1. ETC with Oxidative Phosphorylation
Cell Respiration Part 4
ETC with Oxidative Phosphorylation

2. Mitochondria (click here!)
Site of Krebs Cycle and ETC
Rod shaped
Filamentous
Size 0.5 – 1.0 um diameter
Flexible shape
Number of mitochondrion in cell vary in type of cell

3. Structure of Mitochondria
Surrounded by envelope of two phospholipid bilayers
Double membraned
Outer membrane
Permeable to small molecules
Inner membrane
Site of ETC
folded inwards to make cristae (increase SA)
Active cells= longer, more densely packed cristae…why?
Less permeable to molecules
Studded with ATP Synthase (appear as tiny spheres attached to inner membrane as stalks)
Contain many more proteins that function in ETC
Intermembrane space
In between outer and inner membrane
LOW pH because of high concentration of H+ ions
Matrix
Higher pH than intermembrane spce
Site of link reaction and Krebs cycle
Contains enzymes needed for these reactions
Contains small (70S) ribosomes
Contains several copies of looped mitochondrial DNA
Contains the ATP formed by the ETC

4. Oxidative Phosphorylation WITH the Electron Transport Chain
Final stage of AEROBIC respiration
Energy for the phosphorylation of ADP to ATP comes from the ETC
Occurs in the inner mitochondrial membrane

5. Electron Transport Chain
Reduced NAD and FAD are passed to the ETC
Hydrogens are removed from the carriers
Hydrogen is split into a hydrogen ion (H+) and an electron (e-)
Electron is Highly energized
Passed off to first electron carriers in ETC

7. Electron Carriers in the ETC
Electron carriers in ETC associated with membrane proteins
“Protein Complexes”
Respiratory Unit
Functional unit of electron carriers and proteins
Consists of one of the proteins arranged in such a way that electrons can be passed from one to another, DOWN the energy gradient (high low energy)
As e- move form one carrier to the next, energy is released
Energy used to ACTIVELY TRANSPORT protons (H+) from matrix to intermembrane space (between the inner and outer membrane)
Creates high concentration of H+ ions in intermembrane space
Establishes concentration gradient

9. Electron Carriers in the ETC
Electron carriers in ETC associated with membrane proteins
“Protein Complexes”
Four Types
Complex I: NADH-coenzyme Q oxidoreductase
establishes the hydrogen ion gradient
Pumps four hydrogen ions across the membrane from the matrix into the intermembrane space
Complex II: Succinate Dehydrogenase
receives FADH2
bypasses complex I
delivers electrons directly to the electron transport chain.
Mobile Carrier Molecule: Ubiquinone (Q)
accepts the electrons from both complex I and complex II and delivers them to complex III
Complex III: Cytochrome b-c1 complex
pumps protons through the membrane
passes its electrons to cytochrome c (mobile carrier molecule)for transport to the fourth complex of proteins and enzymes
Complex IV : Cytochrome c oxidase
reduces oxygen
the reduced oxygen then picks up two hydrogen ions from the surrounding medium
Produces water.

10. Hydrogen Ion Gradient builds up…now what?
Once the H+ ion concentration has built up in intermembrane space, H+ ions will diffuse back into matrix by FACILITATED DIFFUSION (why?)
CHEMOSMOSIS
Uses channel protein associated with ATP SYNTHASE
As hydrogen ions diffuse through, ATP Synthase attaches an inorganic phosphate to ADP, creating ATP

11. Role of Oxygen Final electron acceptor
Very electronegative
Waits in matrix, outside cytochrome C oxidase
As electrons move down the gradient, they will REUNITE with the hydrogen ions from which they were split and attach to oxygen, creating WATER
When electrons and H+ ions re added to oxygen, it is “reduced” to water
“Oxygen is the final electron acceptor for the hydrogens removed from the respiratory substrate during glycolysis, the link reaction, and the Krebs cycle”

12. ATP Production at the End of the ETC
Theoretically:
Three molecules of ATP produced from 1 molecule of reduced NAD
Two molecules of ATP produced from reduced FAD
Only possible when ADP and inorganic phosphate is present in matrix
25% of the total energy yield of electron transfer is used for transport:
ADP into the mitochondria
ATP into the cytoplasm
Realistic totals:
1 reduced NAD = 2.5 molecules of ATP
1 reduced FAD = 1.5 molecules of ATP
Number of ATP molecules produced in oxidative phosphorylation varies in the type of cell and tissue
Depends on how much energy is needed to move substances in and out of the mitochondria

13. Key things to Remember:
Energy released in the ETC powers the production of the proton gradient across the inner membrane of the mitochondria
Due to this gradient, ATP synthase is able to turn to produce ATP by chemiosmosis
Oxidative phosphorylation:
REGENERATES NAD+
splits hydrogen atoms into hydrogen ions and electrons
Involves the transfer of electrons along a chain of carriers from higher to lower energy
Oxygen is the final electron acceptor

15. Click Here For A Movie!