How are the physiological properties of mitochondria measured?

Question

this is my first question on BiologySE. I am a Physics and Mathematics student currently doing a project on cell growth simulation. I am doing literature survey and I have a question about cellular biology experimental methods.I understand that the membrane potential is a measure of mitochondrial functionality (higher potential means more efficient electron transport chain). Additionally, the mitochondrial volume is also an indicator of mitochondrial efficiency (higher volume, higher area, more places to do electron transport).I would like to have some points elucidated.In particular, can these mitochondrial membrane potential and volume...- be measured for a single cell, or only in a population?- be measured non-destructively, leaving the cell alive?- be measured simultaneously, or experiments measuring one necessarily make the other unavailable?I am thinking mostly of *in vitro* experiments of course.

Answer 1

Yes, mitochondrial volume (or abundance) and membrane potential are both effective measures of mitochondrial functionality/health and are best measured in vitro fluorometrically with dyes. Depending upon the dye/stain for each application, each dye with their own excitement and emission spectra, they can be used simultaneously depending upon the instrument or technique that is used to measure their fluorescence intensity.

Mitochondria can be isolated from cells or whole tissue, but there is debate surrounding the physiological relevance of mitochondrial function when isolated from cells and cellular influences. Furthermore, cells can either be fixed (or "frozen", using 4% PFA which kills them but gives you a snapshot of cellular function/characteristics) or left alive prior to staining. Membrane potential dyes/stains are best used in living cells, while there are dyes that measure mito abundance/volume in cells that are fixed, living, or both.

The most common ways to measure the fluorescence of these dyes/stains, with increasing fluorescence intensity indicative of more mito and/or higher membrane potential, are with the use of a plate reader, flow cytometry, or confocal/high-resolution imaging.