Bio CH 10

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Bio CH 10
2011-04-06 21:28:13

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  1. Autotrophs
    • Photosynthesis is performed by autotrophs
    • --make their own food by CO2, H20, light
    • Specifically photoautotrophs (vs/ chemoautotrophs)
    • Autotrophs are the primary producers
    • --store solar energy in sugars
    • --first source of organic compounds
  2. Leaf Structure
    • "Middle" leaf tissue captures light
    • Gases enter/exit leaf via stomata (pores
    • Water absorbed by roots, transported to leaves
    • CO2+H2O+light are the requirements for photosynthesis
  3. Chloroplasts structure
    • Site of photosynthesis in plants (organelles)
    • All green parts of the plant have chloroplasts
    • green pigments
    • absorbs light energy

    • Two outer membranes
    • -small intermembrane space
  4. Photosynthesis equation
    • 6CO2+6H20+light->C6H12O6+6O2
    • equation is revers of respiration, but not the reverse of respiration
    • Water is split and O2 is released
    • Carbon in CO2 fixed in sugar (glucose)
  5. Stroma
    • Internal fluid of chloroplast
    • DNA, ribosomes, enzymes
  6. Thylakoids
    • Internal membrane system of chloroplast
    • flattened sacs
    • Thylakoids can be in stacks
    • --Granum (grana plasma)
  7. Sunlight energy and visible spectrum
    • Light is electromagnetic energy
    • variable by wavelength
    • Visible light is absorbed by chloroplasts (includes colors that we see (ROYGBIV)
    • Pigments are light receptors
    • Ex. Chlorophyll absorbs red/blue and reflects green
  8. Photorespiration
    • Wasteful process--different than cellular respiration
    • Rubisco picks up the O2 and not CO2
    • -Only CO2 reacion will fix carbon but O2 preferentially taken in certain conditions/ (no net carbon uptake, sugar can't be made)
    • Occurs with high temperature and water stress
    • Alternative mechanisms decrease photorespiration (C4, CAM photosynthesis)
  9. CAM Photosynthesis
    • Crassulacean acid metabolism (specimen in hot dry climate-like cacti)
    • Open stomata (pores) at night and closed during the day saves water, less drought, less photorespiration.
    • -Avoid evaporation during the heat of the day
    • -Store CO2 cells until daylight
    • CO2 extracted, then normal Calvin cycle occurs. ATP and NADPH (light rxns) are available
  10. C4 Photosynthesis
    • Plants in hot, dry climate (sugarcane)
    • Calvin cycle preceded by different fixation
    • -initially by rubisco
    • CO2 is fixed, transported, and concentrated
    • -Fixed into a 4c molecule first (mesophyll)
    • -4C molecule moves to bundle sheath cell (unique leave anatomy)
    • -CO2 extracted and normal Calvin cycle occurs
    • Calvin cycle proceeds in high CO2 environment (Rubisco picks up CO2, photorespiration avoided)
  11. Role of light energy
    • light energy excites chlorophyll
    • chlorophyll loses electron
    • NADP+ accepts the electron then reduces to NADPH
  12. Role of water
    • water molecule is split
    • replaces chlorphyll electron, O2 released
    • ATP produced via photophosphorylation
  13. Linear pathways
    • Photosystems help synthesize NADPH and ATP
    • -light is the energy source (light reactions)
    • 1) Light absorbed by PS II, e- released
    • 2) excite electron by 1 degree receptor
    • 3) Water is split to replace PS II electron (oxygen created as biproduct)
    • 4)Electron moves to PS I, via electron transport chain
    • 5) ATP synthesis via e- transport chain
    • 6) PS I releases excited electron
    • 7) Second electron transport chain
    • 8) Ends in NADP+ + H+ +e- -> NADPH
  14. Chlorophyll A/B
    • A: Plant pigments directly involved with light reactions
    • B: very similar in structure to A.
  15. Carotenoids
    • Orange/Yellow pigments
    • Broaden spectrum of light used for photosynthesis
    • protects against excessive light energy
  16. Photosystem I
    absorbs 700 nm light best
  17. Photosystem II
    • absorbs 680 nm light best
    • functions first and then supplies PSI with e-
  18. Reaction Centers
    • Reaction center complex
    • -Has a pair of central Chlorophyll A molecules
    • -Recieves most of surrounded absorbed energy
    • Reaction center Chlorophyll A loses electron
    • -primary electron acceptor recieves excited e-
  19. Chemiosis
    • •Produces ATP in light reactions
    • –As a result of electron transport chains
    • –Very similar to mitochondrial process
    • •Creates high [ H+ ] across membrane
    • –PS: sunlight drives electron transport
    • •Gradient across thylakoid membrane
    • –Resp: food oxidation drives electron transport
    • •Gradient across inner mitochondrial membrane
    • •Allows ATP synthase to produce ATP
  20. Products of Light RxN
    ATP produced via photophosphorylation
  21. Calvin Cycle
    • Dont require light energy
    • generally occur in daytime
    • Carbon Fixation- incorporates CO2 from air and "Fixes" carbon into sugar molecules
    • Requires NADPH and ATP from light rxns and supply energy and electrons to reduce fixed carbon.
  22. calvin cycle step 1
    • 1). Carbon Fixation
    • –CO2 attaches to 5C sugar RuBP
    • •RuBP = ribulose bisphosphate
    • •Reaction facilitated by RuBP carboxylase
    • –“Rubisco”: most abundant enzyme on earth
    • –Creates unstable 6C intermediate
    • –6C splits and forms two 3C molecules
    • •3-phosphoglycerate (3PGA)
  23. Calvin Cycle step 2
    • Reduction
    • –3C molecule is phosphorylated & reduced (to
    • G3P)
    • •Phosphorylated by ATP
    • •Receives electrons (reduced) from NADPH
    • –Some glyceraldehyde-3-P (G3P) leaves cycle
    • •Used to make glucose
  24. Calvin Cycle Step 3
    • Regeneration of RuBP
    • G3P remaining in cycle forms RuBP
    • -ATP required to transform G3P