Question

The Chemiosmotic Theory of ATP synthesis in the chloroplasts and mitochondria is based on
A. Proton Gradient
B. Accumulation of \[K^+\] ions
C. Accumulation of \[Na^+\] ions
D. Membrane potential

Answer 1

Hint: The chemiosmotic theory or the Chemiosmotic hypothesis was proposed by Peter Mitchell. The hypothesis states that a proton- motive force was responsible for driving the ATP synthesis. It occurs in specialized cell organelles such as chloroplasts and mitochondria, which are involved in respiration or ATP synthesis.

Complete answer: During the process of electron transport chain (ETC) which results in the ATP generation. There forms a proton gradient especially in the inner membrane of the mitochondria and this gradient caused by the protons is the major force that is involved in the synthesis of ATP molecules. This happens due to the breaking down of molecules such as glucose which are very rich in energy. The protons are moved across the inner membrane through the enzyme ATP Synthase. It is an energy-producing mechanism in many bacteria.
Considering the other options:
-Accumulation of \[K^+\] ions and its transport is involved mostly in the transportation of nutrients, the ions are also involved in maintaining the membrane potential in neurons, for conduction of the action potential, but is not involved in the chemiosmotic theory.
-Accumulation of \[Na^+\] ions is also involved in impulse conduction. But not in chemiosmosis.
-The membrane potential is the potential difference between the outer and inner membrane surfaces of any cell. It is mostly present in cells involved in conduction, such as neurons or muscle cells.
Thus, the most appropriate answer is A, i.e., the chemiosmotic theory is based on the proton gradient.

Note: Chemiosmosis is a process by which ions are moving across a semipermeable membrane of a structure. The movement occurs down the electrochemical gradient. This occurs during respiration in the cell and also during photosynthesis.