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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
Delivery of fatty acids for fuel
Albumin-ffa
passive
tissues
Transport across cell membrane
FABP-ffa
FABP = fatty acid binding protein
Fatty acid activation
Fatty acids are activated for
oxidation by attachment to CoA
O
R-COO-+ATP+CoA-SH
fatty acyl-CoA
R-C-S-CoA +AMP + PPi
DG0’= -0.8kJ/mol
Transport into mitochondria
b-Oxidation
Regulation of b-oxidation
In general, the catabolism of fatty acids
is regulated by supply
In muscle, the availability of substrates
for b-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
after fasting
with exercise
FAT (fatty acid translocase)
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-Muscular
TriacylGlycerols (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 exercise
Glycolysis (aerobic and anaerobic)
b-oxidation
Creatine phosphate
creatine phosphate + ADP
CK = creatine kinase
CK
creatine + ATP
DG ~ 0
Fuel use is related to exercise intensity
The take home message:
 Fatty acids are a widely used fuel
 Fatty acids are catabolised by boxidation to yield acetyl-CoA
 b-oxidation is mainly regulated by the
delivery of substrate
 Exercise increases the requirement for
ATP
 Different types of exercise utilise
different energy producing pathways