BIOL 111 301 1st Edition Lecture 12Outline of Last Lecture I. Review/PreviewII. Nature Of Light III. PigmentsIV. What happens to the absorbed light?V. Light Reactions: converting solar energy to chemical energyVI. How much energy did we harvest from the sun?Outline of Current LectureI. ReviewII. OVERVIEW OF CALVIN CYCLEIII. Melvin CALVIN CycleIV. Photorespiration: an evolutionary relic that causes problemsV. Adaptations Around This RelicCurrent Lecture- Reviewo 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 CYCLEo 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 G3Po Need 3 turns of the cycle for one G3P- Melvin CALVIN Cycleo PHASE 1: CARBON FIXATION (3x) CO2 + 5-C RuBP 6-C 2 3-C Rubisco—most abundant enzyme on eartho PHASE 2: REDUCTION Input ATP (6 ATP/3 cycles) Input 2e- (6NADPH 6NADP+/3 cycles) Output 1 3-C G3Po 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 problemso Ancient atmosphere Before photosynthesis: increased CO2, decreased O2 Cyanobacteria- 1st to photosynthesize- 2.7 billion years agoo Ancient atmosphereo Rubisco can bind CO2 OR O2—When?o Rubisco- Ribulose bisphosphate carboxylase oxygenaseo Why is this a problem? Releases CO2 Uses ATP in the process Decreases photosynthesis output by 25-50%- Adaptations Around This Relico C4 PLANTS—Change in place, Includes many grasseso 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- flowo 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
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