Summarize the aerobic phases of cellular respiration?

1. Kreb's cycle breakdown the acetyl CoA into CO2 and H2O. The energy released is stored in the reducing powers (NADH and FADH2).

2. The electron transport chain oxidized the reducing powers into their oxidized forms. During this electron transport, the proton concentration gradient is produced across the inner mitochondrial membrane that drives ATP synthesis.

Explanation:

Kreb's cycle and electron transport chain (ETC) are the aerobic phases of cellular respiration. The carbon skeleton glucose enters Kreb's cycle in the form of acetyl CoA and is completely oxidized into CO2 and H2O. For one molecule of glucose, Kreb's cycle produces four molecules of CO2, 6 NADH, and 2 FADH2. In addition, two ATP are also formed by substrate-level phosphorylation.

The NADH and FADH2 enter ETC and are oxidized by giving their electrons to the molecular oxygen. Here, some of the energy of electrons is used to pump the protons from the matrix to intermembrane space. The resultant proton concentration gradient drives ATP synthesis. NADH produces the proton gradient enough to drive around 3 ATPs while FADH2 supports the formation of around 2 ATPs by oxidative phosphorylation.