BIOL 111 301 1st Edition Lecture 12 Outline of Last Lecture I Review Preview II Nature Of Light III Pigments IV What happens to the absorbed light V Light Reactions converting solar energy to chemical energy VI How much energy did we harvest from the sun Outline of Current Lecture I Review II OVERVIEW OF CALVIN CYCLE III Melvin CALVIN Cycle IV Photorespiration an evolutionary relic that causes problems V Adaptations Around This Relic Current Lecture Review o 1 Which parts of the chloroplast are we concentrating on Why o 2 Which wavelengths are absorbed by the pigments in the chloroplast o 3 What is the primary purpose of the light reactions o 4 What is the source of the electrons for the light reactions o 5 Describe electron flow during the light reactions o 6 Where is the high H concentration in a chloroplast o 7 What is the purpose of cyclic electron flow OVERVIEW OF CALVIN CYCLE o What does cycle mean o What is C input C output o What types of energy are used o Is it catabolic or anabolic o Following NET synthesis of ONE G3P o Need 3 turns of the cycle for one G3P Melvin CALVIN Cycle o PHASE 1 CARBON FIXATION 3x CO2 5 C RuBP 6 C 2 3 C Rubisco most abundant enzyme on earth o PHASE 2 REDUCTION Input ATP 6 ATP 3 cycles Input 2e 6NADPH 6NADP 3 cycles Output 1 3 C G3P o PHASE 3 REGENERATION of RuBP CO2 acceptor 5 3 C rearranged to 3 5 C RuBP Input 3 ATP 3 cycles Photorespiration an evolutionary relic that causes problems o Ancient atmosphere Before photosynthesis increased CO2 decreased O2 Cyanobacteria 1st to photosynthesize 2 7 billion years ago o Ancient atmosphere o Rubisco can bind CO2 OR O2 When o Rubisco Ribulose bisphosphate carboxylase oxygenase o Why is this a problem Releases CO2 Uses ATP in the process Decreases photosynthesis output by 25 50 Adaptations Around This Relic o C4 PLANTS Change in place Includes many grasses o Anatomical adaptations Mesophyll cells fix carbon to 4 C compound Bundle sheath cells release CO2 and proceed w Calvin cycle Need to invest energy to make system work Bundle sheath only have PSI so only carry out cyclic e flow o CAM PLANTS Change in time Includes succulents cacti pineapple etc Timing adaptations Stomata open night ONLY Fix CO2 into organic acids During day CO2 release and used
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