STAGES OF CELLULAR RESPIRATION

First stage

glycolysis, the six-carbon sugar molecule (glucose) breaks down into 2 three-carbon molecules (pyruvic acid). The energy of the broken bonds is captured, yielding two molecules of ATP.

Second stage

the Krebs cycle, the three-carbon molecules resulting from glycolysis are broken down into carbon dioxide molecules. Both glycolysis and the Krebs cycle make ATP and NADH an electron carrier that donates electrons.

Third stage

the electron transport chain, oxygen is combined with the hydrogen atoms of NADH to make water. During electron transport, energy is continuously captured to make ATP. Because the process requires oxygen, it is sometimes called oxidative phosphorylation.