1. Chapter 9.3 Cellular Respiration: Electron Transport Chain

2. Cellular Respiration

3. There’s got to be a better way!
ATP accounting so far…
Glycolysis  2 ATP
Oxidation of Pyruvate  ~ 0 ATP
Kreb’s cycle  1 ATP [x2]
Life takes a lot of energy to run, need to extract more energy than just 4 ATP!
There’s got to be a better way!
What was the point again?

4. There IS a better way! Electron Transport Chain
series of molecules built into inner mitochondrial membrane
mostly integral transport proteins
transport of electrons down ETC linked to ATP synthesis
yields ~ additional 34 ATP from 1 glucose!
only when in presence of O2 (aerobic)
That’s more
like it!

5. Form fits function! Mitochondria Double membrane outer membrane
inner membrane
highly folded cristae*
fluid-filled space between membranes = intermembrane space
matrix
(mitochondrial matrix)
central fluid-filled space
Form fits function!

6. Electron Transport Chain

7. Remember the NADH/FADH2?
pyruvate oxidation & Kreb’s cycle
8 NADH
2 FADH2
Glycolysis
3GP (PGAL)
2 NADH

8. Electron Transport Chain
NADH passes electrons to ETC
H cleaved off NADH & FADH2 (oxidized)
electrons stripped from H atoms  H+ (H ions)
electrons passed from one electron carrier to next in mitochondrial membrane (ETC)
transport proteins in membrane pump H+ across inner membrane to intermembrane space as electrons move
AP Link—Ch 07: Proton Pumping
Oxidation refers to the loss of electrons to any electron acceptor, not just to oxygen.
Uses exergonic flow of electrons through ETC to pump H+ across membrane.

9. Electrons flow downhill
downhill? Uh, what
does that mean?
AP Link—Ch 07: John Kyrk’s ETC
Pumping H+ across membrane … what is energy to fuel that?
Can’t be ATP! that would cost you what you want to make!
Its like cutting off your leg to buy a new pair of shoes. :-(
Flow of electrons powers pumping of H+
O2 is 2 oxygen atoms both looking for electrons O2

10. Electrons flow downhill
Electrons move in steps from carrier to carrier downhill to O2
each carrier more electronegative
controlled oxidation
controlled release of energy
Like a game of hot potato… with each kid in line liking fries more and more!
AP Link—Ch 07: ETC (TSOB)
Electrons move from molecule to molecule until they combine with O & H ions to form H2O
It’s like pumping water behind a dam -- if released, it can do work

11. ATP ATP Why the build up H+? ATP ATP synthase ATP ADP + Pi  ATP
OK! I get the point! Can I take my fingers out of my ears? Wait a second… I don’t even have any bloody arms! What the heck…
ATP synthase
enzyme in inner membrane of mitochondria
ADP + Pi  ATP
only channel permeable to H+
H+ flow down concentration gradient = provides energy for ATP synthesis
“proton-motive” force
molecular power generator!
flow like water over water wheel
flowing H+ cause change in shape of ATP-synthase enzyme
powers bonding of Pi to ADP H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP

12. ATP synthesis Chemiosmosis couples ETC to ATP synthesis
build up of H+ gradient just so H+ could flow through ATP synthase enzyme to build ATP
So THAT’S
the point!
AP Link—Ch 07: Chemiosmosis

13. Peter Mitchell 1961 | 1978 Proposed chemiosmotic hypothesis
revolutionary idea at the time
“proton motive force”

14. Cellular Respiration
So here it all is!

15. Summary of Cellular Respiration
C6H12O6
6O2
6CO2
6H2O
~36 ATP  +
Where did the glucose come from?
Where did the O2 come from?
Where did the CO2 come from?
Where did the H2O come from?
Where did the ATP come from?
What else is produced that is not listed above?
Why do we breathe…?
AP Movie—Ch 07: Cell Respiration Animation
Where did the glucose come from?
from food eaten
Where did the O2 come from?
breathed in
Where did the CO2 come from?
oxidized carbons cleaved off of the sugars
Where did the H2O come from?
from O2 after it accepts electrons in ETC
Where did the ATP come from?
mostly from ETC
What else is produced that is not listed in this equation?
NAD, FAD, heat!

16. Why do we breathe?
What is the final electron acceptor in electron transport chain? O2
So what happens if O2 unavailable?
ETC backs up
ATP production ceases
cells run out of energy
and you die!
What if you have a chemical that punches holes in the inner mitochondrial membrane?
Whoops!

17. ATP Any Questions? The Point is to Make ATP! What’s the point?
AP Movie—Ch 07: Cell Respiration Animated
The Point is to Make ATP!
Any Questions?