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Photosynthesis

Photosynthesis. Chapter 8 (pages 200-219). Where energy comes from. Plants and some other types of organisms use light energy from the to produce food Autotrophs : organisms that make their own food Use the sun’s energy to help make their food

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Photosynthesis

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  1. Photosynthesis Chapter 8 (pages 200-219)

  2. Where energy comes from • Plants and some other types of organisms use light energy from the to produce food • Autotrophs: organisms that make their own food • Use the sun’s energy to help make their food • Heterotrophs: organisms that do not make their own food • Where does their energy come from?

  3. ATP • Adenosine Triphosphate • One of the principal chemical compounds that cells use to store and release energy • Composed of: • 5-carbon sugar (ribose) • Adenine • Three phosphate groups 3 phosphate groups adenine ribose

  4. ADP • Adenosine Diphosphate • Looks almost like ATP, but only two phosphate groups • When a cell has energy available to store, tacks on that extra phosphate group to ADP  ATP

  5. Storing vs. Releasing Energy • To store energy  add on a phosphate group • To release energy  remove a phosphate group

  6. Using ATP • Active transport • Cell movement • Responding the chemical signals • Protein synthesis • Nucleic Acid synthesis • ATP is not a good for storing energy  glucose contains 90x the chemical energy that one ATP molecule has. • Regenerate ATP from ADP by using energy in foods like glucose

  7. The Scientists of Photosynthesis • Van Helmont: found plants gain mass from water • Priestley: plants release oxygen • Ingenhousz: plants produce oxygen in sunlight, not in dark • Mayer: proposed plants convert light into chemical energy • Calvin: traced chemical path that carbon follows to form glucose (Calvin Cycle)

  8. Photosynthesis • Photosynthesisthe use of energy from sunlight to convert water and carbon dioxide into high-energy carbohydrates – sugar and starches – and oxygen as a waste product

  9. Light and Pigments • In addition to H2O and CO2, light and chlorophyllneeded • Where’s chlorophyll found? • Plants gather sun’s energy with light-absorbing molecules called pigments • Principal pigment in plants  chlorophyll • Two types: chlorophyll a and chlorophyll b • Absorb light in blueand redregion of VS spectrum • When light is absorbed, energy levels of electrons rise  this is where it all starts!

  10. Inside a Chloroplast Sac-like structure; Contains the photosynthetic pigments, reaction centers for LDR, and the electron transport chain Granum The inner fluid of the chloroplast between the grana which contains various enzymes and where the Calvin Cycle occurs Stack of thylakoids Stroma Thylakoid

  11. Electron Carriers • Sunlight excites electrons – hold energy • Would you want to transport the electron yourself or have something else transport it? • Carrier needed to transport excited electron • Transporter known as = electron transport chain • Actual Carrier = NADP+ • Holds 2 high energy electrons • Holds H+ NADP+ H+ - e- e-

  12. Light Dependent Reactions

  13. Basically the LDR steps are.. • Light excites electrons – moved from PSII – PSI via the ETC • H2Ogets ripped apart to replace the electrons • We get O2 (yay!) and H+ gets shoved into the inner-membrane space • Electrons get picked up by NADP+  NADPH • H+ sneaks through ATP synthase and cranks it • Cranking connects a phosphate group to ADP  making ATP!  (chemiosmosis!)

  14. Calvin Cycle • Also known as the light independent reactions (or dark reactions) • No light required for them to start • Occur in the stroma of the chloroplast • Use products of LDR as their reactants NADPH, ATP • Give the products NADP+, ADP, high energy sugars • Multiple steps!

  15. Calvin Cycle • Multiple steps take CO2 and convert into multi-carbon containing molecules • Step 1: 6 CO2 and 6, 5-Carbon Molecules  12, 3-Carbon Molecules • Step 2: • ATP  ADP (energy storage for LDR) • NADPH  NADP+ (electron carrier for LDR) • Step 2: 12, 3-Carbon Molecules  2 fall off to make sugar (remember 6 carbons are in a monosaccharide) • Step 3: 10 3-Carbon Molecules  6, 5-Carbon Molecules • ATP  ADP

  16. Calvin Cycle GLUCOSE

  17. Quick review

  18. Factors that alter photosynthesis • Water availability • Which scientist figured this out? • Intensity of light • Which scientists figured this out? • Temperature • What temperature do enzymes function best?

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