How does membrane potential vary between intraceullar membranes and the cellular membrane?

Question

Question

Does each type of membrane have a different membrane potential? I'm especially interested in answers that can cite academic papers that have attempted to measure membrane potentials.

Discussion

I've asked about the composition of membranes before , and although I recieved some information, I didn't get all the information I was after. This isn't a problem with our community but rather with the field at large: the popular thinking is membranes are membranes are membranes (mostly due to the difficulties in studying membrane biophysics experimentally).

This is how wikipedia defines membrane potential:

Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. - Wikipedia

This isn't strictly true. Intracellular membranes also have membrane potentials as one can imagine, and there is some unverified information regarding compartmental pH values. This is why I am interested to find out if there have been studies attempting to quantify this across the cell membrane, and across different subcellular membranes.

Answer 1

Yes, various intracellular membranes do have potential differences, but as you can imagine they are more difficult to measure experimentally, so in general data on this is scarce.

Summary

• Mitochondrial membrane: 150mV-180mV with negativity on the matrix side. Seth et al 2011
• Endoplasmic reticulum membrane: 75-95mV with negativity in the ER. Qin et al 2011, Worley et al 1994
• Golgi: No notable membrane potential. Schapiro & Grinstein 2000
• Lysosomal: 20mV with more negativity on the cytosolic side. Koivusalo et al 2011

Discussion

The mitochondrial membrane potential is probably the best studied case. This is the potential difference over the inner mitochondrial membrane, between the mitochondrial matrix and the intermembrane space; it is about 150mV (more negative on the matrix side). There is also a potential difference between the mitochondrial cristae (folds of the inner membrane) and the matrix which is used to drive ATP synthesis; it is probably larger than 150mV, but this is still poorly understood I think. The outer membrane is permeable (has pores) so there should be no potential difference between the intermembrane space and the cytosol.

For the endoplasmic reticulum (ER), there is little data available I think, but there are some estimates based on measurements of ion transport, which gives a value of about 75 to 95 mV (more negative inside the ER). Probably this depends a lot on the situation, as the ER is involved in regulating ion homeostasis (notably Ca2+).

For the Golgi apparatus, this study found that no potential difference vs. the cytosol, based on the movements on H+ and counterions.

Lysosomal membrane potential has been measured directly, giving values of about 20mV (more positive inside).

For the nucleus I don't know of any data, but I would assume there is no potential difference here, given that the nuclear membrane has large pores.