Question : experiment of Electron Transport Chain THX!!!!!!
rainie_yingying at hotmail.com
Wed Apr 23 00:02:19 EST 2003
THX!!! the following is the experiment and questions,
To determine which segments of the electron transport system (ETS) are
responsible for proton pumping and hence for ATP synthesis, some
isolated mitochondria with b-hydroxybutyrate, oxidized cytochrome c,
ADP, Pi, and cyanide had been incubated. (Mitochondria have a
NAD+-dependent dehydrogenase that is capable of oxidizing
b-hydroxybutyrate to b-ketobutyrate.)
l I wonder what the most likely pathway of electron transport in this
Then, was the electron donor in this system b-hydroxybutyrate
(since b-hydroxybutyrate + NAD+ à NADH + b-ketobutyrate)?
l As I see cyanide was the only reagent added to the system that is
not a part of the balanced equation for the reaction. Is the purpose
of adding cyanide to the system was to inhibit cytochrome c oxidase,
and thus blocking all electron transport?
What would the result be if the cyanide had not been added?
l Would the enzymes of the TCA cycle to be inactivated in this assay
l If so is it because of: the electron transport chain is blocked,
the NADHs produced by the TCA cycle will be accumulated and cannot be
regenerated back to NAD+ within the mitochondria matrix. Since some
key steps require NAD+ as coenzymes, the affected enzyme is not
functioning well without the presence of oxidized form of the
l Lastly, why is it important that b-hydroxybutyrate cannot be further
metabolized in this system? Lactate is quite similar in structure to
b-hydroxybutyrate but can be metabolized to pyruvate. What effect
would it have had if the investigators had used lactate as the
oxidizable substrate instead of b-hydroxybutyrate?
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