Principles of Biochemistry (2+1)

3.1.4.Intermediary metabolism

3.1.14.Intermediary metabolism

                                          

               The intermediate steps within the cells in which the nutrient molecules or foodstuffs are metabolized and converted into cellular components catalyzed by enzymes is called Intermediary metabolism.  The reaction pathways that comprise metabolism are divided into two categories.

i)  Catabolism: Pathways involved in degradation such as oxidative processes that release free energy in the form of high energy phosphates (ATP) or reducing equivalents E.g Respiratory chain  and oxidative phosphorylation.

In catabolic reactions, complex substances are broken down to simpler compounds with a concomitant release of free energy, the released free NADPH. The major nutrients such as carbohydrates, lipids and proteins are converted to common intermediate and further metabolized in a central oxidative pathway.

ii) Anabolism: Pathways involved in biosynthesis e. g. Biosynthesis of proteins, lipids etc.

Simple organic molecules such as pyruvic acid, acetyl unit or intermediate compounds of citric acid cycle serve as starting molecules for varied biosynthetic products. The energy rich molecules such as ATP or NADPH derived from catabolic reactions are utilized in the biosynthetic reactions.