Photosynthesis 9/19/13

1. Photosynthesis 9/19/13 • autotrophs vs. heterotrophs • light energy • photosynthesis - general process • light-driven reactions • Calvin Cycle

2. PHOTOSYNTHESIS: • production of organic molecules from inorganic molecules • Autotrophs • “self feeders” • make own food • Heterotrophs • “

3. Energy Flow: • energy comes from • plants (producers) use • waste product - • consumers eat • use • waste product - • NOTE:

4. Energy Flow: • converting sun energy to food = • conversion of food to usable energy • usable energy = • NOTE:

5. Light Energy - Visual Spectrum: • sunlight - • shorter wavelengths have • different wavelengths • most solar energy fig. 8.4 • high-energy wavelengths • low-energy wavelengths filtered • pigments in plants

6. What absorbs the light energy? see fig 8.2

7. Absorption vs. Reflectance: • sunlight -- • different pigments • absorbed wavelengths = • energy used • reflected wavelengths - Fig 8.5 • Why do leaves turn red/yellow in the fall?

8. Pigment absorption and color: • in spring/summer – chlorophyll molecules • in fall – chlorophyll

9. Sunlight is considered the ultimate source of energy on the earth because ______. • autotrophs obtain their energy by eating heterotrophs, which obtain their energy directly from the sun, allowing them to break down glucose molecules • heterotrophs obtain their energy by eating producers or other heterotrophs that eat producers, and producers obtain their energy from the sun • organisms forage during the daytime when sunlight is available; during prolonged periods of darkness, plants switch over to fermentation processes instead of photosynthesis • sunlight charges electrons in the atmosphere, which the plants can then absorb through the pores in the leaves and then dump the electrons into the light-independent stage of photosynthesis • the heat from the sun is needed to active enzymes to breakdown organic compounds

10. Stages of Photosynthesis: • Light-driven reactions (photosystems) 2. Calvin Cycle Fig 8.3

11. Electron Carriers: carrying potential energy fig 7.1 • NADP+ (photosynthesis) and NAD+ & FAD (cellular respiration) are • reduced • take the electrons • converted back to

12. see fig 8.6 Light-driven reactions: sun energy excites electrons • sun • pigments • energy • electron acceptor is a molecule that • electron carrier is a molecule that

13. Two Photosystems: figure 8.6 • energy captured and • Photosystem II - electron transport chain • Photosystem I - electron transport chain

14. Where do the electrons come from in the first place? • special enzyme • waste product: see fig 8.6 for overview

15. Photosystem II: capturing energy in ATP • harvest energy Fig 8.8

16. Capturing energy into ATP • concentration of H+ in thylakoid space • ATP synthase • the potential energy • kinetic energy is harvested - Fig 8.8

17. Photosystem I: capturing energy into NADPH • electron re-energized in • electron passed along series of proteins

18. Cyclic electron pathway: • sometimes NADPH accumulates in the cell • plant will carry out cyclic photophosphorylation • at end of PSI, • builds up a concentration Fig 8.7

19. ATP formation during the electron transport chain occurs in a series of steps. Place the following sequence of events in order. a concentration gradient of hydrogen ions builds up across the membrane. ADP & P are joined to form ATP by harvesting energy released protein channel opens and hydrogen rushes down its concentration gradient electrons are passed from one carrier to the next shuttling hydrogen ions across membrane a. I – III – IV – II b. IV – III – I – II c. II – III – I – IV d. II – IV – I – III e. IV – I – III – II

20. Photosynthetic electron transport system -- (review) • photosystem II - • photosystem I - Products from light-driven reactions: fig 7.8