What do our cells and hydroelectric power stations have in common?
If you go to Dinorwig, a small village in North West Wales,
you will see an incredible feat of engineering. Below Elidir mountain, 16km of
tunnels1 make up a hydroelectric power station with an approximate
output of 1,728 megawatts2. How is
this electricity generated?
Dinorwig power station is one of only two pumped-storage
hydroelectric power stations in the UK (the other one is in Ffestiniog, also in
North West Wales). But a very similar system exists at all times in the cells
of every single living organism: chemiosmosis.
When we respire, we break down glucose in the presence of
oxygen to release energy, which can then be used to drive processes in our
cells. This actually takes place in a large series of chemical reactions which
occur in the mitochondria (the “batteries” of living cells). In the final step
of this process, electrons are passed through a series of protein complexes,
releasing bursts of energy that can be used to pump hydrogen ions from the
interior of the mitochondria to the space between its two membranes. In this
stage, the ions are being pumped from a lower to a higher concentration
(naturally they would move from higher to lower without the input of energy).
This is analogous to the pumping of water from the lower reservoir to the
higher reservoir, using energy to drive the water against the force of gravity.
The hydrogen ions in what is known as the intermembrane
space now have potential energy in the form of a concentration and charge
gradient. Our cells can make use of this energy: as the ions flow passively
back from the intermembrane space into the interior of the mitochondria, the
energy from their movement is used to produce a molecule called ATP, the energy
currency of our cells.
To me, chemiosmosis is just one illustrator of the fantastic
machinery of our cells and bodies. It never ceases to amaze and dumbfound me
how complex even the most primitive of organisms are, and how evolution by
natural selection has shaped the biological processes that occur within our
cells all the time without us even thinking about them. I hope you find this as
interesting as I do, and if you didn't already know about the chemiosmotic
mechanism, then perhaps you've learnt something new.
I haven’t decided what my next blog post will be about, but
it could be on either eusocial behaviour or the biological significance of
water. If you’re reading this, I would really love feedback and ideas, just so
I know that I’m reaching people! Thanks a lot.
References:
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