Structure of Pyruvate
H Glucose Catabolism 2
• Homeolactic fermentation
• Alcoholic fermentation
• Metabolism of hexoses other than glucose
• Pentose-Phosphate pathway
One glucose molecule = 2 Pyruvate molecules! H Glucose Catabolism 2
Once pyruvate is metabolized, it has 3 fates based on
the availability of oxygen
(1)Aerobic conditions: Completely oxidized via citric
acid cycle, results in CO 2nd H O.2
(2)Anaerobic conditions in muscle: reduced to
(3)Aerobic conditions in yeast: Forms ethanol +
Homolactic Fermentation: Occurs in the muscle, particularly during vigorous activity
when ATP demand is high and [O ] is 2ow.
•Glucose + 2 ADP + 2 Pi −> 2 lactate + 2 ATP + 2 H O + 22H +
•Muscle fatigue and soreness is not caused by lactate, but rather by low pH. Muscle
can work long if the pH remains consistent. H Glucose Catabolism 2
Anaerobic Glycolysis: Low efﬁciency but fast. The rate of ATP production by
anaerobic glycolysis can be 100x faster than that of oxidative phosphorylation.
★When muscles work hard, they rapidly consume ATP and regenerate it almost entirely
via anaerobic glycolysis
★ Lactate is not further oxidized --> dead end in the pathway.
Glucose --> 2 lactate + 2H Δ"G = - 196 kJ/mol
However, energy reserve is not wasted. Lactate has two fates:
(1) Carried by blood to liver and new glucose is synthesized
(2) Converted to pyruvate in the muscle
Location Liver Muscle
Final Product Glucose Pyruvate
Slow twitch muscle ﬁbers: Obtain energy
primarily from oxidative phosphorylation. They
are enriched with mitochondria and appear dark.
•Long distance runners are rich in slow twitch
Fast-twitch muscle ﬁbers: Obtain energy via
anaerobic glycolysis and appear light.
•Sprinters are rich in fast twitch ﬁbers
Alcoholic Fermentation: Occurs in yeast and
produces ethanol <333333