Review PCr
Facilitated diffusion
Glycolysis (anaerobic
glycolysis, ~10% of available
energy from glucose
molecule)
Hexokinase
• inhibited by high ATP and G6P
• stimulated by high glucose
PFK
•
•
•
•
•
•
ATP (-)
F6P (+)
1,6DP (-)
citrate (-)
ADP (+)
AMP (+)
PK
• F1,6DP activates PK
Glucose Paradox
Tricarboxylic Acid Cycle
(TCA), Citric Acid Cycle,
Kreb’s Cycle
Pyruvate → Acetyl CoA, via
pyruvate dehydrogenase
hub of all aerobic metabolism
Pyr + CoA + NAD → Acetyl
CoA + CO2 + NADH + H
via enzyme pyruvate
dehydrogenase
Glycolysis
• Net ATP = 2 without ETC
• Net ATP with ETC = 12
• Net ATP from one glucose molecule = 36 38
• There are many that have said that the net
is 36 ATP
• The reason for the difference is the
shuttle utilized
• In insects, the shuttle "costs" 2 ATP, so
the net is 36 (glycerol phosphate
shuttle)
• In humans, 38 b/c malate/aspartate
shuttle OXA and pyruvate are moved
into the mitochondria for a cost of 0
• The shuttle moves the pyruvate into the
mitochondria
Review reactions of TCA
GTP + ADP ↔ GDP + ATP
via nucleotide diphosphate kinase
Citrate Synthase
•
•
•
•
•
ATP (-)
NADH + H (-)
succinyl CoA (-)
acyl CoA derivatives of fatty acids (-)
substrate availability
Succinate DH
• another key regulatory enzyme
• this reaction occurs in the mitochondrial
membrane, not the matrix
• SDH is part of the ETC
Third fate of pyruvate: OXA
• via enzyme pyruvate carboxylase
(contains biotin)
• Acetyl CoA (+), need more OXA
• provides OXA, substrates for
gluconeogenesis
Fat catabolism during low
intensity exercise
low intensity = 40-50%
VO2max, 45% VO2max ~60%
HR training zone
Intensity increases to ~5070% there is greater demand
for CHO oxidation as well fat
oxidation
Reference Man = 70 kg, 15%
fat
15% of 70 kg = 10.5 kg, =
10,500 g of fat
kcal/gm = 9
9 X 10,500 = 94,500 kcals!!!
Next, Beta Oxidation…