1. Energy Generation in Mitochondria and Chloroplasts
Chapter 14
Energy Generation in Mitochondria and Chloroplasts

2. Generation of Energy
Millions of years ago there was no O2 available for oxidative phosphorylation to occur
Organisms produced energy from fermentation, still see this today
As O2 became available, a more efficient method of energy production developed
Based on the transfer of e- along the membrane

3. Organism’s Energy Source
Small amount of ATP from glycolysis in the cytosol of cells
Majority made by a membrane based process in 2 stages
Stage 1 – e- transport chain
e- transferred along e- carriers in the membrane
Stage 2 – flow of H+ down an electrochemical gradient to produce ATP
Use a complex called ATP synthase

4. Stage 1
NADH (from the Kreb’s cycle) brings in the e- and transfers them to the carrier molecules
The e- moves down the chain and looses energy at each step – as this happens, H+ are pumped across the membrane
This creates an electro-chemical gradient across the membrane

5. Stage 2
The electrochemical gradient is a form of stored energy – it has the potential to do work
The H+ can now move down the gradient and return to the other side of the membrane thru ATP synthase – in this process, generates ATP from ADP and Pi

6. Chemiosmotic Coupling
Once called the chemiosmotic hypothesis
Chemi from making ATP, osmotic because of crossing the membrane
Now known as chemiosmotic coupling

7. Mitochondria
Produce most of a cells ATP – acetyl groups in the Kreb’s cycle producing CO2 and NADH
NADH donates the e- to the electron transport chain and becomes oxidized to NAD+
e- transfer promotes proton pump and ATP synthesis in process called oxidative phosphorylation
Cells that require large amounts of energy such as the heart have large numbers of mitochondria

8. Mitochondria
Contain their own copies of DNA and RNA along with transcription and translation system (ribosomes)
Are able to regenerate themselves without the whole cell undergoing division
Shape and size dependent on what the cell’s function is

9. Mitochondria Double membrane creates 2 spaces
Matrix: large internal space
Intermembrane space:
between the membranes
Outer membrane
Inner membrane

10. Mitochondria

11. Inner Membrane
Inner membrane is the site of the e- transport chain, across which the proton pump occurs and contains ATP synthase
Inner membrane is highly folded – called cristae – increasing the surface area on which the above reactions can take place

12. High Energy e-
Mitochondria use pyruvate and fatty acids and convert it to acetyl CoA in the matrix
Citric acid cycle generates NADH and FADH2 which carry the e- to the electron transport chain

13. Summary – MUST KNOW

14. Proton Pumping
Many molecules can supply the e- - carbohydrates and fatty acids
O2 ultimate e- acceptor producing H2O as waste

15. Movement of Electrons

16. Oxidative Phosphorylation

17. Electron Transport Chain
Resides in the inner mitochondrial membrane – also called respiratory chain
15 proteins involved in the chain – grouped in 3 large respiratory enzyme complexes
NADH dehydrogenase complex
Cytochrome b-c1 complex
Cytochrome oxidase complex
Pumps protons across the membrane as e- are transferred thru them

18. Respiratory Enzyme Complexes

19. Proton Gradient e- transfer is an oxidation/reduction reaction
NADH has high-energy e- has a low electron affinity so the e- is readily passed to NADH dehydrogenase and so on down the chain
Each transfer couples the energy released with the uptake of a H+ from the matrix to the intermembrane space setting up the electrochemical gradient

20. Proton Gradient
Gradient of proton (H+) concentration across the inner mitochondrial membrane – a pH gradient with the pH in the matrix higher than in the intermembrane space
Proton pumping also generates a membrane potential – matrix side is negative and intermembrane space is positive

21. 4 Complexes in Membrane

22. Location of H+

23. Electrochemical Gradient

24. Oxidative Phosphorylation
ATP synthase is the protein complex responsible for making ATP by creating a path for H+ thru the membrane
ATP synthase is an enzyme

25. ATP Synthase
Multisubunit protein responsible for making ATP

26. Summary

27. Bidirectional Pump

28. Coupled Transport Can Move Other Molecules

29. Oxidation of Sugar and Fats