Metabolic Pathways

Metabolic Pathways

The anabolic and catabolic reactions that occur in cells usually involve a number of different steps that must occur in a particular sequence. For example, the anaerobic phase of cellular respiration, by which glucose is converted to pyruvic acid, involves 10 separate reactions.

Since each reaction is controlled by a specific kind of enzyme, these enzymes must act in proper order. Such precision of activity suggests that the enzymes are arranged in precise ways It is believed that those responsible for aerobic respiration are located in tiny, stalked particles on the membranes (cristae) within the mitochondria, and that they are positioned in the exact sequence of the reactions. 

They control Such a sequence of enzyme-controlled reactions that leads to the production of particular products is called a metabolic pathway. Typically these pathways are interconnected so that molecules of a cenain kind of substance mav enter more than one pathway as the substance is metabolized For example, carbohydrate molecules from foods may enter catabolic pathways and be used to supply energy or they may enter anabolic pathways and be stored as glycogen or fat.