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Photosynthesis

Photosynthesis. Let the sun shine….. Hooray for photosynthesis!!!!. The equations…. Cellular respiration-highly exergonic C6H12O6 + O2  CO2 + H2O + ATP!! Energy released thru oxidation of glucose Photosynthesis-highly endergonic Light + CO2  C6H12O6 + O2

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Photosynthesis

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  1. Photosynthesis Let the sun shine….. Hooray for photosynthesis!!!!

  2. The equations… • Cellular respiration-highly exergonic • C6H12O6 + O2  CO2 + H2O + ATP!! • Energy released thru oxidation of glucose • Photosynthesis-highly endergonic • Light + CO2  C6H12O6 + O2 • Light energy used to reduce CO2

  3. Stroma • ATP produced in stroma • Calvin cycle • Thylakoid membrane • Photosystems embedded • ETCs • ATP synthase • Thylakoid space • H+ conc. gradient

  4. Overview Produce energy Required for dark reactions “fix” CO2 into glucose Highly endergonic

  5. Light dependent reactions • Occur in thylakoid space & membrane • Light strikes chlorophyll • E- are boosted to higher energy level & travel down an ETC • Released energy captured to form ATP & NAPH • Water molecules borken apart to replace lost e- • Light independent reactions-carbon fixing • Uses energy captured in ATP & NADPH to reduce CO2 to sugar • Occurs in stroma

  6. Absorption pigments • Light energy must be absorbed to be of any benefit • Pigments absorb certain wavelengths of light, which causes altered structure • Chloroplasts contain several pigments • Chlrophyll-absorbs violet, blue, red • Carotenoids-absorb blue & green • Phycocyanins-absorb green

  7. What happens when chlorophyll absorbs light? • An e- becomes energized & moves to higher orbital • This is unstable-e- will normally release energy & move back to its original orbital • In photosynthesis, e- is captured by ETC

  8. What is a photosystem? • Located in thylakoid membrane • Composed of a reaction center(chlorophyll), ,accessory(antennae) pigments, & an ETC • PSI- • evolved 1st, • cotains a dimer of chlorophyll, • can operate independently of PSII, • its ETC makes NADPH • PSII • Supllies e- to PSI • ETC produces ATP (photophosphorylation) • Accessory pigments absorb light & pass it chlorophyll • Only chlorophyll loses e- to ETCs

  9. Light causes e- to become energized in PSII Jump to higher level

  10. Water is split to replace e-

  11. E- captured by cytochromes in ETC Energy used to push H+ from stroma to space Gradient used to produce ATP in stroma

  12. E- end up in PSI, which has also lost e- To its ETC

  13. PSI ETC gives its e- to NAD-an e- shuttle, it carries e- to calvin cycle

  14. Cyclic e- flow-used when no NADP is available-(calvin cycle uses ATP faster than NADPH) This ETC shuts down No NADPH or O2

  15. RuBP carboxylase CO2 is reduced RuBP is regenerated Reverse reactions of glycolysis G3P

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