What Is Food Energy?

[zoobyshoe]

I am vaguely aware that the food we eat constitutes a sort of fuel that can be thought of as "calories" for comparative purposes, but I don't really have any idea how the body takes this fuel and harvests energy from it.

A certain amount of the calories we eat have to go to maintaining body temperature but the food obviously isn't combusted in any conventional sense. So, one thing I'm wondering where the heat actually comes from.

The other is how food is turned to muscle contractions that allow us to move ourselves and other things.

[selfAdjoint]

I am vaguely aware that the food we eat constitutes a sort of fuel that can be thought of as "calories" for comparative purposes, but I don't really have any idea how the body takes this fuel and harvests energy from it.

A certain amount of the calories we eat have to go to maintaining body temperature but the food obviously isn't combusted in any conventional sense. So, one thing I'm wondering where the heat actually comes from.

The other is how food is turned to muscle contractions that allow us to move ourselves and other things.


Since nobody more expert has answered this, I'll take a shot. The "burning" is still oxydation, in the sense that an oxygen atom gets tacked onto a molecule, but rather than Avogadro's number of oxygen atoms getting tacked onto different molecules all at once, this biological oxydation happpens at the retail level. If you look up glycolysis on wiki, you will see a series of chemical reactions that break down glucose by shoving oxygen and other groups around from molecule to molecule, and use the energy harvested from this process to force a third phosporus atom (or maybe it's a whole phosphate group) onto adenosine diphosphate molecules, turning them into adenosine triphosphate(ATP). You can look that up too; ATP is the "currency" of the body's systems. These are then sent to the cells via the bloodstream and the cells break them apart as needed to create spurts of chemical energy to do cellular things with. Such as, if it's a muscle cell, contract.

[zoobyshoe]

Thanks, sA. I was thinking no one was going to answer. I'm glad to find out there is a "currency". It's a toehold for sorting out and understanding the other parts better.

I'm still curious about body temperature. Are there dedicated cells for this? The tolerance is pretty tight, and I'm aware that one thing the hypothalamus in the brain does is to regulate body temperature, but I don't know what it controls to do this. Does it communicate with some element of the endocrine system which then instructs "heater" cells to engage in heat creating chemical reactions?

[gravenewworld]

this is what i vaguely remeber from biochem

glucose----> glycolysis---->TCA cycle------>oxidative phosphorylation


oxidative phosphorylation is where most of the ATP you need for energy comes from via NADH and FADH cofactors. ATP energy is released when hydrolysis of the phosphate phosphate bonds occur. The change in energy of the decomposition of ATP to ADP is -12 kcal/mol.

[zoobyshoe]

The change in energy of the decomposition of ATP to ADP is -12 kcal/mol.
Yeah, the wikipedia article suggested by sA had a couple pretty interesting facts on this subject:

The total quantity of ATP in the human body is about 0.1 mole. The energy used by human cells requires the hydrolysis of 200 to 300 moles of ATP daily. This means that each ATP molecule is recycled 2000 to 3000 times during a single day. ATP cannot be stored, hence its consumption must closely follow its synthesis.

http://en.wikipedia.org/wiki/Adenosine_triphosphate

That's alot of recycling.