Oxidative phosphorylation Animation - Formation of ATP & sites of ATP synthesis

Introduction

In oxidative phosphorylation, the process of ATP formation and the sites of ATP synthesis during the transfer of electrons through the electron transport chain are discussed. Energy produced during electron transfer is coupled to ATP formation by phosphorylation of ADP by an enzyme called ATP synthase. This process is known as oxidative phosphorylation, and there are three ATP synthesizing sites in the electron transport chain. These sites are responsible for the production of ATP molecules by utilizing the energy derived from the oxidation of reducing equivalents. The mechanism of oxidative phosphorylation is explained by the chemiosmotic theory, which describes the coupling of oxidation and phosphorylation by a proton gradient across the mitochondrial membrane.

The structure and function of the ATP synthase complex, which is essential for ATP synthesis, are detailed. The ATP synthase complex consists of two subunits - F0 and F1. The F0 subunit is hydrophobic and spans the inner mitochondrial membrane, while the F1 subunit is hydrophilic and exposed to the mitochondrial matrix. The flow of protons through the F0 subunit causes the rotation of the complex along with the gamma subunit of the F1 complex, leading to ATP production. This process is likened to a rotor-stator molecular motor due to the rotating and stationary subunits within the ATP synthase complex.

The tight coupling of electron flow and ATP synthesis, known as respiratory control, ensures that oxygen consumption is dependent on the availability of ADP. A new theory called the binding change mechanism, proposed by Paul Boyer, explains the ATP production in the beta subunit of the F1 complex. This mechanism involves the re-entry of protons through the F0 subunit, causing rotation of the gamma subunit and subsequent conformational changes in the beta subunits of the F1 complex.

Keywords

Oxidative phosphorylation, ATP synthesis, Electron transport chain, Chemiosmotic theory, ATP synthase complex, Respiratory control, Binding change mechanism

FAQ

1. What is oxidative phosphorylation?

   • Oxidative phosphorylation is the process of ATP formation during electron transfer through the electron transport chain, coupled with the oxidation of reducing equivalents.

2. What are the sites of ATP synthesis in the electron transport chain?

   • There are three ATP synthesizing sites: complex 1 (between NAD and Coenzyme Q), complex 3 (between Coenzyme Q and cytochrome C), and complex 4 (between cytochrome C and oxygen).

3. How does the ATP synthase complex function in ATP production?

   • The ATP synthase complex consists of rotating (F0 and gamma subunit) and stationary (F1 complex) subunits, where the flow of protons through F0 causes rotation, leading to ATP synthesis in the F1 complex.

4. What is respiratory control in oxidative phosphorylation?

   • Respiratory control is the tight coupling of electron flow and ATP synthesis, ensuring that oxygen consumption is regulated by the availability of ADP.