AAT Bioquest

What are the steps of cellular respiration?

Posted May 30, 2023


There are 3 main steps of cellular respiration: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation in that order. During glycolysis, the 6-carbon molecule becomes broken down into two 3-carbon pyruvate molecules. ATP is subsequently generated in the process, which occurs in the cytosol of the cytoplasm. The pyruvate then moves into the mitochondrial matrix where the transition step, pyruvate oxidation, occurs. Pyruvate dehydrogenase converts the three-carbon pyruvate to the two-carbon acetyl-CoA. The Krebs cycle then occurs when acetyl-CoA joins with a four-carbon oxaloacetate to form the six-carbon citrate. It takes two completions of the Krebs cycle to break down the original glucose since each molecule of glucose produces 2 pyruvate molecules. During the last step, NADH and FADH2 generated in other steps donate their electrons to the electron transport chain. As electrons move down the chain, energy becomes released and utilized to pump protons out of the matrix, forming the proton gradient. Protons then flow into the matrix and use ATP synthase to make ATP. The entire process of cellular respiration generates 36-38 ATP per molecule of glucose. 

Additional resources



PhosphoWorks™ Colorimetric ATP Assay Kit

Amplite® Colorimetric Pyruvate Assay Kit