Why did we review glycolysis in two phases Preparatory vs Pa

Why did we review glycolysis in two phases: Preparatory vs. Payoff? What are the major differences between these two phases? In terms of the Overall glycolytic pathway, what\'s so great about the phosphofructokinase {PFK-1} catalysed conversion of fructose 6-phosphate to fructose 1, 6-bisphophate? What do we ultimately gain via glycolysis? Under anaerobic conditions, what\'s the significant of the reduction of pyruvate to lactate? How does that ultimately allow us to keep (at least in the short term) making ATP without using oxygen?

Solution

> There are two phases of glycolysis. First is preparatory phase or also known as investment phase and second phase is payoff phase. The first stage is consist of 5 steps and second stage is consist of 5 steps. The major difference between these two phases is involvement of ATP. Preparatory phase is the stage where consumption of ATP occurs, thatswhy it is also known as investment phase. The payoff phase is characterized by the release of ATP.

> Phospofructokinase is the pacemaker. Conversion of glusose 6 phosphate to glucose 1,6 biphospate through enzyme phosphofructokinase is the first irreversible reaction unique to the glycolytic pathway (since glucose 6 phosphate is not solely a glycolytic intermediate, it can be converted into glycogen or can be oxidized by pentose phosphate pathway). Thus, it is commited step and highly appropriate for phosphofructokinase to be primary control site in glcolysis.

> The ultimate gain via glycolysis are: Two molecules of ATP (although four molecules of ATP are produced during glycolysis but two ATP molecules are consumed in preparatory phase), two pyruvate molecules and two molecules of NADH.