Posted: Feb 06, 2017 5:40 pm
Thanks for your reply Itsdemtitans! Call me slow but let me try to digest that.
Let me start with something I do understand (a bit; I used to be a biochemist in a previous life) which is an interesting thing to know and perhaps relevant for the discussion. Scientists can distinguish sugar from sugar cane and from sugar beets, even though it is chemically 100% the same. Interestingly, the isotopic carbon ratio differs. There is a group of plants that catch CO2 using a so-called C3 mechanism (the relevant molecule has 3 carbon atoms), while another group uses a different route, the C4 mechanism (you guessed it; the relevant molecule has 4 carbon atoms). As it happens, the enzymes involved in each group have a slightly different preference for the CO2 involved (the catalytic cavity is so well adapted that the minute difference in bond length has a tiny but measurable effect; or something).
Now, back to what you tried to explain to me. AFAIK the amount of carbon in the atmosphere is minute compared to the amount available differently. I can image that there is some kind of preference of one type over the other. So, in the atmosphere (but nowhere else) one type builds up by a tiny bit. If there is a release of CO2 (say, lots of decay), it is mostly the other type that is released, so we do get a change. OK. If it is locked away from the cycle (e.g. frozen in limestone), then it no longer plays a role and we have a relatively higher ratio. Got it, I think!
However, I can't help thinking that different (climate) situations favor different groups of plants, and that they play a role here too. AFAIK sugar cane is a C4 plant and well, as you know, it favors high temperatures. Let's not rely one my memory (learned this stuff 30 years ago) and see what Google turns up. And there it is:
https://en.wikipedia.org/wiki/C4_carbon_fixation
Yes, can't remember new stuff but can recall old stuff. I"m officially old now! Wait, I digress.
So, I posit that there is a correlation between the graph that you showed and the temperature in geological time (which hopefully could be deduced through other manners). Can you expand on that?
Bert
Let me start with something I do understand (a bit; I used to be a biochemist in a previous life) which is an interesting thing to know and perhaps relevant for the discussion. Scientists can distinguish sugar from sugar cane and from sugar beets, even though it is chemically 100% the same. Interestingly, the isotopic carbon ratio differs. There is a group of plants that catch CO2 using a so-called C3 mechanism (the relevant molecule has 3 carbon atoms), while another group uses a different route, the C4 mechanism (you guessed it; the relevant molecule has 4 carbon atoms). As it happens, the enzymes involved in each group have a slightly different preference for the CO2 involved (the catalytic cavity is so well adapted that the minute difference in bond length has a tiny but measurable effect; or something).
Now, back to what you tried to explain to me. AFAIK the amount of carbon in the atmosphere is minute compared to the amount available differently. I can image that there is some kind of preference of one type over the other. So, in the atmosphere (but nowhere else) one type builds up by a tiny bit. If there is a release of CO2 (say, lots of decay), it is mostly the other type that is released, so we do get a change. OK. If it is locked away from the cycle (e.g. frozen in limestone), then it no longer plays a role and we have a relatively higher ratio. Got it, I think!
However, I can't help thinking that different (climate) situations favor different groups of plants, and that they play a role here too. AFAIK sugar cane is a C4 plant and well, as you know, it favors high temperatures. Let's not rely one my memory (learned this stuff 30 years ago) and see what Google turns up. And there it is:
https://en.wikipedia.org/wiki/C4_carbon_fixation
Yes, can't remember new stuff but can recall old stuff. I"m officially old now! Wait, I digress.
So, I posit that there is a correlation between the graph that you showed and the temperature in geological time (which hopefully could be deduced through other manners). Can you expand on that?
Bert