LIGHT AND DARK REACTION.pptx

photosynthesis is defined as the process of making food in the presence of light water and Carbondioxide
The process of photosynthesis can be completed in two steps
a. light reaction/Hill's reaction
b. dark reaction/ Calvin Cycle

In light reaction , the light is used to make the assimilatory powers i.e., Formation of ATP and NADPH

In dark reaction, the assimilatory powers are used to fix the Co2 & making of glucose which is the food for the plants

1. WELCOME TO ALL OF YOU FOR TODAY’S PRESENTATION BACHELORS OF SCEINCE 3 RD YEAR SUBJECT: BOTANY TOPIC: LIGHT REACTION AND DARK REACTION CREATED AND PRESENTED BY: ATIF ALI ZAKIR

2. THE PROCESS OF PHOTOSYNTHESIS IS COMPLICATED ,OXIDATION REDUCTION PROCESS RESULTING IN THE OXIDATION OF WATER AND REDUCTION OF CO2 THE MECHANISM OF PHOTOSYNTHESIS COMPLETED IN TWO PHASE LIGHT REACTION / HILL’S REACTION DARK REACTION / BLACKMAN’S REACTION IN LIGHT REACTION ASSILIMATORY POWER IS GENERATE i.e ,( NADPH + H+ve +ATP ) IS GENERATED AND O2 IS RELEASED AND THE ASSILIMATORY POWER IS UTILISED IN DARK REACTION IN REDUCING OF CO2 TO CARBOHYDRATES H2O IS ELECTRON DONOR IN PHOTOSYNTHESIS MECHANISM OF PHOTOSYNTHESIS

3. LIGHT REACTION OR HILL’S REACTION IT CAN BE COMPLETED IN FIVE STEPS

4. DIFFERENT PIGMENTS ABSORBS DIFFERENT WAVELENGTHS OF VISIBLE LIGHT B. TRANSFER OF LIGHT ENERGY FROM ACESSORY PIGMENTS TO CHL-A A. ABSORPTION OF LIGHT BY CHLOROPLAST PIGMENT

5. C. ACTIVATION OF CHL-A MOLECULE BY PHOTONS OF LIGHT D. PHOTOLYSIS OF WATER AND EVOLUTION OF O2 2H2O ---LIGHT--- 4H+ + 4OH- RECOMBINE IN THE PRESENCE OF Mn , Cl ---------4e- + O2 + 2H2O

6. E. ELECTRON TRANSPORT & PRODUCTION OF NADPH+H + & ATP

7. CYCLIC P.P.R IT INVOLVES ONLY PS-I (P700) ELECTRON EMITTED CYCLED BACK TO PS-I NO NADP FORMATION TAKES PLACE ATP FORMATION FROM ADP TAKES PLACE NO O2 RELEASE DUE TO NO PHOTOLYSIS OF H20 NO NADPH2 FORMED THIS FULFIL THE REQUIREMENT OF NON CYCLIC PPR NON CYCLIC P.P.R IT INVOLVES BOTH PS-I & PS-II ELECTRON EMITTED DOSE NOT RETURN BACK TO SAME CHL. MOLECULE NADP IS FORMED & THEN REDUCE INTO NADPH2 ELECTRONS COME FROM THE SOURCE OF H2O O 2 IS RELEASED , BOTH ATP & NADPH2 FORMED PHOTOPHOSPHORYLATION A PROCESS BY WHICH LIGHT ENERGY IS TRANSFORMED INTO CHEMICAL ENERGY IN THE FORM OF ATP IS CALLED AS PHOTOPHOSPHORYLATION IT CAN BE DONE THROUGH CYCLIC OR NON CYCLIC ELECTRON TRANSPORT SYSTEM PPR IS OF TWO TYPES (CYCLIC PPR & NON CYCLIC PPR ) IN NATURE BOTH PROCESSES OF PPR PROCEEDS SIMULTANOUSLY

