Question

Can organisms use both mechanisms of ATP? (Oxidative Phosphorylation and substrate-level phosphorylation)

Answer 1

yes.

two types of phosphorylations, substrate level phosphorylation and oxidative phosphorylation evolved in nature.

oxidative phosphorylation produces tremendous amount of energy in terms of ATP as compared to just substrate level phosphorylation.

For complex higher organisms, respiring aerobically, survival isn't met entirely through substrate level phosphorylation , the organism might go into sensecence and in case of humans. Humans would just die within a very short interval of time if the oxidative phosphorylation mode is cut off ( in other words if the oxygen supply is cut off since Oxygen is the last acceptor of electron in the chain and then it's coupled with ATP synthesis.)

Hence, the need for the two modes of phosphorylation.

Substrate level phosphorylation is a process that converts ADP into ATP by direct transfer of a phosphate group from a phosphorylated compound to ADP. Substrate level phosphorylation can be seen in glycolysis and Krebs cycle.Substrate level phosphorylation occurs in the cytosol and mitochondrial matrix.

Oxidative phosphorylation uses proton gradient (H+ ion concentration gradient) generated in the electron transport chain to phosphorylate ADP into ATP in aerobic organisms.Oxidative phosphorylation can be seen in electron transport chain. Oxidative phosphorylation occurs in the inner membrane of mitochondria.