How are the opposing pathways of glycolysis and gluconeogenesis prevented from extensive futile cycling?
A) At least seven of the enzymes in the two pathways are different.
B) Key enzymes are regulated in a coordinated and reciprocal manner.
C) Catabolic and anabolic pathways do not take place in the same cellular compartments.
D) The overall free-energy change always favors the catabolic pathway.
E) Gluconeogenesis involves three endergonic bypass reactions.

Question

Quizplus · Accepted Answer

Key enzymes in the opposing pathways of glycolysis and gluconeogenesis are regulated in a coordinated and reciprocal manner to prevent extensive futile cycling. For example, the enzyme pyruvate kinase is activated in glycolysis but inhibited in gluconeogenesis, while the enzyme fructose-1,6-bisphosphatase is inhibited in glycolysis but activated in gluconeogenesis. This ensures that the pathways are not simultaneously active and wasteful.

How Are the Opposing Pathways of Glycolysis and Gluconeogenesis Prevented