"Do we consider the endosymbiosis theory of Lynn Margulis to be legitimate?
I.e.
are eukaryotic mitochondria and chloroplasts related to ancestral bacteria
and blue-green algae? On the Progessive Creationist model or Young Earth
Creationist model, why would we expect such a relationship to exist?"
And, in a later reply to Stephen Jones:
"But why certain similarities and not others? Why do mitochondria and
chloroplasts look like prokaryotes? You always give the same answer to
every question. Your PC model does not seem to be a very fruitful theory:
it does not differentiate among questions or explanations. The
endosymbiosis theory accounts very nicely why certain similarities are
found and not others."
Well, I'm not a biologist and the biological knowledge I have is a little
rusty, but I'll throw out some ideas for why one would expect the organelle
structures in eukaryotes from a non-evolutionary view. In the case of both
the mitochondria and the chloroplasts, the chemical processes of oxidative
phosphorylation and photosynthesis have a fundamental dependence upon the
compartmentalization of reactants. In other words, you must have a membrane
and that membrane must contain very specialized components for the reaction
to work without the high energy reactants annihilating each other in a burst
of heat. I see a couple of implications of this for eukaryote "design".
1) The fundamental problem that the eukaryotes have relative to the
prokaryotes for carrying out these processes is one of size. Because of the
greater complexity of eukaryotes, the outer membranes contain more
receptors, channels, membrane proteins, etc. to handle the greater diversity
of molecular flow in and out of the cell. However, eukaryotes have much
less outer membrane surface space per unit of volume (just as a basketball
has less surface area than a bunch of marbles of equivalent volume). Thus,
even though a eukaryote has greater needs for membrane space, it has less
surface area in which to meet these increased demands. The obvious solution
is to create some internal membrane space. Moving all the specialized
mitochondrial-like or chloroplast-like membrane structures to an inner
membrane surface frees up a lot of outer membrane space for other
specialized structures.
2) Both the thermodynamics and kinetics of chemical reactions are dependent
upon reactant concentrations. By concentrating the reactants into small
localized structures, eukaryotes increase the efficiency of their energy
production. Prokaryotes don't need to do this, because their volume is so
much smaller and their energy needs do not require as great as efficiency.
Thus, based on these considerations, we might expect the existence of
smaller organelle structures within eukaryotic cells that share some
features with prokaryotes independent of any endosybiotic notions. This of
course doesn't explain all the similarities and for all I know my ideas
could be oversimplistic notions. But these were the ideas that readily came
to my chemist mind. :-)
__________________________________________________________
"Looking back, there's a thread of love and grace
Connecting each line and space I've known" -David Meece
==========================================================
Eddie Gene Olmstead, Jr. Chemistry Department
Asst. Professor of Chemistry Gordon College
Email: olmstead@gordonc.edu 255 Grapevine Road
Phone: (508) 927-2300 Ext. 4393 Wenham, MA 01984