In the presence of oxygen and in the absence of ADP,what occurs if the uncoupler 2,4-dinitrophenol is added to a suspension of normal mitochondria five minutes after an oxidizable substrate has been added?
A)The substrate will be oxidized until the addition of the 2,4-dinitrophenol,which blocks further oxidation.
B)There is no effect;oxidation of the substrate continues at the same rate before and after the addition of 2,4-dinitrophenol.
C)The substrate cannot be oxidized either with or without 2,4-dinitrophenol unless ADP is also present.
D)Oxidation of the substrate does not occur until the 2,4-dinitrophenol is added.Afterward,oxidation proceeds rapidly until all of the substrate is consumed.

Question

Quizplus · Accepted Answer

2,4-Dinitrophenol acts as an uncoupler by dissipating the proton gradient across the mitochondrial membrane, which normally drives ATP synthesis. Without ADP, the electron transport chain is inhibited due to a lack of ADP to phosphorylate to ATP, causing a backup of electrons and slowing substrate oxidation. Adding 2,4-dinitrophenol removes this inhibition by uncoupling ATP synthesis from electron transport, allowing oxidation to proceed rapidly.

In the Presence of Oxygen and in the Absence of ADP,what