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Review Beta Oxidation
Protein Metabolism
20 aa’s that combine in unique
arrangements to form
individual proteins
Amino Acids
 Amino radical (NH2)
 Carboxyl group (COOH)
 The side chain (carbon, hydrogen,
sometimes sulfur or nitrogen) is what gives it
specific characteristics
 10 aa’s are essential, cannot be synthesized
in the body
All aa’s become part of the
amino acid pool: three
compartments
 blood
 liver
 skeletal muscle
aa’s in the compartments are
in equilibrium; change one,
change all, blood is the
communicator
 if one compartment is low, can replenish
from another: glucose-alanine cycle
aa’s brought to liver,
converted to glucose
(gluconeogenesis) and
released in blood for delivery
to working muscle
aa’s in muscle are converted
to alanine, carried to liver,
where amino radical is
removed (deamination)
carbon skeleton is converted
to glucose
After 4 hours of continuous
exercise, liver’s output of
alanine-derived glucose
accounts for 45% of total
hepatic glucose
As intensity of exercise
increases; so does alanine
release from exercising
muscles (7X)
Energy derived from glucosealanine cycle can account for
10-15% of the total energy
requirement
Amino acid metabolism can be
divided as
 disposal of the alpha-amino group (via
alpha-ketogluterate to glutamate to
ammonia to urea)
 carbon skeletons are converted to
intermediates of metabolism
If energy state is high: convert
to acetyl-CoA and stored as
fat
If energy state is low:
catabolized to support
demand (exercise) for energy
Alanine, via pyruvate, yields
15 ATP