Tuning the Cell’s Mitochondria

Tuning the Cell’s Mitochondria

In a previous post ‘Mitochondria the beating heart of the cell’ I described mitochondria as oscillators. The reasoning behind this was that mitochondria behave as capacitors in an electronics sense in which they are charged by electrons supplied from substrates as they ‘descend’ in redox potential through the so called respiratory chain of redox enzymes.

In turn they are discharged by the collapse ( partial ) of the electro-potential across their inner membrane, the energy of which is used to drive the synthesis of molecules such as ATP or to reduce nicotinamides or flavins ( NAD, FAD).

All the above is known to all students of biochemistry, many of whom are reluctant physical chemists and for sure not electrochemists or electronics geeks. When these ideas were first mooted and referred to as the Mitchell Hypothesis in the late 1960s the ‘wet bio-chemists’ reacted badly and it took many years for electro-mitochondria to gain a foothold. Indeed it was absent completely from A level text books well into the 1980s.

This was understandable as biology-organic chemistry was forced to encounter topics such as redox and Gibbs free energy. Concepts they did not meet normally …  and they certainly were not going into the territory of distinctions between enthalpy, entropy and the Nernst equation. A kind of truce settled after a while and the stuff got taught and then ignored.

However what seemed to be the case is that the silo that is science managed to keep well clear of interference from the rapidly developing world of micro-electronics. The circuit folk made little contribution to the bio-energetics world which had refined its physical chemistry and now well understood the movement of electrons up and down energetic pathways.

I have always been an advocate of the next steps and to reiterate a previous blog: 

Since  mitochondria hold charge and this charge can be used on demand they are acting like simple capacitors. And as capacitors:

1. They have a measurable capacitance which will vary according to  the dielectric properties of their membranes, the medium that surrounds them and their surface area.
2. They will have a ‘smoothing effect’ on chemical reactions that require electrons ( ie reducing reactions ( anabolic-biosynthetic, as opposed to oxidations which provide electrons) by providing a reservoir of charge above the threshold potential required for synthesis.
3. They will pulse or oscillate with defined frequencies if there is a time discrepancy between the rate of charge and discharge. This is likely because discharge occurs in discrete free energy ‘lumps’ larger than the supply-side electron donation from substrates.

When cells senesce mitochondria enlarge and have fewer inner-folds of membrane ( cristae). In other words they have a lower capacitance. This can be explained as follows:

A reduction in surface area means that it takes less charge to reach its working potential ( voltage). If, as seems the case, the dielectric of the membrane has decreased with age, that is in  biochemical terms it is ‘leaky’ with regard to ion porosity, then a reduced surface area allows, to use a simile, ‘the bath can be filled faster than it empties’.

For a long time I could not work out why the mitochondrion should enlarge also. I now think it is to maximise the ratio of ‘electron supplying’ matrix-located  reactions ( TCA mostly ) ) to the surface to be supplied.

The logical consequence of this response which seems adaptive to membrane integrity is that the mitochondrion will carry on ‘working’ but with reduced reserves. In the parlance the critical membrane depolarisation threshold is ever closer.

This concords with everyday observations of senescent mammals. They can’t keep   going, they run out of puff!

Finally, something of an intrigue for me is the oscillation of the charge that must occur. Oscillators have resonant frequencies, tuned circuits have resonance Resonance allows for transfer of energy and resonance energy transfer is well know in the photosynthetic electrochemical processes. 

Do mitochondria react to external electromagnetic resonant frequencies and if so what? Are cells ‘tuned’ systems? I won’t find out that’s for sure but every New Age ‘energy-field’ buff will just love it