Living things maintain their order by taking in fuel to run chemical reactions. the fuels are protein, fat & carbohydrate. in common parlance, we burn these fuels to generate ATP that runs chemical reactions, to make everything in our bodies, repair everything, move & think. /1
Fully oxidized, the carbon in the fuels is exhaled as CO2. /2
The energy in the fuels consists of high energy electrons, whose energy is derived from the sun (that lesson for another day). /3
The energy in the fuels consists of high energy electrons, whose energy is derived from the sun (that lesson for another day). /3
The difference between living things & locomotive machines that imparts the ability to build ourselves is that we have NAD coenzymes that capture the energy associated with fuel oxidation in a nearly lossless manner. /4
When fuels are burned in a steam engine, the engine is designed to capture as much of the heat as possible to do work. /5
But when fuels are burned in cells, the high energy electrons are captured on NAD+, forming NADH, which can hand off electrons to other intermediate compounds that sustain chemical reactions in ways that minimize the production of heat. /6
Less heat generated means more of the energy in the food we eat is available to do chemistry that makes us & keeps us running. /7
One of the coolest things our cells do is simultaneously flow electrons from food to NAD+ to then form NADPH to build DNA, RNA & lipids. The reactions are literally cool to the touch: they can happen in organisms that live in the refrigerator. /8
Take home message: living things evolved cool chemistry that directs the flow of high energy electrons by capturing them on NAD coenzymes to build and repair every part of every living thing. /end
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