Q. The process of photophosphorylation was discovered by
NTA AbhyasNTA Abhyas 2020
Solution:
The light phase includes the interaction of two pigment systems. PS I and PS II constitute various types of pigments. Arnon and his co-workers showed that during light reaction not only reduced NADP is formed and oxygen is evolved but ATP is also formed. This formation of high energy phosphates (ATP) is dependent on light hence called photophosphorylation. It is of following two types-
- Cyclic photophosphorylation: It involves only PS I. Flow of the electron is cyclic. When NADP is not available, or the CO2 concentration is very low in the atmosphere leading to the accumulation of NADPH2, then this process will occur.
- Noncyclic photophosphorylation: It involves both PS-I and PS-II. The flow of the electron is unidirectional. Here electrons are not cycled back and are used in the reduction of NADP to NADPH2.
- Cyclic photophosphorylation: It involves only PS I. Flow of the electron is cyclic. When NADP is not available, or the CO2 concentration is very low in the atmosphere leading to the accumulation of NADPH2, then this process will occur.
- Noncyclic photophosphorylation: It involves both PS-I and PS-II. The flow of the electron is unidirectional. Here electrons are not cycled back and are used in the reduction of NADP to NADPH2.