Question

Distinguish between light and dark reactions

Answer 1

Hint: Light reaction dark reactions are a part of photosynthesis. Photosynthesis is the most essential process in the plant for the production of oxygen. It requires a constant source of light for the initiation of the process.

Complete answer:
Photosynthesis is the process where the light energy is converted into chemical energy. It is carried out in stages.
It has two phases:
- The first phase is a light dependent process. It is a photochemical phase of the process. It is known as light reaction.
- The second phase is a light independent process. It is known as a dark reaction.

The whole process takes place inside the chloroplast.
Light reaction - In this reaction light is essential. It involves absorption of light, hydrolysis, oxygen release and formation of ATP and NADPH. It has two types of photosystems— I and II

I absorb light at 700 nm and II absorb at 680 nm wavelength. This reaction takes place in thylakoids. When light hits on the light energy molecules it gets converted to ATP and NADPH. It releases oxygen.

Dark reaction— It is known as carbon fixing reaction. Light is not required. Sugar formation takes place here with the help of carbon dioxide and water. It takes inside the stroma. Glucose formation is seen in this process.

Light reaction	Dark reaction
Light dependent	Light independent
Photochemical reaction	Biochemical reaction
It takes place in the thylakoids	It takes place in stroma
ATP and NAPDh are formed	Glucose is formed
Oxygen is released	Carbon dioxide is utilised

Note: Photosynthesis is the process where the light energy is converted into chemical energy. It has two stages i.e. light and dark reactions. This process takes place in the chloroplast. Oxygen is released in light reaction and Carbon dioxide is utilised in dark reactions.