Cyclic and non cyclic photophosphorilation

Cyclic and non cyclic photophosphorilation

1. Cyclic And Non-Cyclic Photophosphorilation BIOSCIENCE FOR NANOTECHNOLOGY

2. OVERVIEW OF PHOTOSYNTHESIS A process by which autotrophic organisms use light energy (sunlight) to make sugar & oxygen gas from carbon dioxide & water.

3. light oxygen carbon dioxide carbohydrates water

4. PHOTOSYNTHESIS PROCESS LIGHT REACTIONS DARK REACTIONS No light needed. I nstead, dark reactions use ATP and NADPH to produce energy molecule. Light needed to produce organic energy molecules ATP and NADPH.

5. PHOTOPHOSPHORYLATION The synthesis of ATP from ADP and inorganic phosphate in presence of light is known as photophosphorylation.

6. TYPES OF PHOTOPHOSPHORYLATION NON – CYCLIC PHOTOPHOSPHORYLATION CYCLIC PHOTOPHOSPHORYLATION 01 02

7. PIGMENTS INVOLVED • There are many pigments involved – Chlorophyll - Chlorophyll a, b, c, d, Bacteroid chlorophyll, Bacterioviridin . Carotenoids - Xanthophylls and Carotene. Phycobilin – Phycocyanin and Phycoerythrin •Chlorophyll a = reaction centre •Other pigments = Accessory pigments

8. SITE OF PHOTOSYNTHESIS Chloroplast - found in mesophyll cells of leaves The photosynthesis takes place in chloroplast. Chlorophyll pigments are present in thylakoids. The thylakoids are arranged in stacks like the piles of coins called grana Stroma lamellae connect granum to each other and also to inner membrane of chloroplast. The cytoplasm of the chloroplast is called stroma. The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins.

9. Photosystem Photosystems are pigments that are organized in the thylakoid membrane in to two different photosystems (PS I & PS II ) Each PS has one specific chlorophyll – a, and many other accessory pigments bound by proteins. Chlorophyll – a forms the reaction center (actual reaction takes place) other pigments form the light harvesting complex (LHC) called antennae which gather light and transfer it to reaction center. PS I reaction center is P700 (chlorophyll –a absorbs light at 700 nm) PS II reaction center is P680 (chlorophyll –a absorbs light at 680 nm)

10. PHOTOPHOSPHORYLATION NON-CYCLIC

11. NON – CYCLIC PHOTOPHOSPHORYLATION

12. NON- CYCLIC PHOTOPHOSPHORYLATION Plants and cyanobacteria utilize two photosystems which work sequentially to produce both energy and reducing power. First, a photon of light ejects a high electron from photosystem II. The electron lost from photosystem II does not return to photosystem II, but is replaced by an electron generated from the enzymatic splitting of water and the release of oxygen. The electron then travels from the excited reaction center of photosystem II down an electron transport chain and finally to the reaction center of photosystem I. This transport system produces ATP. Since the excited electron does not return to photosystem II, this mechanism for making ATP is called non-cyclic photophosphorylation. OVERALL RESULT OF Z-SCHEME. The result of the non-cyclic electron flow is that water is oxidized yielding H + , e - and O 2 . ATP is produced. NADP + becomes NADPH2. The hydrogen and Energy of NADPH2 and ATP produced in the light reaction are used in dark reaction. PQ - Plastoquinone PC - Plastocyanin

13. PHOTOPHOSPHORYLATION CYCLIC

14. CYCLIC PHOTOPHOSPHORYLATION

15. CYCLIC When an electron is energized by absorption of light, it is ejected from the photosystem reaction center. The electron then passes down through an electron transport system, and finally to the reaction center. The energy released during this electron transport is used to produce ATP. Since the excited electron returns to the reaction center, this mechanism for making ATP is called cyclic photophosphorylation. PHOTOPHOSPHORYLATION

16.   PHOTOSYSTEM I PHOTOSYSTEM II Reaction center P700 Chlorophyll a (absorb 700nm) P680 Chlorophyll a (absorb 680nm) Cycling Involves in both cyclic and non-cyclic photophosphorylation Involved only in non-cyclic photophosphorylation Location Non-cyclic: Outer surface of thylakoid membrane Cyclic: stroma lamellae Inner surface of thylakoid membrane Photolysis Of Water Does not occur Occur Oxygen Production Does not occur Occur Formation Of NADPH Occur Does not occur Source Of Electron Non-cyclic: PS II Cyclic: Chlorophyll a From photolysis of water

17. Non-cyclic Photophosphorylation Cyclic Photophosphorylation It is associated with both PS I and PS II. It is associated with PS I. The electrons are not cycled back but compensated by the electrons from photolysis of water. The electron expelled from chlorophyll molecule is cycled back. Photolysis of water and evolution of oxygen (byproduct) take place. Photolysis of water and evolution of oxygen (byproduct) do not take place. Photophosphorylation takes place only at one place. Photophosphorylation takes place at two places. NADP + is reduced to NADPH 2 . NADP + is not reduced. ATP and NADPH 2 is synthesized. Only ATP is synthesized. H 2 O is external source of electron. No external source of electron is needed.

18. THANK YOU