Life on Earth has a nearly unlimited source of energy: sunlight. The light reactions of photosynthesis transduce sunlight energy (absorbed by beautiful green chlorophyll) into electricity. This would be plenty of energy for any life form. But here is the problem: as soon as the sun sets, or even becomes dim, the organism would have to go into suspended animation. The solution to this problem: store the light and electrical energy in a chemical form. Photosynthesis in chloroplasts puts sunlight energy into sugar, which can be stored and used whenever needed.
Cellular respiration in mitochondria releases chemical energy from sugar in lots of little steps, and makes it available for the cell’s chemical reactions. It does so quietly and invisibly, with an almost 50 percent efficiency. This is much better than even the most fuel-efficient vehicles.
It is easy to overlook just how much energy there is in a teaspoon of sugar. In order to appreciate it, you can release the energy all at once. It produces a very dramatic fizzle. It is not a bomb, but still impressive. It must be done in a fume hood or outside.
- Grind up the sugar. Do not use powdered sugar, since it is not just sugar ground into a powder.
- Grind up some potassium chlorate. This provides oxygen, but no energy, to the reaction.
- Mix the two powders in a plastic weigh boat or other disposable, non-flammable container.
- Pour in a little concentrated sulfuric acid.
- Then get out of the way.
The resulting reaction is zero percent efficient. All of the energy comes from the sugar, none from the oxidizing agent or the acid. And it all goes into light, heat, and noise.
I made a Darwin video that shows the process. Enjoy!
It is this huge amount of efficiently-stored energy that makes life possible.