So in glycolysis, we broke down glucose into pyruvate molecules and we also formed NADH molecules and a few ATP molecules. And this took place in the cytoplasm of the cell. Now, in the presence of oxygen, the pyruvate molecules will be moved into the matrix of the mitochondria. And in the matrix, we're going to prepare the pyruvate molecules for the citric acid cycle by a process called pyruvate carboxylation. So we form acetylco enzyme A molecules, and those acetyl coenzyme A molecules are then moved into the citric acid cycle, which also takes place in the matrix of the mitochondria. So in the cytoplasm, we have glycolysis, but inside the matrix, we have the citric acid cycle and pyruvate carboxylation.