Ch 9 (Part 3): 9.4 - E.T.C./ Oxidative Phosphorylation (“Respiratory Chain”)
● So far, in glycolysis & the Krebs cycle, 1 glucose molecule has resulted in:

(2 from glycolysis, 2 from Krebs)

(2 from gly., 2 from acetyl-CoA step, 6 from Krebs Cycle)

(from Krebs Cycle)
● Following glycolysis and the Krebs cycle,
and
account for most of the energy extracted
from food
● These two electron carriers donate electrons to the
, which
via oxidative phosphorylation
ELECTRON TRANSPORT CHAIN (E.T.C.)
● E.T.C. = a collection of molecules (mostly protein complexes)
(foldings of inner membrane form CRISTAE)
The Pathway of Electron Transport
● the groups along the chain alternate between
&
states as they accept
and donate electrons
● each successive group is more electronegative than the group before it, so the electrons are “
” towards
(the
!)
 as molecular oxygen (O2) is reduced, it also picks up 2 H+ from the environment to form
.
ATP Production of the E.T.C.
Typically, the ATP produced is as follows:


(FADH2 is “dropped off” at a lower point in the E.T.C., so it generates fewer ATPs)
Chemiosmosis: The Energy-Coupling Mechanism
● Electron transfer in the electron transport chain causes proteins to
matrix to the intermembrane space (
●
H+
from the mitochondrial
)
(protons) then move back across the membrane, passing through channels in ATP synthase
● ATP synthase uses the
● This is an example of
to drive
, the use of energy in a H+ gradient to
● The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport
chain to ATP synthesis
● The H+ gradient is referred to as a
, emphasizing its
● protons then diffuse back across the membrane through the ATP synthase complex which causes the
phosphorylation of
to form
!
SUMMARY:
 most energy flows in this sequence:
Process
ATP produced by
subs. phos.
Reduced coenz.
ATP produced by
oxid. phos.
TOTAL ATPs
Glycolysis
oxid. of pyruvate
to acetyl CoA
Krebs cycle
TOTAL
● approximately 40% of energy in glucose is
●
**actual ATP total’s are slightly less – when we factor in “real” exchange rates and the energetic
cost of moving the ATP formed in the mitochondrion out into the cytosol, where it will be used**