As a result, proton concentration is increased inside the thylakoid lumen. These protons move across the membrane because the primary acceptor of electron is located outside the membrane. Protons in stroma less in number and creates a proton gradient. This gradient is broken down due to the movement of proton across the membrane to the stroma through CF O of the ATP synthase enzyme.
The proton motive force created inside the lumen of thylakoid or chemical gradient of H ion across the membrane stimulates ATP generation (Figure . ). Table . Differences between Cyclic Photophosphorylation and Non-Cyclic Photophosphorylation Cyclic Photophosphorylation Non-Cyclic Photophosphorylation .
PS I only involved . PS I and PS II involved . Reaction centre is P700 . Reaction centre is P680 .
Electrons released are cycled back . Electron released are not cycled back . Photolysis of water does not take place . Photolysis of water takes place .
Only ATP synthesized . ATP and NADPH H are synthesized . Phosphorylation takes place at two places . Phosphorylation takes place at only one place .
It does not require an external electron donor . Requires external electron donor like H O or H S . It is not sensitive to di chloro di methyl urea (DCMU) . It is sensitive to DCMU and inhibits electron flow PS II PS I Cytochromes b & f ATP Synthase + H + H + H + H + H + H + H ADP ATP + NADP + NADPH+H N E M U L Thylakoid membrane STROMA Figure .
: Chemiosmotic Theory with the help of RUBP carboxylase oxygenase (RUBISCO) enzyme accepts one molecule of carbon dioxide to form an unstable carbon compound. This 6C compound is broken down into two molecules of -carbon compound phospho glyceric acid (PGA) (Figure . ). RUBP CO Rubisco molecules PGA M.
Melvin Calvin, A.A. Benson and their co-workers in the year found this path way of carbon fixation. Melvin Calvin was awarded Nobel Prize for this in and this