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In essence, the Goldman formula expresses the membrane potential as a weighted average of the reversal potentials for the individual ion types, weighted by permeability. (Although the membrane potential changes about 100 mV during an action potential, the concentrations of ions inside and outside the cell do not change significantly.
[1] [2] There is debate as to whether or not this channel is expressed in the cell surface membrane. [3] [4] [5] This major protein of the outer mitochondrial membrane of eukaryotes forms a voltage-dependent anion-selective channel (VDAC) that behaves as a general diffusion pore for small hydrophilic molecules.
Mitochondria present in all cells in the human body require a resting membrane potential of the inner mitochondrial membrane to synthesize adenosine triphosphate (ATP). This membrane polarity is established through a series of proton pumps transporting hydrogen ions into the mitochondrion.
It is an active pump that generates a proton concentration gradient across the inner mitochondrial membrane, because there are more protons outside the matrix than inside. The difference in pH and electric charge (ignoring differences in buffer capacity) creates an electrochemical potential difference that works similar to that of a battery or ...
This membrane potential is ultimately what allows for the mitochondria to generate large quantities of ATP. [ 17 ] Protons being pumped from the mitochondrial matrix into the intermembrane space as the electron transport chain runs, lowering the pH of the intermembrane space.
When Δψ is lost, protons and some molecules are able to flow across the outer mitochondrial membrane uninhibited. [7] [8] Loss of Δψ interferes with the production of adenosine triphosphate (ATP), the cell's main source of energy, because mitochondria must have an electrochemical gradient to provide the driving force for ATP production.
The outer membrane is porous, whereas the inner membrane restricts the movement of all molecules. The two membranes also vary in membrane potential and pH. [3] These factors play a role in the function of mitochondrial membrane transport proteins.
The energy transferred by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport. This generates potential energy in the form of a pH gradient and the resulting electrical potential across this membrane.