Regulation of Aerobic Respiration

Identify if each of the following statements about metabolism is True or False.

1. Allosteric regulators can either increase or decrease the activity of an enzyme.

True

2. Feedback inhibitors should go back as far as possible in a pathway without inhibiting a reaction that will produce a necessary product for another pathway.

False

3. ADP is a positive regulator of phosphofructokinase.

True

4.  ATP is a positive regulator of phosphofructokinase. False

Phosphofructokinase (PFK) is a glycolytic enzyme that catalyzes the irreversible transfer of a phosphate from ATP to fructose-6-phosphate:

fructose-6-phosphate + ATP fructose-1,6-bisphosphate + ADP

In part because of the irreversible nature of this step in glycolysis, PFK is the key regulatory enzyme for glycolysis. When ATP levels are high in the cell, the cell no longer needs metabolic energy production to occur. In this case, PFK's activity is inhibited by allosteric regulation by ATP itself, closing the valve on the flow of carbohydrates through glycolysis.