13. Respiratory chain – localization, function and molecular structure. Oxidative phosphorylation coefficient (P/O). Respiratory control, phosphate potential. Inhibitors of the electron transport. Chemiosmotic theory of the mechanism of oxidative phosphorylation in the respiratory chain. ATP synthase. Effect of uncoupling agents and inhibitors of the oxidative phosphorylation.

INTRODUCTION TO THE RESPIRATORY CHAIN

• The respiratory chain, also known as the electron transport chain, is a crucial component of cellular respiration, the process by which cells generate energy in the form of adenosine triphosphate (ATP). Located in the inner membrane of mitochondria, the powerhouse of the cell, this chain is the final and most complex stage of metabolism in aerobic organisms.

Fundamental Role

• The primary role of the respiratory chain is to convert the energy stored in reduced metabolic intermediates (NADH and FADH2) into ATP, which is used as a universal energy currency by cells to perform various functions. This process involves a series of redox reactions where electrons are transferred through a sequence of protein complexes and mobile carriers within the mitochondrial inner membrane.

MECHANISM OF ACTION

As electrons move through the chain, they release energy at key steps. This energy is harnessed to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating an electrochemical gradient known as the proton motive force.

The return flow of protons into the matrix through ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate.