Final answer:
In Stage II of glycolysis under cellular conditions, two enzymes catalyze irreversible reactions: phosphofructokinase and pyruvate kinase.
Step-by-step explanation:
In Stage II of glycolysis under cellular conditions, there are two enzymes that catalyze irreversible reactions. These enzymes are phosphofructokinase and pyruvate kinase.
Phosphofructokinase catalyzes the conversion of fructose-6-phosphate (F-6-P) to fructose-1,6-bisphosphate (F-1,6-BP). This reaction is irreversible because it is highly exergonic and regulated by allosteric control. The formation of F-1,6-BP is a key regulatory step in glycolysis.
Pyruvate kinase catalyzes the conversion of phosphoenolpyruvate (PEP) to pyruvate, resulting in the production of ATP. This reaction is also highly exergonic and irreversible. So therefore in stage II of glycolysis under cellular conditions, two enzymes catalyze irreversible reactions are phosphofructokinase and pyruvate kinase.