Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!frist
From: frist@ccu.umanitoba.ca
Newsgroups: sci.bio
Subject: Re: Quiz time
Message-ID: <1991Apr28.211726.11649@ccu.umanitoba.ca>
Date: 28 Apr 91 21:17:26 GMT
References: <1991Apr24.134105.25827@pa.dec.com> <212@tdatirv.UUCP> <1991Apr26.142343.9514@ccu.umanitoba.ca> <221@tdatirv.UUCP>
Organization: University of Manitoba, Winnipeg, Canada
Lines: 61

In article <221@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes:
>In article <1991Apr26.142343.9514@ccu.umanitoba.ca> frist@ccu.umanitoba.ca writes:
>>Ribulose bisphosphate is the acceptor for CO2 in the reductive pentose
>>cycle aka Calvin cycle for carbon fixation. This reaction is catalyzed
>>by ribulose bisphosphate carboxylase/oxygenase (RUBISCO). Ribulose
>>bisphosphate is, therefore, about as intimately involved in photosynthesis
>>as you can get!
> 
>>For those interested, the reaction in plants with C3 metabolism is
>>
>>3 Ribulose-bis-P + 3 CO2 --> 6 glyceraldehyde-3-phosphate
>
>Quite.  As I remeber the details of this is there not also a
>+ 12 H (in the form of NADH or some such, from the light reaction of
>	photosynthesis)
>
>Also, as I add up the numbers, doesn't this reaction also produce something
>else (like 3 H2O ??).  [I seem to remember that the generic formula for
>sugars (i.e. carbohydrates) is (CH2O)n].
>
>leading to a reaction formula (for the dark reaction) of:
>3 Ribulose-bis-P + 3 CO2 + 6 NADH2 -> 6 Glyceraldehyde-3P + 3 H2O + 3 NAD
>[Of course the light reaction involved removing the hydrogen from *6* H2O].
>
>uunet!tdatirv!sarima				(Stanley Friesen)

Okay, here it is, straight out of PLANT BIOCHEMISTRY (Goodwin & Mercer):

(6) D-ribulose 1,5-diphosphate (RuDP aka RuBP)
                    |
                    v
(6)        [enediiol of RuDP]
                    | + 6CO2
                    v
(6)  2-carboxy-3keto-D-ribitol 1,5-diphosphate 
                    | + 6H20 
                    v
(12) D-3-phosphoglyceric acid 
                    |<- 12 ATP
                    |-> 12 ADP
                    v
(12) 1,3 Diphosphoglyceric acid
                    |<- 12 NADPH + 12H+ 
                    |-> 12 NADP+ + 12Pi 
                    v
(12) 3-Phosphoglyceraldehyde
                    |
                    v

and so forth through the Calvin cycle, and all of this effort just to make
ONE hexose sugar (Fructose 6-phosphate).

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Brian Fristensky                |  
Department of Plant Science     | "There's a big ... machine in the sky...
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