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STAGE 4:ELECTRON TRANSPORT CHAIN (ETC) AND CHEMIOSMOSIS
Recall Glycolysis
DIGESTION
Which was followed by…
So, what do we have at this point?
A small amount of ATP (the useful energy for
cell functions)
and...
LOTS OF REDUCED CARRIERS: NADH and FADH2
• the electrons are the “currency” with which the bulk of the energy is obtained
Now this “currency” (the electrons) need to be exchanged for the “currency” used by cells.....
So....how do we go from
ELECTRONSTO
ATP
Electron Transport Chain
A series of redox reactions moves electrons along the inner membrane of the mitochondria
Components are arranged in order of increasing EN
The Players
Label your diagram…use
different colours!
Electron Transport Chain
NADH gives up 2 e- to the first protein- complex (NADH dehydrogenase)
e- flow is very exergonicThis E is used to pump protons out
of matrix and into intermembrane space
Electron Transport Chain
Oxygen is used to oxidize the last protein (Strips off the 2e- )
With 2 protons (H+) from the matrix, H2O is formed
Where does the oxygen come from?
FADH2 and NADH do not transfer their e- in the same way
NADH passes e- to the first protein complex NADH dehydrogenase (pumps 3 p+)
FADH2 passes e- to Q (pumps 2 p+)
But what about FADH2?
Solution?A shuttle system is used to pass e-
from cytosolic NADH (produced during glycolysis) to the matrix
One more problem…the inner mitochondrial
membrane is impermeable to NADH!
2 Types of Shuttles
Glycerol-Phosphate Shuttle most commonTransfers e- from cytosolic NADH to
FAD to produce FADH2
Aspartate ShuttleTransfers e- to NAD+ forming NADH
Electron Transport Chain
[p+ ] builds up in intermembrane space
p+ are actually Hydrogen ions...so an electrical gradient also exists
the [gradient] and electrical gradient create the force needed to push the protons back into the matrix (called the Proton Motive Force or PMF)
BUT…
the membrane is (mostly) impermeable to ions
How do the protons pass through the
membrane?
through facilitated diffusion through
the centre of an ATP synthase complex
ELECTRON TRANSPORT
Chemiosmosis As H+ moves into the matrix through ATP
synthase, energy is released The energy is used to phosphorylate ADP
to form ATP (oxidative phosphorylation) Newly formed ATP are transported to the
cytoplasm by facilitated diffusion (where they will be used to drive endergonic processes)
Can we get energy from other food sources?
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