1. Aerobic Respiration

2. Remember… Cellular respiration is the breakdown of glucose into energy
So far we have learned about glycolysis
Glycolysis is the first of many steps in cellular respiration
Glycolysis happens in the cytoplasm

3. Remember…
Glycolysis is the formation of 2 ATP, 2 NADH and 2 pyruvate from the energy that is given off by the splitting of glucose
It is a complex process that involves energy investment and energy payoff

4. Before The Next Step
After glycolysis and before our next step some very important things happen
We have to first determine the type of respiration that will follow
If there are mitochondria and oxygen present most cells will perform aerobic respiration

5. Before The Next Step
Before aerobic respiration happens a series of reactions happens to pyruvate
These reactions happen in the mitochondria
This is because the mitochondria is the sight of aerobic respiration

6. Before The Next Step
Pyruvate is acted on by a large multiple enzyme complex that performs three key reactions in a short time
1. Pyruvate loses a carboxyl group (COO-) which is transported out of the cell as CO2

7. Before The Next Step
2. The remaining 2 carbon compound is oxidized (loses electrons) to create a molecule of NADH from NAD+ 3. A compound called coenzyme A joins in with the two carbon compound to form acetyl CoA

8. Intro Citric Acid Cycle
The next step in the process is the Citric Acid Cycle
This cycle can also be called the “Krebs” cycle in honor of Hans Krebs
Hans Krebs was a German/British researcher that discovered most of the steps to the cycle

9. Intro Citric Acid Cycle
The purpose of the Krebs Cycle is to create ATP, 3 NADH and FADH2 (another electron carrier)
This will create a large amount of electrons that can be carried to the next step in aerobic respiration
A byproduct of this series of reactions is CO2
This all happens in the mitochondrial Matrix

10. Citric Acid Cycle
Acetyl CoA enters the cycle and gets the whole cycle started by leaving. The remaining 2 carbon compound will combine with a 4 carbon compound called oxaloacetate. The product of this reaction is the 6 carbon compound Citrate (does that look familiar?)
Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate.

11. Citric Acid Cycle
Acetyl CoA enters the cycle and gets the whole cycle started by leaving. The remaining 2 carbon compound will combine with a 4 carbon compound called oxaloacetate. The product of this reaction is the 6 carbon compound Citrate (does that look familiar?)
Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate.
The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate.
The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate.
Finally the Malate is converted to our original 4 carbon compound oxaloacetate when it loses two electrons and creates another molecule of NADH

12. Citric Acid Cycle
3. The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosphorylation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound called Succinate.
4. The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate.
5. Finally the Malate is converted to our original 4 carbon compound Oxaloacetate when it loses two electrons and creates another molecule of NADH
Acetyl CoA enters the cycle and gets the whole cycle started by leaving. The remaining 2 carbon compound will combine with a 4 carbon compound called oxaloacetate. The product of this reaction is the 6 carbon compound Citrate (does that look familiar?)
Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate.
The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate.
The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate.
Finally the Malate is converted to our original 4 carbon compound oxaloacetate when it loses two electrons and creates another molecule of NADH

13. Citric Acid Cycle
Acetyl CoA enters the cycle and gets the whole cycle started by leaving. The remaining 2 carbon compound will combine with a 4 carbon compound called oxaloacetate. The product of this reaction is the 6 carbon compound Citrate (does that look familiar?)
Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate.
The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate.
The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate.
Finally the Malate is converted to our original 4 carbon compound oxaloacetate when it loses two electrons and creates another molecule of NADH

14. Citric Acid Helper!

15. So What Just Happened?
You might have just felt like you were punched in the gut…
That’s ok
Here is something to make you feel better

16. So What Just Happened? Ok… back to business
The Krebs Cycle produced some very valuable things
2 ATP
6 Molecules of NADH (each carrying 2 electrons)
2 Molecules of FADH2 (carrying 2 electrons)
4 Molecules of CO2

17. These are the totals for all the steps of aerobic respiration so far…
Glycolysis
Pre Citric Acid
Citric Acid
2 Net ATP
2 ATP
2 NADH
6 NADH
2 FADH2
2 CO2
4 CO2

18. What’s Next? So far we have produced 4 ATP, 8 NADH and 2 FADH2
This is not a lot of energy
Considering the process of a cell membrane pump takes one ATP, we would quickly run out of energy for the cell

19. What’s Next?
The next step is going to convert electrons into a huge energy payoff
The process of oxidative phosphorylation is where stored electrons are used to build an H+ concentration and power ATP Synthase

20. Oxidative Phosphorylation
The process of OP starts in the inner membrane
The electron transport chain will be responsible for using electrons to pump H+ ions out of the matrix
This process builds a concentration gradient outside of the mitochondrial maxtix

21. Oxidative Phosphorylation
Moving the electrons from place to place are protein complexes and mobile electron carriers
These complexes pump the H+ ions creating the gradient
This will be used later to create ATP

22. Oxidative Phosphorylation
Once the electrons go through the electron transport chain, they must end up somewhere
They cannot just hang out in the matrix
Oxygen accepts the electrons and two spare H+ ions to create H20
This means the oxygen you breathe is the final electron acceptor

23. Oxidative Phosphorylation
Once there is a proper concentration gradient, the H+ ions diffuse back into the matrix through ATP Synthase
This enzyme will use the H+ ions to create ATP
This process is called chemiosmosis

24. I Care… Why?
Oxidative phosphorylation creates the bulk of the energy that you and I use
It creates roughly 28 molecules of ATP per glucose
That is over 7 times the amount produced by glycolysis and the citric acid cycle

25. I Care… Why?
This means that cells that are able to perform aerobic cellular respiration have a huge advantage when it comes to total ATP energy
They create more energy per molecule of glucose

26. Oxidative Phosphorylation
The Totals
These are the totals for all the steps of aerobic respiration so far…
Glycolysis
Pre Citric Acid
Citric Acid
Oxidative Phosphorylation
Totals
2 Net ATP
2 ATP
28 ATP
32 ATP
2 NADH
6 NADH
USES NADH
2 FADH2
USES FADH2
2 CO2
4 CO2
6 CO2
6 H20
6 H2O