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IMM is highly impermeable, not leaky. An ATP/ADP exchanger in the IMM
accomplishes this, driven by the charge gradient across the IMM. Why couldn’t a
membrane ATPase drive this movement?
(4) ATP synthase disco, some students will do anything for extra credit: DVD 14.4 <so, the ion gradient across the IMM drives ATP synthesis as well as transport. We can calculate the
amount of energy stored in that gradient and assess whether it is adequate to perform specific kinds of
work, just as we did for the Na+ gradient and the Na+/glucose symporter:> (C) Calculating the amount of energy in the proton gradient.
ÄG = F(Äp)
Äp is the “protonmotive force,”and Äp = ø 59mV(ÄpH).
ÄpH = pHcytoplasm (IMS) pH(matrix)
ø = the Vm of the inner mitochondrial membrane.
Typically, ø is a large positive number (e.g., +100 to +200 mV) because the matrix is
negatively charged with respect to the intermembrane space due to the removal of
protons from the matrix (during electron transport).
For example, if ø = + 200 mV, pH intermembrane space = 7, and pH matrix = 8, then
ÄpH = 1 and Äp = 200 mV (59 mV) = +259 mV.
And thus ÄG = F(Äp) = +25.9 kJ/mole. Because ÄG > 0, the spontaneous movement
of protons will be OUT of cytoplasm and into matrix. So under these conditions, one
mole of H+ will yield 25.9 kJ. H e r e i s a g o o d r e p r e s e n t a t i o n o f m u c h o f w h a t w e ’ v e t a lk e d a b o u t h e r e :
T C A c y c le , e l e c t r o n t r a n s p o r t , A T P s y n t h e s i s , a n d t r a n s p o r t o f m e t a b o l i t e s
a c r o s s th e m it o c h o n d r ia l m e m b r a n e . I t is F ig . 5 . 3 0 f r o m K a r p ’s C e ll &
M o le c u la r B io lo g y ....
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This note was uploaded on 06/12/2012 for the course BIOLOGY 231 taught by Professor Petethollenbeck during the Fall '10 term at Purdue.
- Fall '10
- cell biology