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Bell-Ringer

Bell-Ringer. What enzyme is involved in chemiosmosis, through which H+ ions flow in order to make ATP? What is ATP made out of ? (What two molecules?) On your sheet of paper, draw a big chloroplast with one granum. Label the granum, the thylakoids, the stroma , and the thylakoid space. A.

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Bell-Ringer

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  1. Bell-Ringer What enzyme is involved in chemiosmosis, through which H+ ions flow in order to make ATP? What is ATP made out of? (What two molecules?) On your sheet of paper, draw a big chloroplast with one granum. Label the granum, the thylakoids, the stroma, and the thylakoid space.

  2. A B ?H K I + J M L G E D C

  3. Chapter 10 (Part 2) Light Reactions of Photosynthesis AP Biology

  4. During the light reactions, electrons flow throughout the photosystems. As these e-’s flow, energy is transformed from sunlight into ATP and NADPH. • There are two types of electron flow: • Non-cyclic electron flow/ photophosphorylation 2. Cyclic electron flow/ photophosphorylation

  5. Noncyclic Electron Flow Steps • Photon of light strikes PSII  an e- from chlorophyll a in PSII is ‘excited’ to higher energy state  e- is captured by primary e- acceptor • Chlorophyll a now has an electron void 2. An enzyme splits water e-s from water replace those which chlorophyll a lost to primary e- acceptor H20  2 H+ + 2e- + ½ O2 (2 O’s combine and O2 is released)

  6. H H O e e H+ H +H H e- e- Inhale, baby! Deeper Look 1 2 O O e e Photosystem IIP680 chlorophyll a

  7. 3. Primary e- acceptor gives its e-’s to an Electron Transport Chain • proteins in thylakoid membrane pass e-s (become reduced) • “Fall” of e-’s down the chain is exergonic  releases energy to make ATP

  8. 4. Chemiosomosis– the process that forms ATP during light reactions • Protons (H+) are pumped ACTIVELY(against concentration gradient) into thylakoid space fromstroma as electrons travel through electron transport chain #1 • Higher [H+] in thylakoid space than in stroma proton motive force/ electrochemical gradient • Protons (H+) come from the split of water that happened previously • H+’s then DIFFUSE back through the thylakoid membrane • H+’s flow down concentration gradient from thylakoid space back into stroma • H+’s flow through ATP synthasechannels in the thylakoid membrane • Produces ATP in the stroma of the chloroplast • ATP will be used in the Calvin cycle

  9. Thylakoid Space Active Transport Stroma

  10. 5. While all this is happening in PSII, PSI absorbs light energy an e- from chlorophyll a in PSI is ‘excited’ to higher energy state  e- is captured by primary e- acceptore-goes down electron transport chain #2 6. Electrons from the end of the ETC in PSII will fill the electron void in PSI’s chlorophyll a • So… PSI & PSII are connected to one another by the transfer of high-energy electrons through an ETC

  11. 7. NADP+ in the stroma becomes reduced using NADP reductase • NADP+ + 2H+ + 2e-  NADPH from split from PSI’s ETC water

  12. Non cyclic light reactions & Chemiosmosis

  13. A B ?H K I + J M L G E D C

  14. Antennae pigments

  15. Non Cyclic Electron Flow (Overview) Light  P680  ATPmade  P700  NADPH made O2 released

  16. Noncyclic Electron Flow Animations • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html# • http://www.fw.vt.edu/dendro/forestbiology/photosynthesis.swf • http://www.web.virginia.edu/gg_demo/movies/figure18_12b.html • http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html • http://www.sumanasinc.com/webcontent/animations/content/harvestinglight.html • http://www.tvdsb.on.ca/westmin/science/Biology12/Metabolic%20Processes/lightrxn.htm • http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf

  17. Tutorials (Light Reactions) • http://faculty.nl.edu/jste/noncyclic_photophosphorylation.htm • http://www.bio.miami.edu/~cmallery/255/255phts/255phts.htm • http://www.biology.arizona.edu/biochemistry/problem_sets/photosynthesis_1/photosynthesis_1.html

  18. Homework • On your drawing of a chloroplast, illustrate the non-cyclic portion of the light reactions of photosynthesis. • Label each step of the process (get these steps from your notes/this PowerPoint). • Summarize each step of the process. • Draw arrows when appropriate • ie. arrows showing movement of electrons, flow of H+’s, movement of O2, etc. • Label all of the “players” involved • Ie. Photosystem II (PSII), Photosystem I (PSI), chlorophyll a, Thylakoid Membrane, ADP + Pi, etc.

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