Cyclic photophosphorylation produces ATP alone. Phosphorylation is the mechanism by which the phosphate group is added to a compound or molecule. It occurs in all living organisms, but photophosphorylation is the type of phosphorylation that only occurs in plants and some bacteria (not in humans). After that, cyclic photophosphorylation is the process that involves cyclic electron transport, while non-cyclic photophosphorylation is the process that does not involve cyclic electron transport. The other notable difference between the two processes is that cyclic photophosphorylation only produces ATP, while non-cyclic photophosphorylation produces both ATP and NADP.

Comparative chart

What is cyclic photophosphorylation?

It is the photophosphorylation process that contains a cyclic transport of electrons, its active center for the reaction is the photosystem1 (P700), it does not involve the photosystemm2 (P680). Cyclic photophosphorylation involves photosystem1, in this process electrons travel cyclically and return to photosystem1. In this process, adenosine triphosphate (ATP) is produced, which is used by plants as an energy source, this ATP is used in the Calvin cycle. The Calvin cycle process depends directly on the presence of ATP, in case there are not enough ATP, the process does not continue. Cyclic photophosphorylation does not involve oxygen production, photolysis (water splitting) is absent in this as well. Also, this process does not produce NADP or oxygen, but it continues to produce ATP. The cyclic photophosphorylation process takes place mainly in bacteria; less is seen on plants.

It is the photophosphorylation process that does not have a cyclic transport of electrons, its active center for the reaction is the photosystemm2 (P680), but it is also involved in the photosystem1 (P700). In non-cyclic photophosphorylation. Electron transport is non-cyclical, these electrons from photosystem1 (P700) are accepted by NADP. In non-cyclic photophosphorylation, ATP and NADP are produced which are used as an energy source (NADP is a rich energy source, as 1 NADP provides energy equivalent to 3 ATP). In non-cyclic photophosphorylation, oxygen is given off as a by-product of the reaction and eventually emitted into the surrounding environment, it also has photolysis or water splitting is present. The non-cyclic photophosphorylation process is observed mainly in green plants.

Cyclic photophosphorylation vs. non-cyclic photophosphorylation

• Cyclic photophosphorylation has a cyclic electron transport, whereas non-cyclic photophosphorylation has a non-cyclic electron transport order.
• Cyclic photophosphorylation has an active center P700 while non-cyclic photophosphorylation has an active center
• Cyclic photophosphorylation involves photosystem1 only, but non-cyclic photophosphorylation involves photosystem1 and photosystem2.
• Cyclic photophosphorylation produces only ATP, but contrary to this non-cyclic photophosphorylation it produces both ATP and NADP.
• In cyclic photophosphorylation, the electron returns to photosystem1, while in non-cyclic photophosphorylation the electrons of photosystem1 are accepted by NADP.
• Cyclic photophosphorylation does not generate oxygen and does not contain water photolysis, while non-cyclic photophosphorylation removes oxygen as a by-product of the reaction and has water photolysis.
• Cyclic photophosphorylation produces ATP without producing oxygen or NADP, while non-cyclic photophosphorylation produces ATP, NADP, and oxygen.
• Cyclic photophosphorylation occurs predominantly in bacteria, while non-cyclic photophosphorylation occurs primarily in green plants.