Lecture 9.pdf

? Announcements: - bring calculator to lab - test on Friday ? Light reactions (finish) ? Calvin cycle - the dark side of photosynthesis ? CAM - when it?s cool to be crass ? C4 photosynthesis - only dangerous to C3 plants Monday, 21 September 2009 http://en.wikipedia.org/wiki/File:Plagiomnium_affine_laminazellen.jpeg The thylakoid energy carrier factory ATP NADPH NADP + reductase: an enzyme that takes e - , H + and NADP + and creates NADPH ATP synthase: an enzyme that puts the 3rd. P onto ADP to make ATP using the power of chemiosmosis Figur e 10.17 ADP+P One thylakoid from a granum photosystem I photosystem II path of H + ions path of e - H + H + O e - e - H2O H + to the Calvin cyclewater split inside thylakoid, oxygen released, electrons replace those lost, and hydrogen ions used to make ATP Visualizing photosystems Figure 7-3, p. 128, in Raven, Evert and Eichhorn. Biology of Plants, 6th. ed. W. H. Freeman and Company. The electron micrograph at right was created using the freeze- fracture technique (see figure 7.04), and shows photosystems (primarily PSII) embedded in stacked thylakoid membranes. Figure 7.04 Visualizing ATP synthase Figure 2: Biochemical Journal 2000. 346: 41-44. This electron micrograph shows an isolated fragment of membrane with ATP synthase enzymes still attached http://en.wikipedia.org/wiki/File:ATPsynthase_labelled.png Very nice animation: http://video.google.com/googleplayer.swf?docid=3707071120350566763 ? Announcements: - bring calculator to lab - test on Friday ? Light reactions (finish) ? Calvin cycle - the dark side of photosynthesis ? CAM - when it?s cool to be crass ? C4 photosynthesis - only dangerous to C3 plants Monday, 21 September 2009 Melvin Calvin Image made available by textbook publisher The two sides of photosynthesis light reactions ?dark? reactions Figure 10.5 Moving over to the dark side... Figure 10.18 Carbon atoms (gray circles) form the backbone of all organic molecules Rubisco is the name of the enzyme that attaches the 1 carbon from CO2 to an existing 5-carbon organic molecule (RuBP) to create 2 3-carbon molecules of PGA. PGA Rubisco is the most abundant protein on earth. It alone makes up about 1/4 of the dry weight of a leaf! Most plants are called C3 plants because they only fix carbon using RuBisCO, which results in 3-carbon PGA molecules Moving over to the dark side... Figure 10.18 ATP and NADPH created in the light reactions are needed to rearrange PGA into G3P One G3P leaves to be incorporated into more complex sugars (such as sucrose) Note that 3 carbons have entered as CO2 molecules and 3 carbons have left in the form of one G3P Moving over to the dark side... Figure 10.18 More ATP from the light reactions is needed to rearrange 5 G3P molecules (15 carbons total) into 3 RuBP molecules (also 15 carbons total) ? Announcements: - bring calculator to lab - test on Friday ? Light reactions (finish) ? Calvin cycle - the dark side of photosynthesis ? CAM - when it?s cool to be crass ? C4 photosynthesis - only dangerous to C3 plants Monday, 21 September 2009 http://www .flickr .com/photos/succulentisima/1443162989/ Genus: Crassula Family: Crassulaceae Crassulacean Acid Metabolism (CAM) Day !Stomates closed !No water lost !No gas exchange !CO2 released from malate in vacuoles !Photosynthesis happens Night !Stomates open !Little water lost !Gases exchanged !CO2 captured in form of malate and stored in vacuoles !No photosynthesis Normally... stomata are open when photosynthesis is occurring, which is during the daytime. CAM plants are adapted to deserts CAM plants are adapted for dry environments http://farm1.static.flickr.com/23/183526432_7f3477b1ef.jpg There?s always a trade off... cytoplasm vacuole PEP CO2 malate Night malate Day Note that CAM requires energy (ATP) and has to fix carbon twice ATP PEPADP+P Carbon fixation 1 Carbon fixation 2 Sour Punch candy image and ingredients list: http://www.sugarstand.com/sc/sc0025-sour-punch-straws.htm malate dissolved in water forms malic acid, which is sour tasting Ingredients: CORN SYRUP, WHEAT FLOUR, SUGAR, CITRIC ACID, MALIC ACID, TARTARIC ACID, GLYCERYL, MONOSTEARATE, GLYCERINE, ARTIFICIAL FLAVORS, COLOR ADDED malic acid decreases during day, making leaves less sour- tasting CO2 pyruvate ? Announcements: - bring calculator to lab - test on Friday ? Light reactions (finish) ? Calvin cycle - the dark side of photosynthesis ? CAM - when it?s cool to be crass ? C4 photosynthesis - only dangerous to C3 plants Monday, 21 September 2009 Nature 416: 578 (2002) Kranz (wreath) anatomy Wreath image: http://www.willametteevergreen.com/fundraiser_products.htm Not to be outdone, C4 plants find a different way to use malate Figure 10.20b Figure 10.20a Figur e 10.19 separated in space (C4) Two carbon fixations are: separated in time (CAM) Paul Lewis 21Sep2009.key