Unformatted text preview: rylation on the inner membrane of
mitochondria to produce ATP
c) After running for a while, the man felt exhausted and he had problems catching
his breath. How was glucose metabolized under this condition when oxygen
supply was severely limited? NO need for names of enzymes and chemical
Glucose is metabolized to pyruvate via glycolysis generating ATP and
NADH. When oxygen supply is limited, mitochondrial citric acid cycle
and oxidative phosphorylation cannot occur. Pyruvate has to be reduced
to lactate (lactic acid) so that NADH can be reoxidized to NAD+ in support
of continuous glucose metabolism via glycolysis (NAD+ is needed in 5 glycolysis). Therefore, when oxygen supply is limited, glycolysis is the only
process to produce small amounts of ATP and lactate is accumulated as an
d) The man finally reached safety when he felt fatigue in his muscles. Now he
could rest and recover from the strenuous running. What happened to his
muscle and liver cells at this stage? Your answer should include 1) names of
pathways involved and 2) cellular locations for each pathway. However, NO
need for names of enzymes and chemical structures.
1) Lactate accumulated in the muscle is secreted to blood and eventually
picked up by liver cells.
2) Liver cells convert lactate to glucose via gluconeogenesis (in cytosol).
3) The regenerated glucose can be sent to muscle for future use.
4) The whole cycle between muscle (glucose lactate) and liver (lactate glucose) is called Cori cycle.
e) Now that the shocking experience to this man is over and the epinephrine level
starts to decline, how does his body turn off the signaling transduction pathway
that has been activated by epinephrine?
1. Activated 7TM receptor can be turned off by interacting with
2. Heterotrimeric G-protein cycles from “on” state (α -subunit with
GTP) to “off” state (GTP is hydrolyzed to give GDP).
3. cAMP can be hydrolyzed (destroyed) by phosphodiesterase.
4. Protein kinase...
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