1 / 19

Biology 102

Biology 102. Photosynthesis 1. Lecture Outline. Back to the dinosaurs… What is photosynthesis (and “who” does it)? The light-dependent reactions. 1. Back to the dinosaurs…. 2. What is photosynthesis?. Photo: “light” Light energy is stored in the energy of chemical bonds.

mahsa
Download Presentation

Biology 102

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. Biology 102 Photosynthesis 1

  2. Lecture Outline • Back to the dinosaurs… • What is photosynthesis (and “who” does it)? • The light-dependent reactions

  3. 1. Back to the dinosaurs…

  4. 2. What is photosynthesis? • Photo: “light” • Light energy is stored in the energy of chemical bonds. • Synthesis: “build” • Organic molecules are built from inorganic molecules • Carbon-carbon bonds are formed! • The formulas for photosynthesis and cellular respiration • Write it down!

  5. The relationship between photosynthesis and cellular respiration

  6. Organisms that photosynthesize • Eukaryotes that photosynthesize • Plants (all!) • Some protists • Marine phytoplankton • Freshwater and marine algae • Prokaryotes that photosynthesize • Example: Cyanobacteria

  7. Leaves (plants only) and chloroplasts (eukaryotes only) • Chloroplasts within mesophyll cells • Epidermis is thin and transparent (why?)

  8. Photosynthesis involves two sets of reactions • The light-dependent reactions (“photo”) • Light energy is captured from the sun and turned into chemical energy • The energy is temporarily stored within energy carrier molecules • The light-independent reactions (“synthesis”) • Temporarily-stored energy is used to build the glucose molecule from carbon dioxide and water • Energy is stored in the carbon-carbon bonds!

  9. 3. The light-dependent reactions • What is accomplished? • Light energy is turned into chemical energy • Overview of what happens • Light is captured by pigments in the chloroplast • Electrons of the pigments “absorb” the energy • Electrons are transferred between compounds • ATP and NADPH are both formed

  10. What is light? • Light is one type of energy within the electromagnetic spectrum • Different wavelengths of light have different amounts of energy

  11. What wavelengths of light do different plant pigments absorb? • Note that the color you see is the color that is not absorbed, but rather reflected!

  12. How is the energy of light actually captured?

  13. Summary of light-dependent reactions • Light energy is “absorbed” by pigments of the light-harvesting complex and passed to a special chlorophyll molecule, the “reaction center” • An electron in the reaction center chlorophyll is excited and “jumps” from the chlorophyll molecule to… • An electron acceptor at a higher energy level

  14. The electron is passed between molecules of the electron transport system • The energy gained (from moving the electron to lower energy compounds) is used to synthesize ATP

  15. The electron ends up in another chlorophyll molecule (Photosystem I) • An electron in the reaction center chlorophyll is excited and “jumps” from the chlorophyll molecule to… • An electron acceptor at a higher energy level

  16. The electrons are transferred along a second electron transport chain (along with an H+ ion…) to a molecule of NADPH

  17. Where did the mysterious H+ come from? What about the missing electron? • It’s all about the water!

  18. Review of light-dependent reactions

  19. End result of light-dependent reactions • Energy from sun was captured and converted to chemical energy • ATP and NADPH • Water was split to provide e- and H+ and generated oxygen as a bi-product!

More Related