Meeting 5

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Author:
mse263
ID:
137215
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Meeting 5
Updated:
2012-02-23 15:05:22
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Photosynthesis
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Description:
Exam1 MCBII
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  1. heterotroph
    organism that cannot fix carbon and uses organic carbon for growth
  2. autotroph
    an organism that produces complex organic compounds (carbohydrates, fats, and proteins) from simple inorganic molecules using energy from light (by photosynthesis)
  3. photosynthesis can be divided up into 4 processes that occur in different parts of the chloroplast:
    1) absorbtion of light + formation of a high energy electron (?) & formation of O2 to H2O

    2) reduction of NADP+ to NADPH b/c of electron transport, and the generation of proton motive force

    3) ATP is made

    4) carbon fixation: conversion of CO2 into carbs
  4. 1) absorption of light
    • -this is done by chlorophylls attached to thylakoid (3rd) membrane; specifically the multiprotein complex PSII
    • -the energy from light is used to remove electrons from water (e- donor for green plants)
    • -and are transfered to quinone Q (primary e- acceptor)
  5. PSII (photosystem II)
    where the oxidation of water to molecular oxygen takes place

    chlorophyll of choice: P680
  6. chlorophyll
    consist of porphyrin ring attached to hydrocarbon side chain (phytol tail); has a central Mg+ ion + additional 5-carbon ring!

    • -want the phytol tails (CH) so the chlorophyll can attach to hydrophobic regions of membrane proteins/attach to membrane
    • -want the Mg (metal) b/c they have physical states in which e- can be propelled outward then drop back = energy released
  7. 2) E- transport & Proton-Motive Force
    • -e- accepted by the quinone (primary e- acceptor) move through a series of carriers until they are 'terminally' accepted by NADP+...this reduces it to NADPH
    • -that takes place in PSI

    • -coupling: e- transport across thylakoid membrane is COUPLED with proton movement FROM the stroma TO inside the thylakoid lumen
    • -this means the pHlumen < pHstroma
  8. PSI (photosystem I)
    reduces the electron carrier NADP+

    chlorophyll of choice: P700
  9. 3) ATP Synthesis
    • -the movement of protons DOWN their concentration gradient
    • -from the thylak lumen TO the stroma (high H+ to low)
    • -this happens through the F0F1 complex
    • -is coupled with the synthesis of ATP from ADP * Pi
  10. 4) Carbon Fixation (dark reactions)
    • -Calvin cycle
    • -now there's ATP and NADPH in the system
    • -these high energy molecules drive the construction of 6-carb sugar polymers from CO2 and H2O
  11. grana
    stacks of thylakoids

    a stroma thylakoid is a thylakoid membrane that ISN'T stacked
  12. stroma
    fluid inside the chloroplast; located outside the thylakoid
  13. thylakoid
    3rd inner membrane in a chloroplast
  14. What percentage of the air is CO2?
    .03%; enough to sustain all life
  15. OEC contains a “cubane-like Mn3CaO4 cluster”
    responsible for being able to pull e-'s off the high electronegative molecular oxygen? water?
  16. we have cyclic electron flow becuase:
    • that's how we make ATP
    • ex. the plant might have enough carbs, but still needs ATP for a physiological function
  17. why do plants shuttle the LHCII complex between grana and unstacked thylakoids that help regulate NADPH/ATP ratios?
    • to adjust the wavelength of absorbed light, like to be able to absorb more light of different wavelength
    • -especially useful for different times in the day (at the end of the day there's more red light = longer wavelength)

    - shuttling is phosphorylation dependent

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