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Comment by fratlas | Hacker News Reader

Dumb question, but would it be possible to have a nuclear-powered object in your body producing energy for your body to use?

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Keeping nuclear material (safely) in your body is the easy part, the hard part is converting that energy into something your body can use. The issue is, our (badly designed) meat-hardware runs on glucose instead of heat or electricity, and there's no easy (or any way that I know of really, but then I'm not a scientist) to convert heat/electricity into glucose.

I went to a lecture recently by a researcher who is investigating the mechanisms of photosynthesis. The chlorophyll uses the energy from the photon to pump an electron, which (after a long and poorly-understood chain of reactions, which is what he was studying) creates an energy gradient which powers ATP synthase to produce ATP. Presumably if we understood and could recreate this reaction, we could create the electrochemical gradient directly, and then use it to power the ATP synthase and subsequent glucose-production mechanisms.

What kinda gaps in our understanding do we have that limit the reserach for this idea. I know I've seen some news or buzz about creating electricity with "green solar panals": basically using photosynthesis instead of photovoltaic cells. Maybe you can figure out a way to manage the gradient in photosynthesis by trying to see which proteins and complexes and pathways we can fiddle with to regulate it the way we want. But still, even to get to that point we need to map out and understand a lot about the reaction and system before we can begin to probe and see what we can do.

> Presumably if we understood and could recreate this reaction, we could create the electrochemical gradient directly

We don't need to reproduce the reaction, we know how to create a potential (in Volt) gradient between two faces of a membrane : you just need electrodes for that purpose.

Biochemists at Caltech were studying photosynthesis back in the 70s, with an eye towards artificially replicating the process.

I see not much progress has been made.

This is a paper from two years ago but it shows that progress is still being made in this field. http://science.sciencemag.org/content/352/6290/1210

That's true but isn't 80% of our energy usage used to heat and regulate our body temp? I was wondering if we would then need less "food" for daily calories...

Where I live there is a rather large temperature change between summer and winter (usually 60 K, sometimes higher), and during the summer I definitely feel the need to eat less calories. However this may just be an emotional response rather than anything biological.

Ambient temperature definitely affects calorie consumption. No doubt about it. Body burns more calories keeping organs at 37C if the exterior is 10C, compared to 40C.

Don't you start to get overheating phenomena at 40C?

If you count "sweating", then sure.

Isn't heat essentially a by-product of muscles "burning" the glucose? I'm not sure we actually need more heat besides what's already being generated as a by-product.

No, you can actually induce greater caloric expenditure by lowering the ambient temperature (within reason), if I’m not misremembering.

This is, after all, the distinguishing characteristic of mammals. Reptiles have no shortage of muscle mass (just look at aligators or crocs!) but still can’t raise their body temperature to compensate for cooler weather or environments.

You're correct, mammals have systems to convert energy in to heat without movement and regulate this very effectively.

This isn't a distinguishing characteristic of mammals though - all birds and a few fish can regulate their body temperature. The distinguishing feature of mammals is the mammary gland - the production of milk for young.

It's possible that a factor in the raised temperature is that it deters fungal infections.

https://www.newscientist.com/article/mg21228411-700-killer-f...

See https://en.wikipedia.org/wiki/Brown_adipose_tissue

You need more if you're cold enough!

Go out in frigid weather with a T-shirt on. You'll soon shiver - your body is recruiting muscles to generate heat. But also, your "brown fat" cells will start pumping out heat as well.

Liver also speeds up metabolism creating yet more heat.

You could "just" make a nuclear liver that snapped metabolic byproducts back together.

I guess you might not directly target the production of glucose, but there should be some places in the metabolism where food energy could be replaced with energy from the plutonium.

The ability to metabolize radiation does exist (https://en.wikipedia.org/wiki/Radiotrophic_fungus) so we might be able to modify our genes such that our bodies can use this energy directly.

This might interest you: https://en.wikipedia.org/wiki/Radiotrophic_fungus

I look forward to the day nuclear powered sustenance becomes a fad diet, and accidentally creating immortal zombies whose minds have expired before their bodies.

I don’t think that’s dumb, and the answer is... sort of. The easiest way to make it work would be to have the device somehow help to heat and cool you internally, which would save you energy. You might be able to use the power to produce ATP or some other metabolic necessity, and deliver it where needed.

The problem is that you’d need a respectable amount of radioactive material in you, waaaaay more than you’d need for a pacemaker. It would probably make more sense just to keep some glucose syrup and a hand warmer around.

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