Question

Chemiosmotic coupling hypothesis of oxidative phosphorylation propose ATP synthesis because of
(a)proton gradient forms across the inner membrane.
(b)changed the impermeability of the inner mitochondrial membrane to ADP.
(c)high energy bonds are formed in mitochondrial proteins.
(d)ADP is pumped out of the matrix into intermembrane space.

Answer 1

Hint: Chemiosmotic phosphorylation is the third pathway that produces ATP from inorganic phosphate and an ADP molecule. This process is a part of oxidative phosphorylation.

Complete answer:
The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes ATP synthesis because of proton gradient forms across the inner membrane. The process of oxidative phosphorylation occurs inside mitochondria with the help of electron transporters located in the inner mitochondrial membrane. During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors such as oxygen in redox reactions. These redox reactions release the energy stored in the relatively weak double bond of ${ O }_{ 2 }$, which is used to form ATP. The flow of electrons in the mitochondrial electron transport system is coupled with the outflow of protons to the peri-mitochondrial space. This will form potential energy in the form of a pH gradient and an electrical potential across this membrane. The accumulation of protons in the peri-mitochondrial space establishes an electrochemical gradient as well as the chemical gradient. The accumulated protons, later on, flow along this electrochemical gradient.​
This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient, through a large enzyme called ATP synthase; this process is known as chemiosmosis. The ATP synthase uses the energy to transform adenosine diphosphate (ADP) into adenosine triphosphate, in a phosphorylation reaction. ATP synthase enzyme complex is present on the inner mitochondrial membrane when ATP is synthesized.
So, the correct answer is, ‘proton gradient forms across the inner membrane’.

Note: -The energy transferred by electrons flowing through the electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport.
- In eukaryotes, these redox reactions are catalyzed by a series of protein complexes within the inner membrane of the cell's mitochondria.