1. Cellular Respiration Part III:
Krebs Cycle

2. Electrons carried via NADH Electrons carried via NADH and FADH2
Figure 9.6-3
Electrons carried via NADH
Electrons carried via NADH and FADH2
Oxidative phosphorylation: electron transport and chemiosmosis
Glycolysis
Citric acid cycle
Pyruvate oxidation
Glucose
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
So far we have explored Glycolysis and the formation of acetyl CoA. Today we will follow the remnant glucose as it is processed through the Krebs cycle.
ATP
ATP
ATP
Substrate-level phosphorylation
Substrate-level phosphorylation
Oxidative phosphorylation

3. Citric Acid Cycle
(Krebs Cycle)
Krebs Cycle

4. Curriculum Framework
3. In the Krebs cycle, carbon dioxide is released from organic intermediates, ATP is synthesized from ADP and inorganic phosphate via substrate level phosphorylation, and electrons are captured by coenzymes.
4. Electrons that are extracted in the series of Krebs cycle reactions are carried by NADH and FADH2 to the electron transport chain.

5. Pyruvate CO2 NAD CoA NADH + H Acetyl CoA CoA CoA Citric acid cycle
Figure 9.11
Pyruvate
CO2
NAD
CoA
NADH
+ H
Acetyl CoA
CoA
CoA
Citric acid cycle
2 CO2
Here is an overview of pyruvate oxidation and the citric acid cycle.
FADH2
3 NAD
FAD
3 NADH
+ 3 H
ADP + P i
ATP

6. Krebs Cycle Occurs in the mitochondrial matrix
Releases the remaining carbons from the remnant glucose
Transfers the energy to NAD, FAD, and ADP
Details worth knowing!

7. Citric acid cycle Figure 9.12-8 Acetyl CoA Oxaloacetate Malate Citrate
CoA-SH
NADH
+ H 1
H2O
NAD
Oxaloacetate 8 2
Malate
Citrate
Isocitrate
NAD
Citric acid cycle
NADH 3 7
+ H
H2O
CO2
Fumarate
CoA-SH
-Ketoglutarate
One last NADH formation and the cycle is complete. 4 6
CoA-SH 5
FADH2
CO2
NAD
FAD
Succinate
P i
NADH
GTP
GDP
Succinyl CoA
+ H
ADP
ATP

8. Acetyl CoA 1 Oxaloacetate 2 Citrate Isocitrate H2O CoA-SH Figure 9.12a
Figure 9.12 A closer look at the citric acid cycle.
Oxaloacetate 2
Citrate
Isocitrate

9. 3 4 Isocitrate -Ketoglutarate Succinyl CoA NAD NADH + H CO2 CO2
Figure 9.12b
Isocitrate
NAD
NADH 3
+ H
CO2
CoA-SH
-Ketoglutarate 4
Figure 9.12 A closer look at the citric acid cycle.
CO2
NAD
NADH
Succinyl CoA
+ H

10. Fumarate 6 5 Succinate Succinyl CoA FADH2 FAD P i GTP GDP ADP ATP
Figure 9.12c
Fumarate 6
CoA-SH 5
FADH2
FAD
Succinate
P i
Figure 9.12 A closer look at the citric acid cycle.
GTP
GDP
Succinyl CoA
ADP
ATP

11. Oxaloacetate 8 Malate 7 Fumarate NADH + H NAD H2O Figure 9.12d
Figure 9.12 A closer look at the citric acid cycle.
H2O
Fumarate

12. Where does each atom end up?
C6H12O6
C = given off as carbon dioxide
H = transferred to NAD or FAD
O = Given off as carbon dioxide

13. So what did we get from Krebs?
Name the energy related end products of Krebs.
By what process is ATP formed?
Name the waste products.
Where do the events of Krebs occur?
Do cells in all kingdoms go through the Krebs cycle?
Where are the electrons headed?

14. So, What Did We Get From Krebs?

15. Electrons carried via NADH Electrons carried via NADH and FADH2
Figure 9.6-3
Electrons carried via NADH
Electrons carried via NADH and FADH2
Oxidative phosphorylation: electron transport and chemiosmosis
Glycolysis
Citric acid cycle
Pyruvate oxidation
Glucose
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
Figure 9.6 An overview of cellular respiration.
ATP
ATP
ATP
Substrate-level phosphorylation
Substrate-level phosphorylation
Oxidative phosphorylation

16. Curriculum Framework
f. Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates.