Just when you think you’re out of the woods after Glycolysis–you say to yourself: “I can take a breather”–the Krebs Cycle (a.k.a. The Citric Acid Cycle, or the oxidation of citrate) makes its appearance.
It can be just as complex, if not more, than Glycolysis. But the main thing that we have to take into account about this catabolic pathway–and catabolism of carbohydrates is all about accounting–is the redox reactions mediated by the enzymes of this pathway. This short animation should give us a brief review of how oxidation and reduction (redox) occur.
The following animation–embedded here via Khan Academy–shows a very good summary of the Citric Acid Cycle (notice the importance that the lecturer gives to “the big picture”, which in the Krebs Cycle means the enzyme regulated oxidation of a carbohydrate).