what is the significance of the substrate level phosphorylation?

Answer 1

In respiration the production of ATP is paramount. The best and most efficient way to produce ATP is by oxidative phosphorylation. The main problem is that in order for this to continuously occur you need a constant supply of oxygen. Sometimes the cells, organism cannot get the oxygen it needs and must use an alternative way to release energy. This is where fermentation occurs. Glycolysis uses substrate level phosphorylation in its production of ATP, NADH and pyruvate. The NADH and pyruvate contain the bulk of the energy to produce additional ATP's if oxygen is present. When oxygen is not present the process of fermentation occurs. The cell needs alternate ways of producing ATP when it is under respiratory stress. It seems that this is a carry over from when there was very little or no atmospheric oxygen avaliable to life . What ever the reason it helps us out.

Answer 2

It refers to the direct addition of a phosphate group to a compound by using a high-energy compound as the donor. In most cases people are referring too the formation of ATP from ATP (as in glycolysis), but it could apply to and compound being phosphorylated. In the case of ATP formation it is useful to distinguish between this and oxidative phosphorylation .