Anaerobic and Aerobic
Topics that will be covered…
~Overview of Glycolysis
and description of the
within the muscle and
how does aerobic
metabolism also help
energize our muscles?
~The three main energy
sources for our muscles.
~Ancient metabolic pathway used by the earliest bacteria
~This pathway existed about 1 million years before oxygen
existed on the earths surface.
~Basically, glycolysis is a set of chemical reactions that
produce energy (in the form of ATP) from the sugar glucose.
~In the 10 steps of glycolysis glucose is converted to pyruvate
and the reaction yeilds 2 pyruvate molecules and 2 net ATP
molecules per glucose.
The glycolysis pathway
Now what can be done with
Anaerobic glycolysis is the process by which the normal pathway
of glycolysis is routed to produce lactate. It occurs at times when
energy is required in the absence of oxygen. It is vital for tissues
with high energy requirements, insufficient oxygen supply or
absence of oxidative enzymes.
Glycolysis produces reduced forms of NAD in the energy generation
In an anaerobic environment, lactate dehydrogenase converts pyruvate
to L-lactate and restores NADH to NAD+ which can then be used in
once again in the glycolysis pathway.
The fate of pyruvate
Pyruvate + NAD+ + CoA Acetyl CoA + CO2 + NADH + H+
Using pyruvate in this way (to keep glycolysis running at a paltry
2ATP per glucose) may seem wasteful considering the much larger
amount of ATP generated should it enter the citric acid cycle (as
acetyl CoA). However, glycolysis can run at a very high rate and
thus meet the ATP demands of the cell (at least for a short time) even
though it is a very expensive use of glucose.
But… a continuous buildup of lactic acid could lead to acidosis
So then what do our muscles do
with the lactate produced?
It turns out breakdown of glucose to pyruvate within muscle
cells is not the primary source of ATP synthesis.
ATP is the immediate source of energy for muscle
contraction. Although a muscle fiber contains
only enough ATP to power a few twitches, its
ATP "pool" is replenished as needed. There are
three sources of high-energy phosphate to keep
the ATP pool filled.
•cellular respiration in the mitochondria of
Creatine phosphate and cellular respiration as a
source of ATP for the muscle
The phosphate group in creatine phosphate is attached by a "high-
energy" bond like that in ATP.
Creatine phosphate + ADP ↔ creatine + ATP
of ATP aids in the
glycogen from the
lactic acid that has
built up within the
Biochemistry second edition written by Christopher Mathews and
K.E. Van Holde.