Answer
The three metabolic pathways that make up aerobic respiration are really all parts of one larger pathway because the products of early pathways (like NADH) become utilize in the last one.
Step-by-step explanation
Aerobic respiration is that type of respiration in which glucose molecule is broken down into CO2 and H2O in the presence of oxygen and 36 or 38 ATP molecules are produced.
Aerobic respiration complete in four main steps:
1. Glycolysis
In this step glucose is broken down into 2 molecules of pyruvate acid along with the production of 2 ATP molecules and 2NADH.
2. Oxidation of pyruvate
In this step pyruvate are oxidized in the presence of co-enzyme A to become Acetyl Co-enzyme A. Again 2NADH are formed in this step.
3. Kreb Cycle
It occus in mitochondria. Here acetyle coenzyme A enter Carbon fixation, reduction and regeneration phase. In this cycle 6 NADH, 2FADH2 and 2ATP are formed.
4. Electron transport chain
All NADH that are produced in above steps get oxidize and help in the production of ATP along with the release of electron and proton that help in the formation of water.