Question

Describe the proton motive force (PMF, aka ΔΥ). Where is it found? How is it established? What is its purpose? How does it relate to the phenomenon of proton leak, and how does proton leak actually occur? What is meant when we say that proton leak is 'non-ohmic' ? Why do we think that matters during metabolic rate suppression?

Answer 1

Proton motive force is generated in mitochondria and also in chloroplast. IN the mitochondria, ETC is present in inner membrane of mitochondria. During electron transport chain, electrons are carried along the ETC. But protons are pumped out of the mitochondrial matrix in to the outer compartment. This transfer of protons creates proton gradient. The inner membrane of the mitochondria is impermeable to protons. There are ATP synthase complexes which allow the movement fo these protons. The movement fo the protons creates the proton motive force. The protons move from outer compartment to inner compartment through a tunnel present in the ATP synthase complexes.The flow of the movement of protons generates energy. This energy is called proton motive force.

Such a process where particles are moving from the region of their higher concentration to the region of their lower concentration through a semipermeable membrane is called chemi-osmosis.

The energy is used in synthesis of ATP . So the purpose fo proton motive force is the synthesis of ATP which is very essential for survival.

Due to some inhibitor molecules, the inner mitochondrial membrane might become permeable to protons. This will prevent the generation of proton gradient. When there is no proton gradient generated, ATP can't be synthesised. This effects the entire metabolism and functioning of the body. Proton leak can also occur in the inner mitochondrial inner mebrane partially which causes increased metabolic rate to produce ATP. So more proton leak results in more metabolic rate of the organism. Experiments how that certain Uncoupling Proteins UCPs play a role in proton leak.

Changes in proton leak changes the respiratory rate. Less proton leak in a cell, there will be less respiratory rate in cell. The metabolism of a cell is based on the extenct of proton leak.

Metabolic rate suppression is when the body metabolism is reduced. In such a case proton leak will result in much lesser amount of ATP generation than required by the body.

Mitochondrial proton conductance is non-linear or non-ohmic.