Non-cyclic and Cyclic Phosphorylation in Photosynthesis

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll. The process involves two stages: the light reactions and the dark reactions. The light reactions take place in the thylakoid membranes of the chloroplasts and involve the conversion of light energy into chemical energy. Within the light reactions, there are two types of phosphorylation: non-cyclic and cyclic phosphorylation.

Non-Cyclic Phosphorylation

Non-cyclic phosphorylation is also called Z-scheme or electron transport chain. In this process, the electrons released during the photoexcitation of the chlorophyll molecules are passed through a series of electron carriers, which are embedded in the thylakoid membranes. The electron carriers are arranged in order of their redox potentials, and the electrons are passed from one carrier to another, releasing energy in the form of ATP and NADPH.

The process of non-cyclic phosphorylation can be broken down into the following steps:

1. Photoexcitation of chlorophyll molecules: Chlorophyll molecules in the thylakoid membranes are excited by photons of light.

2. Electron transfer: The excited electrons are transferred to the primary electron acceptor, which is located in the reaction center of the photosystem.

3. Electron transport: The electrons are then passed through a series of electron carriers, which are embedded in the thylakoid membranes.

4. ATP synthesis: As the electrons pass through the electron carriers, they release energy, which is used to synthesize ATP.

5. NADPH synthesis: The electrons are finally transferred to NADP+ to form NADPH.

Cyclic Phosphorylation

Cyclic phosphorylation is a type of photophosphorylation that occurs in the thylakoid membranes of the chloroplasts. In this process, the electrons released during the photoexcitation of the chlorophyll molecules are passed through a cyclic electron pathway, which produces ATP but not NADPH.

The process of cyclic phosphorylation can be broken down into the following steps:

1. Photoexcitation of chlorophyll molecules: Chlorophyll molecules in the thylakoid membranes are excited by photons of light.

2. Electron transfer: The excited electrons are transferred to the primary electron acceptor, which is located in the reaction center of the photosystem.

3. Electron transport: The electrons are then passed through a series of electron carriers, which are embedded in the thylakoid membranes.

4. ATP synthesis: As the electrons pass through the electron carriers, they release energy, which is used to synthesize ATP.

Short Tricks: Photosynthesis in Higher Plants - 1

1. Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

2. The process involves two stages: the light reactions and the dark reactions.

3. Within the light reactions, there are two types of phosphorylation: non-cyclic and cyclic phosphorylation.

4. Non-cyclic phosphorylation involves the conversion of light energy into chemical energy, producing ATP and NADPH.

5. Cyclic phosphorylation produces ATP but not NADPH.

6. Non-cyclic phosphorylation is also called Z-scheme or electron transport chain.

7. Cyclic phosphorylation occurs in the thylakoid