Make your own free website on

Everything You Need To Know About Cellular Respiration


What Is Cellular Respiration?
Transition Reaction
Krebs Cycle
Electron Transport Chain

Glycolysis is made up of two parts, Glycolysis I and II.

What is Glycolysis?
Glycolysis is a series of endothermic and exothermic  reactions that converts glucose into pyruvate with the use of a small amount of ATP.

Glycolysis takes place in the cytosol or cytoplasm in the cell. The energy from glycolysis powers all the systems that maintain homeostasis

Glycolysis I

     To start Glycolysis endothermic energy is required. The energy used to start it off comes from ATP from the first reaction of glycolysis I, substrate level phosphorylation what happens is enzymes transfers a Pi from one substrate to another. This can either remove a phosphate from ATP or add a phosphate to ADP. 1 molecule of ATP is used to add a phosphate to glucose to make glucose -6- phosphate. 1 molecule of ATP is used to phosphorylize fructose -6- phosphate to fructose -1,6- diphosphate. These are both reorganized to make two molecules of PGAL (glyceraldehyde -3- phosphate) These two molecules of PGAL are the primary reactants for glycolysis II.

Glycolysis II

     Glycolysis II is made up of exothermic reactions. The PGAL that was formed in Glycolysis I is now oxidized or broken down. The electrons are then taken up by NAD and reduces it. The H+ adds on to NAD to form NADH+. Now the oxidized PGAL now takes on another phosphate to form PGAP (1,3 - diphosphoglycerate). Two molecules of PGAP are formed for each glucose molecule that enters into glycolysis. Then two molecules of ADP with the help of enzymes take a phosphate group from PGAP to form PGA (3- phosphoglycerate), So now there is two molecules of ATP made. One for each molecule of PGAP. At this point there were two molecules of ATP synthesized and two molecules to catalyze glycolysis. The net gain of ATP is zero. Now the two molecules of PGA are oxidized leaving off or releasing two water molecules and leaving PEP (phosphenlpyriuvate). Two molecules of ADP with the help from enzymes remove the remaining phosphate from PEP to form two ATP. The final product of both Glycolysis I and II is pyruvate. Also the net gain of two molecules of ATP. These are used as ingredient in the rest of aerobic respiration.

Glyco- from sugar, glucose                                                

Lysis- breaking down of a cell                                       

Glycolysis- Breaking down of sugar

Cellular Respiration