1. Cellular Respiration Electron Transport Chain

2. Cellular respiration

3. What’s the point?
ATP
The Point is to Make ATP!

4. There’s got to be a better way!
ATP accounting so far…
Glycolysis  2 ATP
Kreb’s cycle  2 ATP
Life takes a lot of energy to run, need to extract more energy than 4 ATP!
There’s got to be a better way!
What’s the Point?

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

6. Mitochondria Double membrane * form fits function! outer membrane
inner membrane
highly folded cristae*
fluid-filled space between membranes = intermembrane space
matrix
central fluid-filled space
* form fits function!

7. Electron Transport Chain

8. Remember the NADH? Kreb’s cycle Glycolysis 8 NADH 2 FADH2 4 NADH PGAL

9. Electron Transport Chain
NADH passes electrons to ETC
H cleaved off NADH & FADH2
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
High concentration is here – therefore pump is used
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.

10. electrons flow downhill to O2
But what “pulls” the electrons down the 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
electrons flow downhill to O2

11. Electrons flow downhill
Electrons move in steps from carrier to carrier downhill to O2 : less energy as we go
each carrier more electronegative
controlled oxidation
controlled release of energy
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

12. Why the build up H+? ATP synthase ADP + Pi  ATP
only channel permeable to H+
H+ flow down concentration gradient = provides energy for ATP synthesis
flowing H+ cause change in shape of ATP synthase enzyme
powers bonding of Pi to ADP
ATP synthase
enzyme in inner membrane of mitochondria
ADP + Pi  ATP

13. 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!

14. Cellular respiration

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 in this equation?
Why do we breathe?
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. Taking it beyond…
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?

17. What’s the point?
ATP
The Point is to Make ATP!

18. Any Questions??