Give comparison between the following: Cyclic and non-cydic photophosphorylation

Cyclic and non-cyclic photophosphorylation are two processes involved in the light-dependent reactions of photosynthesis. Here's a comparison between the two:

1. Definition:

   • Cyclic Photophosphorylation: Cyclic photophosphorylation is a process in which electrons flow through only one photosystem (usually photosystem I) and return to the same photosystem, resulting in the production of ATP without the release of oxygen.
   • Non-cyclic Photophosphorylation: Non-cyclic photophosphorylation is a process in which electrons flow through both photosystem I and photosystem II, leading to the production of both ATP and NADPH, as well as the release of oxygen.

2. Photosystems Involved:

   • Cyclic Photophosphorylation: Only photosystem I is involved in cyclic photophosphorylation.
   • Non-cyclic Photophosphorylation: Both photosystem I and photosystem II are involved in non-cyclic photophosphorylation.

3. Electron Flow:

   • Cyclic Photophosphorylation: Electrons extracted from chlorophyll molecules in photosystem I are passed through a series of electron carriers and eventually return to chlorophyll, completing a cyclic pathway. As electrons move through the carriers, they generate a proton gradient across the thylakoid membrane, driving ATP synthesis via ATP synthase.
   • Non-cyclic Photophosphorylation: Electrons extracted from water molecules are initially passed through photosystem II, where they are energized by light and then passed through an electron transport chain to photosystem I. In photosystem I, electrons are re-energized by another photon of light and ultimately used to reduce NADP+ to NADPH. The flow of electrons through both photosystems generates a proton gradient across the thylakoid membrane, driving ATP synthesis via ATP synthase in addition to the production of NADPH.

4. Product Formation:

   • Cyclic Photophosphorylation: The main product of cyclic photophosphorylation is ATP. No NADPH or oxygen is produced.
   • Non-cyclic Photophosphorylation: The products of non-cyclic photophosphorylation are ATP, NADPH, and oxygen. Oxygen is produced as a byproduct of the splitting of water molecules in photosystem II.

5. Function:

   • Cyclic Photophosphorylation: Cyclic photophosphorylation primarily functions to generate ATP for the light-independent reactions (Calvin cycle) of photosynthesis.
   • Non-cyclic Photophosphorylation: Non-cyclic photophosphorylation functions to generate both ATP and NADPH, which are utilized in the Calvin cycle to fix carbon dioxide and produce organic molecules.

In summary, both cyclic and non-cyclic photophosphorylation are processes involved in the generation of ATP during the light-dependent reactions of photosynthesis. However, they differ in the photosystems involved, electron flow pathways, products formed, and overall functions within the photosynthetic process.