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Re: [Phys-l] gasoline

* Oxygen is a product of the light-driven water-oxidation reaction
catalyzed by photosystem II; it is not generated by the fixation
of carbon dioxide. Consequently, the source of oxygen during
photosynthesis is water, not carbon dioxide.

[edit <>]

Further reading of the site I referenced might answer your
question. I'm too lazy to do this for you. [bold is artifact
of copy]

bc, who thinks Tim is on to something, but is going to let someone else verify that.

p.s. cellulose (C6H10O5)n 6*12 vs. 10*1 + 5*16 or 72 vs. 90 [confirming Tim.]

So I may have done it anyway, evidently Tim is correct and other poster are not.

Folkerts, Timothy J wrote:


Just out of curiosity, what is considered the correct answer? I have
limited background in biology, but my thinking is like this.

Plants take in CO2 from the atmosphere and give off O2, so the carbon in
the tree comes from the air.
Wood is mostly cellulose, which is more than half O & H by weight. If
the O & H come from water, isn't this taken up by the roots "from the
soil"? Granted it isn't the soil itself that is collected by the roots
and turned into wood. Still, more than half of the mass would be
collected by the roots from the ground.

Or is the O taken in from the air as well? Perhaps some of the O from
the CO2 is kept and some is released. But then what about the H?
Tim F

-----Original Message-----
[] On Behalf Of John M
Sent: Thursday, August 31, 2006 3:24 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] gasoline

As surprising as the answer to how much CO_2 is produced, the reverse question is just as interesting and could not be answered by most Harvard graduates.

Given a wooden log, where did most of the mass of the log come from.

Most Harvard graduates said the soil.

John M. Clement
Houston, TX

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