Chemical Processes in the Formation of ATP — Role of the Mitochondria. On entry
into the cells, glucose issubjected to enzymes in the cytoplasm that convert it into pyruvic acid (a
process called glycolysis). A small amountof ADP is changed into ATP by the energy released during
this conversion, but this amount accounts for less than 5 percent of the overall energy metabolism of
the cell. About 95 percent of the cell‘s ATP formation occurs in the mitochondria. The pyruvic acid
derived from carbohydrates,fatty acids from lipids, and amino acids from proteins is eventually
converted into the compound acetyl-CoA in the matrix of the mitochondrion. This substance, in turn, is
further dissoluted (for the purpose of extracting its energy) by another series of enzymes in the
mitochondrion matrix, undergoing dissolution in a sequence of chemical reactions called the citric acid cycle,or Krebs cycle.
