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

A simple method would me to express a fluorescent protein in the cell that specifically localizes to mitochondria. mito-dsRed is a Red Fluorescent Protein which has that property; it can be expressed from a plasmid.

Using fluorescent microscopy and image analysis, you would be able to measure the geometric properties of the mitochondria. This can be done at a single cell level too (using confocal microscope) and non-destructively. Volume can be measured by what is known as Z-stacking— an automated technique by which the microscope takes several 2D snaps at different planes and stacks them to construct a 3D image.

You can implement this in live cells too; this method is called live cell imaging.