Answer: Glycolysis
The first stage of cellular respiration is glycolysis that takes place in the cytosol of the cytoplasm. Basically, in this process, the glucose splits up. The enzymes break down the glucose molecules into molecules of pyruvic acid. To split the glucose molecules energy is needed and that energy is provided by the molecules of ATP.
The kerbs cycle is the third stage of the cellular respiration. The pyruvic acid molecules that were produced in the first step i.e. glycolysis, enters the mitochondrion and starts the kerbs cycle. And the energy from the molecules is stored in 16 energy carrier molecules which includes four molecules of ATP’s as well.