1. Aerobic Respiration
Section
9:2

2. Overview
Krebs Cycle: the oxidation of glucose and the reduction of NAD+ to NADH.
Electron Transport Chain: where NADH is used to make ATP.
Krebs or the ETC. will not occur unless, CO2, H2O and O2 are ALL present.

3. Aerobic Respiration – Oxygen Present
Occurs in the mitochondria of eukaryotes and the cytosol of prokaryotes
Pyruvic acid from glycolysis diffuses in from the cytosol to the mitochondrial matrix
The space inside the inner membranes

4. outer mitochondrial membrane
inner compartment
outer compartment
cytoplasm
outer mitochondrial membrane
inner mitochondrial membrane
(see next slide)
Fig. 7.5a, p. 114

5. CO2 is lost in this process and NAD is reduced to NADH and H+.
Aerobic Respiration
Pyruvic acid joins with coenzyme A (CoA) to form acetyl CoA – 2 carbons
CO2 is lost in this process and NAD is reduced to NADH and H+.

6. Krebs Cycle
A biochemical pathway that breaks down acetyl CoA producing CO2, hydrogen, and ATP.
5 steps to the Krebs cycle

7. Step 1
The 2-carbon acetyl CoA combines with a 4-carbon compound, oxaloacetic acid, to form a 6-carbon molecule, citric acid
This step regenerates coenzyme A

8. PREPARATORY STEPS
pyruvate
coenzyme A (CoA)
NAD+
NADH
(CO2)
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate
H2O
NADH
H2O
NAD+
malate
isocitrate
NAD+
H2O
NADH
fumarate
a-ketogluterate
FADH2
CoA
FAD
NAD+
NADH
succinate
CoA
succinyl–CoA
Fig. 7.6, p. 115
ATP
ADP + phosphate group (from GTP)

9. Step 2
Citric acid releases a CO2 and a hydrogen to form a 5-carbon compound
NAD+ accepts an H+ to become NADH and H+.

10. PREPARATORY STEPS
pyruvate
coenzyme A (CoA)
NAD+
NADH
(CO2)
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate
H2O
NADH
H2O
NAD+
malate
isocitrate
NAD+
H2O
NADH
fumarate
a-ketogluterate
FADH2
CoA
FAD
NAD+
NADH
succinate
CoA
succinyl–CoA
Fig. 7.6, p. 115
ATP
ADP + phosphate group (from GTP)

11. Step 3
The 5-carbon compound releases CO2 and H+ to form a 4-carbon compound.
NAD+ is reduced again to NADH and One molecules of ATP is made

12. PREPARATORY STEPS
pyruvate
coenzyme A (CoA)
NAD+
NADH
(CO2)
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate
H2O
NADH
H2O
NAD+
malate
isocitrate
NAD+
H2O
NADH
fumarate
a-ketogluterate
FADH2
CoA
FAD
NAD+
NADH
succinate
CoA
succinyl–CoA
Fig. 7.6, p. 115
ATP
ADP + phosphate group (from GTP)

13. The 4-carbon compound releases hydrogen
Step 4
The 4-carbon compound releases hydrogen
The hydrogen forms with FAD+ to form FADH2. FADH is another electron acceptor.

14. PREPARATORY STEPS
pyruvate
coenzyme A (CoA)
NAD+
NADH
(CO2)
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate
H2O
NADH
H2O
NAD+
malate
isocitrate
NAD+
H2O
NADH
fumarate
a-ketogluterate
FADH2
CoA
FAD
NAD+
NADH
succinate
CoA
succinyl–CoA
Fig. 7.6, p. 115
ATP
ADP + phosphate group (from GTP)

15. The 4-carbon compound releases a hydrogen to REFORM oxaloacetic acid
Step 5
The 4-carbon compound releases a hydrogen to REFORM oxaloacetic acid
NAD+ is reduced again to NADH and H+

16. PREPARATORY STEPS
pyruvate
coenzyme A (CoA)
NAD+
NADH
(CO2)
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate
H2O
NADH
H2O
NAD+
malate
isocitrate
NAD+
H2O
NADH
fumarate
a-ketogluterate
FADH2
CoA
FAD
NAD+
NADH
succinate
CoA
succinyl–CoA
Fig. 7.6, p. 115
ATP
ADP + phosphate group (from GTP)

17. Glycolysis, produces 2 NADH and 2 pyruvic acid, 2 ATP.
One molecule of glucose from glycolysis needs 2 turns of the Krebs to produce:
Summary: 10 NADH, 2 FADH, 4 ATP, 4 CO2. The 10 NADH and 2 FADH (both electron acceptors) will drive the next stage of cellular respiration in the Electron Transport Chain.

18. Electron Transport Chain
ATP is produced when NADH and FADH2 release hydrogen atoms, regenerating NAD+ and FAD+.
This occurs along the lining of the inner membranes of the mitochondria.

19. Steps of ETC
1. Electrons from the hydrogens of NADH and FADH2 are passed along a series of molecules, losing energy along the way.

20. 2. This energy pumps protons from the matrix to the other side of the membrane.
A concentration gradient of protons is created across the inner membrane.

21. OUTER COMPARTMENT
NADH
INNER COMPARTMENT
Fig. 7.7a, p. 116

22. 3. This high concentration drives chemiosmosis ( ATP production) into the matrix. ATP synthase is located in the inner membrane. ATP is made as protons move down their concentration gradient in the mitochondria.

23. Oxygen’s Role
Oxygen is the final electron acceptor, accepting electrons from the last molecule in the ETC.
This allows ATP to continue to be synthesized.
Oxygen also accepts the protons, part of the hydrogen atoms from NADH and FADH.
This combination of electron, protons and oxygen forms WATER!!!!! O2 + e- +H- = H2O

24. ATP
NADH
INNER
COMPARTMENT
ADP + Pi
Fig. 7.7b, p. 116

25. Energy Yield
Per molecule of glucose, 38 ATP’s are produced. 4 in glycolysis and Krebs, 34 in ETC.
66% efficiency
C6H12O6 + 6O2  6CO2 + 6H2O + energy

26. 1 Pyruvate from cytoplasm enters inner mitochondrial compartment.
OUTER COMPARTMENT
4 As electrons move through the transport system, H+ is pumped to outer compartment.
NADH
3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems.
acetyl-CoA
NADH
Krebs Cycle
NADH
ATP
ATP
5 Oxygen accepts electrons, joins with H+ to form water.
2 Krebs cycle and preparatory steps: NAD+ and FADH2 accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms.
ATP
ATP
free oxygen
ADP + Pi
INNER COMPARTMENT
6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation.
Fig. 7.5b, p. 114

27. Raw Materials of Photosynthesis Light reaction Dark Reaction
C-A
ATP
NADPH O2
Co2
RuBP
PGA
PGAL
Glucose

28. Important Raw materials Glycolysis Fermentation
Glucose
Pyruvic Acid
2 ATP
NADH
Pyruvic acid- reactant
Lactic Acid
Ethyl Alcohol
NAD

29. Important raw materials in the Krebs Cycle E.T.C.
Pyruvic acid – Acetyl CoA
Acetyl-CoA – Oxaloacetic Acids- Citric Acid
NADH and FADH
4 ATP
CO2
NADH
FADH
34 ATP
Water