1. Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle
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2. Glycolysis found in almost all living organisms
occurs in the cytoplasm
does not require oxygen
first stage of aerobic cellular respiration

3. Reactions of Glycolysis
10 enzyme-catalyzed reactions
6-carbon glucose is split into two 3-carbon pyruvate molecules
net energy gain of 2 ATP
2 NAD+ are reduced to NADH
occurs in three stages

4. What does the term phosphorylation mean?
What does isomerization mean?

5. Investment (#1-3)
glucose undergoes two phosphorylations & an isomerization
2 ATP are invested
Phosphorylation: glucose --> glucose-6-phosphate
Isomerization: G6P --> fructose 6-phosphate
Phosphorylation F6P --> fructose 1,6-biphosphate
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6. Cleavage (#4-5) splits into two 3-carbon molecules: G3P & DHAP
DHAP isomerizes into G3P
Image from: olysis.htm

7. Energy pay-off (#6-10) 4 ATP are made (net 2 ATP)
some electrons & protons are released & stored for ETC (2 NADH)
Final result: 3-carbon pyruvate (x2)
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9. 2 pyruvate + 2 NADH + 2 H+ + 2 ATP
Energy Yield
2 NADH per glucose molecule
2 molecules of ATP are used
4 molecules of ATP are produced
overall net yield of 2 ATP per glucose molecule
Net Equation
glucose + 2 NAD+ + 2 ADP + 2 Pi
----->
2 pyruvate + 2 NADH + 2 H+ + 2 ATP

10. Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle

11. The Transition Reaction -Pyruvate Oxidation
Before pyruvate enters the Krebs Cycle, it is oxidised in the transition step.
Pyruvate molecules are actively transported into the mitochondrial matrix.

12. The Transition Reaction -Pyruvate Oxidation
Carbon dioxide is removed from the pyruvate
Hydrogen atoms are removed and transferred to NAD+.
reactions are carried out by enzymes
A 2-carbon compound called an acetyl group is formed & is attached to coenzyme A.
The resulting acetyl CoA can enter the Citric Acid Cycle.

13. If no ATP is created in the pyruvate oxidation stage, does that mean no energy is harvested?

14. Aerobic Respiration: Glycolysis, Pyruvate Oxidation & the Citric Acid Cycle

15. The Citric Acid Cycle (Krebs)

16. The Citric Acid (Krebs) Cycle
Acetyl CoA from the transition step is combined with a 4C compound called oxaloacetate, forming 6C citrate.
Citrate undergoes a series of decarboxylation and dehydrogenation reactions which result in the regeneration of oxaloacetate.

17. The Krebs Cycle

18. Products of the Krebs Cycle
Each turn of the Krebs Cycle produces:
4 molecules of reduced NAD+ (1 from Pyr Ox)
1 molecule of reduced FAD
1 molecule of ATP
3 molecules of CO2 (1 from Pyr.Ox.)
The Krebs Cycle turns twice for every glucose molecule broken down; per glucose molecule the yield is doubled: 8 NAD+; 2 FAD; 2ATP and 6 CO2

19. What is left of the glucose molecule at the end of the citric acid cycle?
How many ATP have been produced so far?