Question

Theory of chemiosmosis was propounded by

• A. Mitchell
• B. Kok
• C. Arnold
• D. Calvin

Answer 1

Answer: (A)

Mitchell

The mechanism of ATP synthesis in photosynthesis has been explained by Mitchell in 1961, called the chemiosmotic hypothesis.

According to this hypothesis, the ATP synthesis is linked to the development of a proton gradient across the thylakoid membrane. The actual site of ATP synthesis is ATPase complex located on the non-appressed portions of thylakoid membranes. During photosynthesis electron transport, protons accumulate in thylakoid space. Increase in protons in the thylakoid space causes the pH of one side of the membrane to decrease.

At the same time, the pH of the thylakoid membrane towards the stroma side increases due to the utilization of protons. This difference in hydrogen concentration on two sides of the thylakoid membrane leads to the building of a transmembrane proton concentration gradient which acts as the driving force behind the conversion of ADP into ATP.

Thus, the correct answer is option A.