why we breathe oxygen and not something like carbon dioxide or nitrogen?
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Oxygen is a great acceptor of electrons. So much so that it is used in a process called chemiosmosis which is the final step of extracting energy from glucose, out bodies’ main fuel source.
This extraction can be broken down into a number of steps: Glycolysis, where glucose is chopped into two molecules called pyruvate. These are then converted into molecules called acetyl-coenzyme-A, which goes into a series of steps known as the Citric Acid (or Kreb’s) Cycle. After this, all of the carbon in glucose has been turned into CO2, which we exhale as a waste product.
These steps don’t make very much of the cell’s “energy currency”, a molecule called ATP, but a lot of the energy from glucose gets captured in molecules called NADH and FADH2. These can give up that energy in the cell’s mitochondria during chemiosmosis, which drives a process that makes a huge amount of ATP.
The final step involves the electrons carrying the energy from these molecules joining with hydrogen ions and oxygen atoms to form water, respiration’s other waste product.
Without oxygen, this process can’t happen, energy production is way less efficient and complex animal life wouldn’t have been able to develop.
At the very basic level we are machines that consumes sugar for energy. Sugar is made of carbon, hydrogen and oxygen. We convert the sugar into H2O(water) and CO2 to extract the energy in sugar. But there’s not enough oxygen in sugar to complete the reaction. Therefore we breathe in oxygen to facilitate this reaction.
We DO breathe nitrogen, it’s 70% of the air, so it definitely gets in our lungs. Furthermore, it also gets in our blood stream, too!
We just don’t use it like we use oxygen…
We breath air, which is 78% nitrogen, 21% oxygen and 1% other gases, such as carbon dioxide.
Oxidation.
Cells need oxygen so that it can react with sugar, which in turn makes energy available for that cell. Oxidation only works with oxygen, so things like nitrogen aren‘t useable.
Carbondioxide can be used for oxidation, but those reactions are more forced, so to speak.
It simply happens to be that oxygen is abundant and can be used as an easy way to release energy. Because it has worked life kept using it.
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