1 / 20

Understanding Chemiosmosis and Light Reactions in Photosynthesis

In this tutorial, we delve into the biochemical processes involved in chemiosmosis and the light reactions of photosynthesis. We will explore the role of specific enzymes in ATP synthesis as H+ ions flow through ATP synthase. Learn about the construction of ATP from ADP and inorganic phosphate, and visualize chloroplast structures including thylakoids and stroma. This session highlights the exciting flow of electrons in Photosystems I and II and their contribution to the creation of NADPH and the release of oxygen.

galvin-griffin
Télécharger la présentation

Understanding Chemiosmosis and Light Reactions in Photosynthesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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.

More Related