Question

list at least three reasons why metabolic pathways are irreversible. Can the substrate in the initial step be regenerated?

Answer 1

Metabolic reactions with large, negative ?G are said to be irreversible. Thermodynamically speaking, irreversible reactions drive metabolic pathways forward.

Enzymes catalyzing metaabolic reactions essentially irreversible reactions are potential sites of control. For example, glycolysis, the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase are virtually irreversible; hence, these enzymes would be expected to have regulatory as well as catalytic roles.

a. Allosteric inhibition

b. Feedback inhibition

c. Covalent modification these 3 control enzyme activity ghere by metabolic reaction