Question

Explain briefly photolysis.

Answer 1

Hint: Photo is used to refer, using or producing by light and lysis refers to the disintegration of a substance, molecules, cells, etc. A process involving light is always referred to with a suffix ‘photo’ example, photolysis, photosynthesis, etc.

Complete answer:
-Photolysis is a chemical process involving light to break down molecules into smaller units. It involves a chemical reaction that breaks down an organic or inorganic chemical into a photon and requires the interaction of one or more photons with one target molecule.
-Photolysis usually occurs during photosynthesis, where water molecules into hydrogen and oxygen in the presence of sunlight. This process is known as Photolysis of water. Here the photons absorbed by the plant cause the hydrogen to release oxygen and bind to a hydrogen acceptor like a coenzyme NADP to form NADPH. This NADPH is then transferred along with ATP to the Calvin cycle site.
-Oxygen is the by-product also known as a waste product of photolysis that is released in the environment and is taken up by other living organisms like humans for their survival.
-Photolysis of water reaction is as follows:
$2{ H }_{ 2 }O\quad +\quad 2NAD{ P }^{ + }\quad +\quad 8photons\left( Light \right) \quad →\quad 2NADPH\quad +\quad 2{ H }^{ + }\quad +\quad { O }_{ 2 }$

Additional Information:
-Photolysis is important in processes like photosynthesis where it helps in the formation of energy currency like NADPH required by the plants.
-The very high redox potential of ${P680^+}$ is known as the driving force of Photolysis. It occurs in the granum of a chloroplast where chlorophyll absorbs the light.

Note:
Chemical processes that use light usually involve a photochemical reaction. Photolysis is one such chemical process which is also known as photodissociation and photodecomposition. Phototrophs are the organism that depends on light for their survival such as plants and blue-green algae.