First, glycolysis is not a cycle,it is a “straight” pathway. The glycolytic pathway is a series of enzymes catalyzed reactions which breaks down glucose into pyruvate with the concomitant release of energy (in form of ATP). read more
If step 5 is used twice per glucose, then a total of 4 ATP are made in this manner. If the cell is anaerobic (absence of oxygen), the NADH product of reaction 5 is used as a reducing agent to reduce pyruvic acid to lactic acid at step 10. read more