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Photosynthesis

Photosynthesis. Light Absorption. Sun gives off visible light (ROYGBIV) Unabsorbed light reflects to our eyes Most green light not absorbed by leaves Chlorophyll absorbs sunlight Absorb mostly reds and blues. The Chloroplast. Site of photosynthesis

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Photosynthesis

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  1. Photosynthesis

  2. Light Absorption • Sun gives off visible light (ROYGBIV) • Unabsorbed light reflects to our eyes • Most green light not absorbed by leaves • Chlorophyll absorbs sunlight • Absorb mostly reds and blues

  3. The Chloroplast • Site of photosynthesis • Thylakoid membranes: light dependent reactions • Stroma (fluid interior): light independent reactions

  4. Stomata: pore underneath leaves through which gases enter/exit

  5. Photosynthesis Overview • Two Stages • 1) Light Dependent Reactions • Photosystems: groups of molecules that capture/transfer energy • Creates: O2, ATP, NADPH • 2) Light Independent Reactions • Creates: Glucose

  6. Light Dependent Reactions: Photosystem II Step 1: Chlorophyll absorbs sunlight • Chlorophyll e- become excited & transfer to thylakoid membrane • Thylakoid membrane becomes negatively charged • Starts an electron transport chain

  7. Step 2 & 3: H2O broken into H+, e-, and O • e- replace those lost by chlorophyll • O waste • H+ pumped inside the thylakoids and accumulate

  8. Thylakoid membrane Thylakoid membrane becomes negatively charged e e e e e e e e e chlorophyll chlorophyll e e H e Electrons replace those which left chlorophyll H e e H O e H H H Oxygen waste is released O O

  9. Light Dependent Reactions: Photosystem I • Chlorophyll absorbs sunlight • Chlorophyll e- become excited & transfer to thylakoid membrane • Accumulate with those from photosystem II e- e- e-

  10. NADPH produced (H taxi) • e- causes H+ to bond with NADP • ATP produced • H+ ions diffuse and bond ADP with Pi H+ H+ H+ ATP ATP

  11. Light Dependent Summary • O2, ATP, NADPH created • NO GLUCOSE CREATED!

  12. Light Independent Reactions (Calvin Cycle) • Step 1: CO2 bonds with RuBP (5C) molecule to make a 6C molecule

  13. 6C molecule RuBP CO2

  14. Step 2: 6C molecule splits into two PGAL molecules (3C) • ATP & NADPH provide the energy

  15. NADPH 6C molecule ADP ADP ATP ATP

  16. Some PGAL (3C) bonds to make glucose (6C) Some PGAL recycled to start the cycle over

  17. glucose! glucose!

  18. Light Independent Summary • CO2, ATP, & NADPH create glucose

  19. Your essay question on the next test! Trace the flow of energy, including ATP, from the sun to your muscles, after eating a green leaf salad.

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