[Rajiv]

Take it easy greg. Sofar as reactions are concerned you must learn them by heart and by time it will be no problem at all to remember all of them. However you must be clear of the fact why they are there.
It is (not only but mainly) about producing maximum possible ATP.
Just draw a sketch: what are inputs and what comes out, and where the outputs are used.

Simplified:
anaerob.
Glc ---->lactat // 2 ATP

Aerob.
1. Glc ---->Pyruvate // 2 ATP
2. Pyruvate---->Acetyl-CoA // NADH/H+(=3ATP)
3. Acetyl-CoA in Krebs cycle----> 3NADH/H+(=3*3ATP), FADH2(=2ATP), GTP

4. Oxd Phosp.---> NADH/H+, FADH2 are used as proton donator, they create proton gradient in mitoch. intermembrane, which is needed to generate ATP out of ADP + P.

So in aerobic condition, a cell can generate 16 times more ATPs than in anaerobic condition. This is all you need to understand. Erythrocytes eg can only produce 2 ATP per glycolysis per Glc since mitoch. are missing for ox. phosph.

Moreover krebs cycle is a junction for many other metabol. processes. Like Gluconeogenesis.

good luck