8. CYCLIC PHOTO - PHOSPHORYLATION

9. NON CYCLIC PHOTO-PHOSPHORYLATION NADP + 2ADP + 2Pi + 4H2O ----- LIGHT- -----NADPH2 + 2ATP + O2 + 2H2O

10. IT IS THE SECOND PHASE OF PHOTOSYNTHESIS IT TAKES PLACE IN STROMA REGION OF CHLOROPLAST LIGHT IS NOT NECESSARY FOR THIS PROCESS,HENCE CALLED AS LIGHT INDEPENDENT REACTION HERE THE REDUCTION OF CO2 INTO CARBOHYDRATES TAKES PLACE BY USING ASSILIMATORY POWERS ATP & NADPH2 GENERATED DURING LIGHT RXN IT INVOLVES SERIES OF ENZYMATIC REACTION WHICH OCCURS IN CYCLE & IS ALSO CALLED AS CALVIN CYCLE AFTER THE NAME OF SCIENTIST CALVIN MELVIN THIS CYCLE CAN BE COMPLETED IN THREE PHASES CARBOXYLATION PHASE REDUCTION PHASE REGENRATION PHASE DARK REACTION/CALVIN CYCLE OR C3 CYCLE /PHOTOSYNTHETIC CARBON REDUCTION CYCLE

11. DARK REACTION/ CALVIN CYCLE

12. IN CARBOXYLATION PHASE ,ADDITION OF CO2 TO FIVE CARBON COMPOUND i.e ., RIBULOSE 1,5-BISPHOSPHATE ( RUBP ,PRIMARY ACCEPTOR) IN THE PRESENCE OF ENZYME RUBISCO THIS RESULT IN THE FORMATION OF TWO MOLECULES OF 3-PHOSPHOGLYCERATE (3-PGA & 3 Carbon Compound) CO2 + RUBP -----RUBISCO----- 3-PHOSPHOGLYCERATE (2 mol.) RUBISCO IS THE PACEMAKER ENZYME OF THE CALVIN CYCLE & IS MOST ABUNDANT IN CHLOROPLAST 3-PHOSPHOGLYCERATE IS THE FIRST STABLE PRODUCT OF DARK RXN HENCE CALLED AS C3 -CYCLE IT DOSE NOT REQUIRE ANY ATP & NADPH MOLECULE IN ALL MOLECULES OF CO2 REACT WITH 6 RUBP FORMING 12 MOLECULES OF 3-PHOSPHOGLYCERATE (3-PGA) A. CARBOXYALTION PHASE

13. THIS STEP INVOLVES THE REDUCTION OF 2 mol. OF 3PGA TO 3-PHOSPHOGLYCERICERATE TO 3- PHOSPHOGLYCERALDEHYDE IN THE PRESENCE OF ENZYME PGA KINASE HERE ONE MOLECULE OF G3P GOES TO MAKE GLUCOSE AND THE REMAINING 5C- COMPOUND ENTERS IN THE REGENERATION PHASE HERE TWO MOLECULES OF ATPs AND NADPH2 B. REDUCTION PHASE

14. IN THIS PHASE THE REGENERATION OF RUBP TAKES PLACE AFTER REPIDLY SIX CYCLES SIX MOLECULES OF GLYCERALDEHYDE -3-PHOSPHATE FORMED IN 6 CALVIN CYCLES FOR REGENERATION OF ONE 5C COMPOUND OF RUBP MOLECULE ,ONE MOLECULE OF ATP IS USED HENCE ,THE TOTAL 18 ATPs & 12 NADPH2 MOLECULES ARE REQUIRED FOR SYNTHESIS OF ONE GLUCOSE MOLECULE C . REGENERATION PHASE

15. CO2+H2O+ LIGHT---- GIVES---- C6 H12 O6+O2 THE FIXATION AND REDUCTION OF ONE MOLECULE OF CO2 REQUIRES THREE MOLECULES OF ATPS TWO MOLECULES OF NADPH2 COMING FROM THE LIGHT RXN FOR EVERY SIX MOLECULES OF 3PGA PRODUCED AT THE EXPENSE OF 18 ATPS, 12NADPH2 AND 6 CO2 ONLY ONE MOLECULE OF CARBON ENTERS THE METABOLIC POOL AS A NET GAIN IN ENERGY AND THE FIVE REMAINING MOLECULES FORMS RUBP WHICH ACCEPT AGAIN CO2 TO INITIATE C3 CYCLE BALANCE SHEET

16. THANK YOU SO MUCH FOR ATTENDING TODAY’S PRESENTATION CREATED AND PRESENTED BY ATIF ALI ZAKIR STUDENT OF MSC BOTANY II YEAR SAIFIA SCIENCE COLLEGE BHOPAL