaerobic)
-oxidation
Creatine phosphate
creatine phosphate + ADP creatine + ATP
G ~ 0
CK
CK = creatine kinase
Fuel use is related to exercise intensity
The take home message: Fatty acids are a widely used fuel
Fatty acids are catabolised by -oxidation to yield acetyl-CoA
-oxidation is mainly regulated by the delivery of substrate
Exercise increases the requirement for ATP Different types of exercise utilise different energy producing pathways
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