Scratch

Well, that's not very polite.

There are two chemical reactions that convert glucose into an form of energy that our bodies can use.

One of these does not require oxygen, but is not very efficient.

The other requires oxygen, and is much more efficient.

As a complex, multi-cellular organism we need the more efficient form of reaction (Known as the Citric Acid Cycle) in order to provide enough energy for our bodies to survive.  Hence we need to breath oxygen.

The two oxygen atoms held within a carbon dioxide molecule would require more energy to break free from the carbon molecule than would be gained from their subsequent reaction, so we cannot breath carbon Dioxide.  The same is true of the oxygen molecule attached to the two hydrogen molecules in water...

We do breathe in carbon and oxygen,But mostly nitrogen(i think we breathe mostly of some gas but not oxygen).

jasb wrote:

Paddle2See wrote:

Well, that's not very polite.

Why, maybe the guy that asks is in the room full of carbon dixide and he can't breath. He wil die in a few seconds so he is unpolite.    I think it's a good explenation.

I hadn't considered that scenario.  In an emergency, there isn't always time for good manners.  That's probably it!

Not everybody knows *why*, though 

If you want to get really technical, one could say it is because the mitochondrial nuclei of our cells are evolved of aerobic bacteria that required oxygen, but that would probably upset somebody 

DotsandStripes wrote:

You'll die.

Unless your a tree.

Even if you are a tree.

Plants require oxygen for respiration, just like humans.

A plant in a room full of CO2 would die, unless it was able to photosynthesise CO2 into oxygen faster than was using that oxygen up.

As that depends on the amount of light available, plants are quite capable of suffocating.

well, over millions of years animals (excluding fish) breath air... exhaling carbon dioxide and plants absorb carbon dioxide exhaling oxygen!

Mayhem wrote:

registeel wrote:

well, over millions of years animals (excluding fish) breath air... exhaling carbon dioxide and plants absorb carbon dioxide exhaling oxygen!

Plants produce oxygen as a by-product of their method of feeding, gettign the energy to do this from sunlight.  This is not exhaling.  Plants also breathe, and in doing so beathe in oxygen and exhale carbon dioxide.

A carbon dioxide detector left in a wheatfield for a week will record a steady decrease of CO2 during the day, but an *increase* during the night.

True, yet over a long period of time there will be a steady decrease in CO2, and a increase of oxygen, thus global warming can be stoped if we have more trees, but humans' need for wood is too great and therefore the tree population is decreasing at an alarming rate!

Mayhem wrote:
There are two chemical reactions that convert glucose into an form of energy that our bodies can use.

One of these does not require oxygen, but is not very efficient.

The other requires oxygen, and is much more efficient.

As a complex, multi-cellular organism we need the more efficient form of reaction (Known as the Citric Acid Cycle) in order to provide enough energy for our bodies to survive.  Hence we need to breath oxygen.

The two oxygen atoms held within a carbon dioxide molecule would require more energy to break free from the carbon molecule than would be gained from their subsequent reaction, so we cannot breath carbon Dioxide.  The same is true of the oxygen molecule attached to the two hydrogen molecules in water...

You know whats scary, i actually managed to follow that 

Last edited by yambanshee (2008-10-31 06:29:15)