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Fwd: [Plant-education] Glucose is no more a product

Bob Wise via plant-ed%40net.bio.net (by wise from uwosh.edu)
Wed Dec 19 15:36:07 EST 2007

The bottom half of my last email got cut off.

Chloroplasts are enclosed by a double-membrane 
envelope composed of an outer and an inner 
membrane (Fig. 10b). A common misconception seen 
in most biology texts is that the double-membrane 
envelope of the chloroplast is similar to the 
double-membrane of the mitochondrion.  This is 
conceptually incorrect.  It is true that the 
outer mitochondrial membrane and the outer 
chloroplast envelope membrane are analogous in 
that both are rather minimal barriers between the 
cytoplasm and the organellar interior (Salomon et 
al., 1990; Sardiello et al., 2003; Weber, Chapter 
14).  However, the inner mitochondrial membrane 
and the inner chloroplast envelope membrane are 
very different in structure and function.  The 
inner mitochondrial membrane is the site of 
oxidative phosphorylation, while the inner 
chloroplast envelope membrane controls metabolite 
transport (Weber, Chapter 14) and synthesizes 
fatty acids, lipids, carotenoids, and prenyl 
lipids (Cuttriss et al., Chapter 16; Döermann, 
Chapter 17).  The inner chloroplast envelope 
membrane has no corresponding structure in the 
mitochondrion, making the thylakoid membrane (the 
site of photophosphorylation) the operative 
counterpart to the inner mitochondrial membrane. 
Therefore, when textbooks make statements such 
as, "Like chloroplasts, (mitochondria) both have 
an outer membrane and an inner membrane" (Raikhel 
and Chrispeels, 2000) they run the risk of 
misleading the reader into believing that the two 
organelles are bounded by homologous or analogous 
double-membraned structures, which they clearly 
are not. (Wise, R.R.  2006.  The diversity of 
plastid form and function.  In:  Wise, R.R. and 
J.K. Hoober.  The Structure and Function of 
Plastids, Springer, Amsterdam.  pp. 3-26.)
Robert R. Wise
Dept. of Biology
UW Oshkosh
800 Algoma Blvd
Oshkosh, WI 54901
(920) 424-3404 (tel)
(920) 424-1101 (fax)

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