>Forgive me for returning to an old theme that I have troubled you wi=
th in
>the past.
>
>For half a century or more, it has been clear that the path of
>starch synthesis in chloroplasts starts with triose
>phosphates and progresses to polymer formation via
>glucose-1-P rather than free glucose. Glucose is no more a product o=
f carbon
>assimilation by illuminated chloroplasts than is sucrose.
>So, why do textbooks insist that it is?.
>
>If you wish to read a recent article about this you can find it by p=
asting
>DOI 10.1007/s11120-007-9139-3
>into Google
>
>Best Christmas wishes
>>From David Alan Walker, FRS; Emeritus Professor of Photosynthesis,
>University of Sheffield, UK.
David,
This has frustrated me too, and I have always=20
ascribed it to the fact that most biology=20
textbooks are written by non-plant biologists who=20
think that chloroplasts are merely green=20
mitochondria that perform reverse respiration.=20
With that mindset, and given that glycolysis=20
clearly starts with glucose, then photosynthesis=20
must produce glucose in order for the mythical=20
symmetry to be maintained.
Yes, it's both false and foolish.
Another chloroplast/mitochondrion myth that=20
drives me bonkers the the oft-repeated=20
(mis-)statement that mitochondria and=20
chloroplasts are both bounded by a double=20
membrane. That is only true if your sole source=20
of data is electron microscopy and all you are=20
looking at is STRUCTURE. Two lines around the=20
mito--two lines around the chloro--must be the=20
same. If however, you actually start asking=20
questions about the FUNCTION of those membranes=20
(and I certainly hope my students ask those sorts=20
of questions) then you have misled the reader.=20
Just ask yourself questions like, "where is=20
chemiosmosis taking place--which membrane? Lipid=20
synthesis? Carotenoid synthesis? Metabolite=20
transport?" and the analogous double membrane=20
myth quickly falls apart.
To quote me (from "The Structure and Function of Plastids" Springer)=
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