|MadSci Network: Biochemistry|
Glucose is a complex molecule, and such molecules contain a lot of latent, or unutilized, energy. Cells try to break down complex molecules into simpler molecules, and so release the energy for the cell to use. I have gone into detail as to how cellular respiration works in answer to a previous question, and you might want to check that out (853102598.Cb) for parts of the explanation that aren't in this answer.
Basically, a molecular derived from glucose, pyruvate, gets taken up into cellullar organelles called mitochondria. There, pyruvate gets converted into another molecule (acetyl CoA) before entering a series of enzyme steps called the TCA cycle, in which, amongst other things, high-energy electrons get released from it.
The energy of these electrons gets used to convert adenine dinucleotide (ADP) into adenine trinucleotide (ATP). (ATP is more complex than ADP and so it takes energy for this conversion to occur.) ATP is like an energy store that can be moved throughout a cell to where its needed. There, it gets broken down to ADP and the spare energy gets released.
So glucose, or other complex molecules including fats, serve as an energy source which cells convert in mitochondria into a more easily transportable form, ATP. From this we get the energy which cells use for many purposes including growth, movement, division etc etc.
Hope this helps!
Try the links in the MadSci Library for more information on Biochemistry.
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