Question

ATP synthase requires an energy source to synthesize ATP.

Tell me what the source of energy is and why energy is required for this process.

Answer 1

In electron transport chain, five complex are present. Among the complex, complex V is known as ATP synthase complex. It is made up of two units Fo , and F1 ATP synthase.

Fo act as ion channel , prsent in mitochondria membrane and allow entry of ions .

F1 attached to Fo and located in to mitochondria matrix. And carry put ATP synthesis.

Main energy required for synthesis of ATP is proton gradient formed by electron transport chain. In metabolic pathway reducing equivalent ( NADH and FADH2).are produced. These enter in to ETC, in ETC as electron are passed to electron transport chain energy is released . At some complexs ( I, III and IV)  the released energy is enough to transport H ion across mitochondria membrane. This lead to accumulation of H+ ion in intermembrane space and generate protin motive force ( PMF). This PMF act as energy source to carry out ATP synthesis. As H+ ion enters through F0 complex, energy is released and used to carry out ATP synthesis.  

Incomplex V ,F1 subunit is made of 9 subunit ( 3 alpha, 3 beta , 1 gamma, 1 sigma and 1 epsilon) . Among these beta subunit is active part which carry out ATP synthesis. It exists in 3 conformation open, loose and tight. For inter conversion of these 3 forms energy is required which is provided by proton gradient. As proton gradient released, this energy is used to carry out inter conversion of these forms and lead to synthesis of ATP.