Tag Archives: endosymbiosis

Chemiosmosis and DNP; endosymbiosis

I am indebted to one of my colleagues for the following idea – I think it’s brilliant, many of you may already use it, or something similar, but it was new to me and sent me rushing to e-bay to purchase a World War 1 brass shell casing. Not got one in your department? You really should! I would put it up there with our Archaeopteryx fossil cast, our horse front leg bones and our giant brine shrimp tank as being an infallible source of student excitement and curiosity.

Year 13 again, I’m afraid. And as the attached powerpoint shows, it’s the story of the women working in munitions factories in WW1, and the fact that they showed dramatic weight loss (they also turned yellow and were called “canaries”, but that’s another tale). Why? Why? It’s a great example of how to open a lesson with a mystery – it grabs their attention, their imagination, and they get excited because they want to know the answer, they know they’re going to find out the answer, and, if you do it right, they get to work out the answer, which makes it even more satisfying.

So, one of the components of the explosives put into the shells was DNP, or di-nitrophenol. These days, it’s better known as an illegal weight loss pill, and there’s the tragic story of the young Leeds University student who died after taking it. But in the munitions factories it was just a weird and unexplained mystery. What does it do? It acts as a proton channel in the inner mitochondrial membrane. Now why would that make you lose weight? Their ability to explain this is a great test of their understanding of oxidative phosphorylation. You can also link it to brown fat, small babies, and hibernation. So, buy a shell! You can get them for around £10 to £15 on E-bay, and if nothing else, you get the satisfaction of explaining to the school accountant why you’re purchasing WW1 munitions…

…I’m also looking forward to being challenged over my purchase of a bottle of whisky for Year 7 Science. They’ve been studying separation techniques and I set them the challenge of working out how they would separate water and alcohol. As a consolation for not being allowed to actually do it, I’m taking them up to the school kitchen on Friday to teach them how to flambé bananas, which will be deliciously fun, but will also dramatically demonstrate why we don’t distil alcohol in the lab! Flambé bananas, I should add, are the signature dish of Bill, along with fluffy pancakes and slow barbecued lamb.

I’m afraid my idea for getting students to work out the Krebs Cycle flopped rather badly. That’ll teach me to never share an idea before I’ve tested it! Not only did it not work, they got terribly confused about everything and I had to wade in and do some heavy duty lifting to rescue things. It’s been modified now, and I’ll try it again next year, but much more carefully…

Nick and I are currently both trying to get a working model of chemiosmosis going, like the one Brian Cox showed on his programme I can’t remember the name of. Acid and water separated by some visking tubing with a couple of electrodes – a battery, basically – should be able to power a small motor. Mine didn’t even power a small LED and we ended up with about a litre of 0.1M HCl on the floor. Ahem. The origin of life needs a little more work…

One thing that does work is Endosymbiosis with Year 12. After a little background on the history of life and that crucial moment when complicated cells first appeared, I introduce them to Lynn Margulis (see attached sheet) and her idea. They then have to make some predictions about mitochondria based on this suggestion – and then find out if these predictions are true. It can take them a while to figure out what I mean by “prediction” but they will all suggest the presence of plasmids, ribosomes, binary fission, size/shape and susceptibility to antibiotics. The best of them will even predict that mitochondria should have two membranes, which is always a champagne moment.

Have a great week.


Munitions and DNP

TEM bacteria vis plant cells

Lynn Margulis and Endosymbiosis