1. Chapter 7: How Cells Harvest Energy
How our food becomes energy for our cells (ATP)

2. How to make ATP from glucose
Can be aerobic (with oxygen) or anaerobic (without oxygen

3. ATP Review

4. Requires coenzymes NADH and FADH2
Need to collect electrons from the food and use them to drive the machine that synthesizes ATP

5. Redox Reactions

6. Redox with NAD and FAD

7. Aerobic Respiration How cells harvest energy from glucose
Glucose + 6O2  6CO2 + 6H2O + Energy
ATP + Heat

8. 4 Steps of Aerobic respiration
Glycolysis
Oxidation of pyruvate
Kreb’s cycle (aka Citric Acid Cycle)
Electron transport chain

9. Glycolysis: 6 carbon glucose to two 3 carbon pyruvates
Occurs in Cytoplasm

10. Glycolysis 6 carbon molecule broken into two 3 carbon molecules
Glucose has to be activated. This uses up 2 ATP molecules, but kick-starts the whole thing off.
4 ATPs are made during glycolysis, so a net gain of 2 ATPs

11. Glycolysis Uses an electron carrier called NADH
Each NADH molecule carries 2 electrons that it has removed from glucose
These electrons will be very important later!!!!!

12. Over-all Glycolysis
End products are 2 pyruvates (2 carbon molecules), 2 ATPs, and 4 electrons stored on 2 NADH’s

13. Oxidation of Pyruvate (Breaking 3 carbon pyruvate into a 2 carbon molecule and CO2)

14. Oxidation of Pyruvate
Pyruvate is transported into the mitochondrial matrix

15. Oxidation of Pyruvate
The 3 carbon pyruvate is broken down into a 2 carbon molecule called AcetylCoA and a CO2
The CO2 bubbles out of the mitochondria, then the cell
The AcetylCoA will be further broken down in the next step
2 NADH’s are made in this step (stealing electrons from the organic pyruvate)

16. Summary: Oxidation of Pyruvate
Carbon backbone has been broken from 3 to 2 carbons
CO2 has been made and released
2 NADH’s made (one per pyruvate)
No ATP made

17. Stage 3: Kreb’s Cycle (aka Citric Acid Cycle)
Occurs in the matrix
AcetylCoA is broken apart into CO2
Final breakdown of the carbon backbone

18. Kreb’s Cycle (In mitochondrial matrix)
The last electrons are removed from the organic molecules and put on electron carriers.
FADH2 is an electron carrier like NADH. It can carry 2 electrons on each molecule.

19. Summary Kreb’s Cycle
No more carbon-carbon bonds or electrons from glucose
6 NADH’s and 2 FADH2 created (16 electrons stored and carried)
CO2 given off
2 ATPs made

20. What to do with the electrons?
Summary so far:
Glucose carbon-backbone is totally demolished. Carbons have been released in CO2 molecules.
All available electrons have been stripped from glucose and are now carried on 10 NADH’s and 2 FADH2’s
Only net gain of 4 ATP’s
What to do with the electrons?

21. Electron Transport Chain
NADH and FADH2 drop off electrons on the inner membrane proteins
This results in recycling NAD+ and FAD, which will go back and participate in earlier events
The electrons jump from one protein to the next creating something like an electric current
This “electricity” runs something called the H+ pump. This protein moves H+ from the matrix into the inter-membrane space.

22. Electron Transport Chain
The H+ build up in the inter-membrane space and create a
big potential energy called the proton motive force

23. Electron Transport Chain
The H+ can move back into the matrix, but only through a channel attached to an enzyme called ATP Synthase, This is called chemiosmosis.
Like water running over a water-wheel, the H+ moving across the membrane powers the ATP Synthase to build ATP
Approximately 32 ATPs are made in the ETC for every glucose

24. ATP Synthesis via Chemiosmosis

25. Summary: Electron Transport Chain
NADH and FADH2 are used to power the proton pump
Protons (H+) are pumped from mitochondrial matrix into intermembrane space
These protons push through the ATP synthase making its “motor work”
ADP and Phosphate are put together to make ATP in the matrix

26. One last thing about the Electron Transport Chain
The electrons moving through the ETC will finally bind to a oxygen with 2 H+, making water
THIS IS THE REASON YOU BREATHE IN OXYGEN! To keep the electron chain moving
If no oxygen, no ATP, and you die

27. Cyanide blocks the last step of the electron transport chain, so electrons are blocked from oxygen
The whole thing gets backed up and no electrons move through.
Without “electric current”, the H+ pumps don’t build up the concentration gradient.
The ATP synthase has no H+ to drive it.
You die within minutes without the new ATP!

28. Summary of Glycolysis and Aerobic Respiration

29. Aerobic –vs- Anaerobic Respiration
If no oxygen available, the glucose molecule can’t be broken down all the way.
The results are 2 ATPs and either:
2 Lactic acids
(3 carbon molecules) Or
2 Ethanosl (2 carbon molecule) and 2 CO2 (Fermentation)

30. Lactate Fermentation Uses glycolysis Makes 2 ATPs Recycles 2 NAD+
Occurs in the muscles when not enough oxygen available to make ATP needed
Hurts!

31. Alcohol Fermentation Uses glycolysis Makes 2 ATPs Recycles 2 NAD+
Makes carbonated ethanol (beer?)
We use yeast to do this when making alcohol.
Lots of money & research goes done on this metabolic pathway.

32. Anaerobic vs Aerobic Anaerobic fermentation Aerobic respiration
Oxygen is required
Occurs in cytoplasm and
inside mitochondria
Makes about 36 ATPs
No oxygen
No mitochondria needed
Only net gain of 2 ATPs
Begins with glucose
Uses glycolysis
In cytoplasm
Uses coenzymes
FAD and NAD