Question

Oxidative phosphorylation refers to
A. Anaerobic production of ATP.
B. Citric acid cycle production of ATP
C. Production of ATP by chemiosmosis.
D. Alcoholic fermentation

Answer 1

Hint: Oxidative phosphorylation takes place in the mitochondria which depends upon the electron transport. There is a proton gradient that helps in the synthesis of ATP. We know that cellular respiration is primarily governed by the need for ATP.

Complete answer:
NADH and $FADH_2$ that are formed in glycolysis, fatty acid oxidation contains a pair of electrons having a high transfer potential. When these electrons are used to reduce molecular oxygen into water, a large amount of energy is given out that is used to generate ATP. Oxidative phosphorylation refers to the process of synthesis of ATP by the proton motive force that is developed during the oxidation of reducing power NADH and $FADH_2$ through electron transport chain.
It takes place in mitochondria, which is the major source of ATP production in aerobic organisms. The uses of proton motive force drive transport of proton down the concentration gradient and later ATP phosphorylation represents chemiosmosis.
It takes place in a series of energy transformations that are called cellular respiration. The carbon fuels are oxidized in citric acid to yield electrons of high potential. This electron is then converted into proton - motive force and then finally gets converted into phosphoryl transfer potential. There are three electron driven proton pumps NADH-Q oxidoreductase, Q-cytochrome c oxidoreductase, Q and cytochromes c oxidase that are responsible for conversion of electron motive force into proton motive force. There are many oxidation reduction centers in these large transmembrane complexes including hemes, falvins, iron- sulphur clusters,quinones and copper ions. The final phase is carried out by ATP synthesis that is driven by the flow of protons back into the mitochondrial matrix. Oxidative phosphorylation reveals that proton gradients are an interconvertible currency of free energy in the system.

Note-
Both ATP synthesis and electron transport chain are embedded in the mitochondria and the energy is transferred from the electron transport chain of the ATP synthases by movement of protons across the mitochondrial membrane by the process of chemiosmosis. Peter Mitchell in 1961 put forward this process in ETC. He got the Nobel prize in 1978 for this hypothesis.