AP Syllabus focus:
‘Proton flow through ATP synthase drives oxidative phosphorylation; in some cases, decoupling generates heat for endotherms.’
Oxidative phosphorylation is the major ATP-producing process in aerobic respiration, converting energy stored in a proton gradient into chemical energy. This page focuses on ATP synthase-driven ATP formation and how “decoupling” can divert that energy into heat.
Core idea: using a proton gradient to make ATP
Oxidative phosphorylation occurs on the inner mitochondrial membrane and depends on a pre-existing electrochemical proton gradient (built by upstream electron transport).
Practice Questions
FAQ
Sympathetic signalling can increase free fatty acids that activate UCP activity.
Gene expression of UCPs can also rise with cold exposure, increasing thermogenic capacity.
With a reduced proton gradient, mitochondria may oxidise more fuel to try to rebuild it.
This can drive higher respiratory activity even though ATP output falls.
Excessive proton leak can cause ATP shortage, impairing ion pumps and biosynthesis.
In extreme cases, loss of energy conservation can contribute to cell dysfunction.
They commonly compare oxygen consumption rates with and without ADP or with uncouplers.
The ratio of respiration linked to ATP synthesis versus proton leak indicates coupling efficiency.
Some chemicals shuttle protons across membranes, collapsing the gradient.
They can cause dangerous overheating and ATP depletion, so therapeutic use is tightly limited.
