BIOLOGY 151 1st Edition Lecture 27 Outline of Last Lecture 1. Chemiosmosis2. Complexities with respiration #13. Fermentation4. What if there is oxygen?5. Complexities #2: What if there's no sugar?6. Complexities #3: Homeostatic control7. Where do animals and fungi get their energy-yielding organic molecules?8. Chloroplast9. Light Reactions vs. Dark Reactions10. Calvin Cycle11. Calvin Cycle x3 - know this12. Photorespiration - When good rubisco goes bad!Outline of Current Lecture 1. Calvin Cycle (x3) 2. Photorespiration - when good rubisco goes bad3. To keep CO2 concentration high...4. Light Reactions vs. Dark Reactions 5. Pigments absorb light energy6. Photosystem 2 gives high energy electrons to H+ pumping electron transport chains7. Photosystem 18. Why do cyclic scheme?Current Lecture - 3/23/15- if 3 CO2s enter, one G3P can be removed without stopping the Calvin cycle- can't get more carbon out than you put in Calvin Cycle (x3):- 1) Carbon fixation - 3 RuBp + 3CO2 --> 6 3-carbon chains, using rubisco- 2) Reduction - produces 6 G3Ps, one of which is used to make sugars- 3) Regeneration - Remaining 5 G3Ps regenerate 3 5-carbon RuBPs- 3x through Calvin Cycle uses 9 ATPs, electrons in 6 NADPHPhotorespiration - when good rubisco goes bad:- when O2 concentration gets much higher than CO2, rubisco adds O2 to 5-carbon RuBP, some of product makes CO2- terrestrial plants in a dry environment have a problem with thisTo keep CO2 concentration high...:- C4 and CAM plants fix and "store" CO2 release before Calvin Cycle- 1) CO2 incorporated into 4-carbon organic acids (carbon fixation)- 2) Organic acids release CO2 to Calvin cycleLight Reactions vs. Dark Reactions: - use light energy to make ATP, electrons in NADPH and O2 (light)- use ATP, electrons in NADPH and CO2 to make sugar (dark)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- light in thylakoid membrane- dark in stroma- pigments in photosystems use light to excite and donate electrons to electron acceptor- photosystem 2: donated electrons replaced by taking 2 from H2O to make oxygen- only one that can grab electrons from water, not electron transport chainPigments Absorb Light Energy:- main pigments is chlorophyll a- magnesium-containing ring- light excites electron in ring to higher, unstable energy- accessory pigments = carotenoids to absorb different wavelengths to light, protect chlorophylls from bleaching- red and blue wavelengths best for driving photosynthesis- pigments in photosystems use light to excite and donate electrons to electron acceptorPhotosystem 2 gives high energy electrons to H+ pumping electron transport chain:- pumps H+ into thylakoid- increase concentration of proteins in linear thylakoid spacePhotosystem 1:- gets and excites electrons from H+ pumping electron transport chain- excited electron go 1 of 2 directions:- 1) donated to NADP+ to make NADPH- Non-cyclic scheme - the z scheme- makes both ATP via H+ pumps and NADPH after PS1- non-cyclic (linear) electron flow (z scheme)- pumps H+ inside thylakoid, H+ gradient drives ATP synthase- 2) Go back to pumping electron transport chain to make ATP- Cyclic electron flow - uses Photosystem 1 to pump H+ (no NADPH made)Why do cyclic scheme?:- Calvin cycle needs 9 ATPs and 6 NADPH, so use cyclic scheme to make more ATP?- use in cells that do not use Calvin Cycle?- more photodamage when electrons not moving?- do plant cells need mitochondria?- yes, because night time, have parts not going through photosynthesis- need mitochondria- Calvin Cycle makes more stable molecules for storing
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