Please answer question b
In normal mitochondria the rate of electron transfer is tightly coupled to the demand for ATP.
When the rate of use of ATP is relatively low, the rate of electron transfer is low. When demand
for ATP increases electron-transfer rate increase. Under these conditions of tight coupling, the
number of ATP molecules produced per atom of oxygen consumed when NADH is the electron
dono - the PIO ratio is about 2.5. 0 NO, NO, 2,4 dinitrophenol (cytoplasm) a) Illustrate above
then summarize below how 2,4-dinitrophenol works with the structure shown and what you
know of membrane structure. (10 points) b) The uncoupler 2,4-dinitrophenol was once
prescribed as a weight-reducing drug. How could this agent, in principle, serve as a weight-
reducing aid? Include what happens to the P/O ratio in your explanation for additional credit. (5
points) c) Uncoupling agents are no longer prescribed, because some deaths occurred following
their use. Why might the ingestion of uncouplers lead to death? (5 points)
Solution
As per Student request Answer B As follows:
In the people seeking to lose weight DNP was used as a drug. Uncoupling agent uncouple
oxidation from phosphorylation. Electron transport has been continued, but ATP synthesis stops.
Most common uncoupling agent is 2,4 dinitrophenol(DNP). DNP is a weak acid that is soluble in
lipid by layer both in their protonated neutral forms and in their anionic states. DNP in anionic
state pick up protons in the inter mitochondrial space and diffuse readily across mitochondrial
membranes. The protonated form will be entered into the matrix from inter mitochondrial space,
they can release a proton, thus dissipating the proton gradient and thus inhibits ATP synthesis.
However, this is now discontinued, as it produces hyperthermia and other side effects. In fact,
food and Drug Administration has banned the use of DNP.