Question

Define chemiosmosis.

Answer 1

The chemical reaction that occurs through a membrane semipermeable in nature particularly through a membrane in a biological cell. It is a type of osmosis. The chemiosmotic theory was proposed by Peter D. Mitchell in 1961.

Complete answer:
Osmosis: the net movement of a solvent molecule from an area of lower solute concentration through an area of higher solute concentration through a partially permeable membrane is called osmosis.
Chemiosmosis: the chemical reaction that occurs through a membrane semipermeable in nature particularly through a membrane in a biological cell is known as chemiosmosis. In this, the ions move down to their electrochemical gradient. For example, through this process, there is the formation of ATP as the hydrogen molecule moves across the membrane during respiration.
As the formation of ATP is somehow related to the process of osmosis that is why it is called chemiosmosis. The enzyme used in the formation of ATP is ATP synthase as it allows protons to phosphorylate adenosine diphosphate (ADP) by moving through the membrane and using the free energy difference, making ATP.

The chemiosmotic theory: The chemiosmotic theory was proposed by Peter D. Mitchell in 1961. the theory suggests that across the inner membranes of mitochondria, energy formed (NADH, $FAD{H_2}$) during the breaking down of molecules such as glucose are used up in the synthesis of most adenosine triphosphate (ATP) which originate from the electrochemical gradient.
The passage of ions through the membrane depends on two factors:
Diffusion force of a concentration gradient.
The electrostatic force of electrical potential gradient.

Note:
The process of chemiosmosis i.e. generation of ATP takes place in mitochondria, chloroplasts, as well as in most bacteria and archaea. In 1978 Peter Dennis Mitchell was awarded the Nobel Prize in Chemistry for the discovery of chemiosmotic theory.