Re: If cells process oxygen for energy, why is food energy needed?

Marino -

This is a very challenging question. 

You are right, cells need oxygen to get energy. But they also need food. 
Food is really where the energy comes from - we break our food down into 
simpler pieces, and release energy. 

If there is no oxygen, we don't really get much energy - but if we have 
both food and oxygen, we can get a lot of energy from our food. There is a 
special name for this, it's called aerobic metabolism. 

Organisms which can live without oxygen are called anaerobic.

So, you get the engery from your food, but oxygen helps you get the most 
energy possible.

An easy way to illustrate this is to try and run across a field with your 
mouth closed - you can't hold your breath and run - you need oxygen. You 
already know that you need food - this means you really need both food and 
oxygen.

I hope this answers your question - keep asking good questions!

Tod Companion, Ph.D.
University of Alabama at Birmingham
Biochemistry and Molecular Genetics