Photosynthesis

  1. Thylakoid
    Membrane that contains chlorophyll
  2. What's inside a chloroplast?
    • Double membrane (outer/inner)
    • Inermembrane space
    • Stroma
    • Thylakoid
    • Thylakoid space
  3. Photosynthesis formula
    • 6 Water + 6 carbon dioxide + sunlight ->
    • Glucose + 6 oxygen
  4. History of photosynthesis formula
    • O2 originally thought to come from the CO2
    • van Niel first proposed that O2 came from H2O in 1930s
    • Confirmed in 1950s
  5. How is photosynthesis a redox reaction
    • Water becomes oxidized to become oxygen 
    • Carbon dioxide is reduced to become sugar
  6. Is photosynthesis endergonic or exergonic?
    Electrons increase in potential energy so the reaction is endergonic
  7. What form of energy is light?
    A form of electromagnetic radiation
  8. Photons
    discrete particles with a fixed amount of energy (no mass!)
  9. Why is the sky blue? Why does something appear white? black?
    • This deals with how much wavelengths are making it to your eyes
    • Black absorbs all visible light
    • White reflects all visible light
  10. Pigment
    • Substance that absorbs visible light
    • Different pigments absorb different wavelengths of light
  11. Why do chlorophyll a & b appear green?
    They do not absorb wavelengths in that part of the spectrum
  12. Why do leaves change colors?
    Leaves stop producing chlorophyll so the other chemicals start showing through
  13. Why do carotenoids exist?
    To protect the plant. The pigments pick up the extra energy from the sun
  14. Why does chlorophyll appear green
    It reflects green wavelengths
  15. Two parts of photosynthesis
    • Light reactions
    • Calvin cycle
  16. Light reaction
    • Converts light energy into chemical energy
    • Located in the thylakoid membrane.
    • Light + H2O -> NADPH + ATP + O
    • H2O is split to provide e- and H+
    • NADP+ is reduced to NADPH
    • ATP is produced
    • O2 is given off
  17. Antenna complexes
    Contain pigment molecules which absorb light and transfer the energy to reaction-center complex (i.e light harvesting complex)
  18. Reaction-center complex
    Contains a special pair of chlorophyll a molecules which can reduce the primary electron acceptor
  19. What helps direct energy to the center in the antenna complex?
    • Resonance energy transfer
    • Energy in electron is transferred to nearby pigment
  20. In the thylakoid membranes, what is the main role of the pigment molecules in a light-harvesting complex
    Transfer light energy
  21. As electron pass through the system of electron carriers after leaving photosystem II, they lose energy. What happens to the energy?
    It is used to establish and maintain a protein gradient for the generation of ATP
  22. Photophosphorylation
    The process of making ATP from ATP synthase. This is because the energy is coming from photons
  23. When oxygen is released as a result of photosynthesis, it is a direct by product of?
    Splitting water molecules
  24. Cyclic electron flow
    • Electrons from photosystem I transferred back to ETC
    • Produces ATP instead of NAPDH
  25. How are the light reactions and the Calvin Cycle connected?
    The light reactions provide ATP and NADPH to the Calvin Cycle, and the Calvin cycle returns ADP, Pi and NADP+ to the light reactions
  26. Calvin Cycle
    Uses the chemical energy stored in ATP and NADPH to reduce CO2 to sugar (G3P)
  27. 3 Phases of Calvin Cycle
    • Carbon fixation
    • Reduction
    • Regeneration of CO2 acceptor
  28. Carbon Fixation
    • First phase in Calvin Cycle
    • Rubisco (RuBP carboxylase) attatches to CO2 molecule to RuBP
    • Taking CO2 and fixing it to become an organic molecule
  29. Reduction
    • Second phase in Calvin Cycle
    • Carbon intermediate phosphorylated by ATP
    • Reduction by NADPH and loses the phosphate = G3P
  30. Regeneration of CO2 acceptor
    • Series of steps which utilize ATP to rearrange 5 molecules of G3P to regenerate 3 molecules of RuBP
    • Majority of sugar produced is turned into RuBP
  31. What process is most directly driven by light energy
    Removal of electrons from chlorophyll molecules
  32. What does it mean when CO2 becomes fixed during photosynthesis?
    CO2 becomes bonded to an organic compound
  33. How many times must the Calvin Cycle occur to produce 1 net G3P
    • 3 times
    • For 1 G3p, cycle uses 9 ATP and 6 NADPH
  34. Which doesn't happen in Calvin Cycle?
    Carbon fixation
    Oxidation of NADPH
    Regeneration of CO2 acceptor
    Consumption of ATP
    Release of oxygen
    Release of oxygen
  35. Photorespiration
    • When Rubisco fixes oxygen in place of carbon dioxide.
    • This causes plants to release carbon dioxide
    • It also consumes ATP and decreases photosynthesis by siphoning off material from the Calvin Cycle
  36. When is trouble with Rubisco most prevalent and why?
    • Hot, dry climates
    • Plants close stomata to minimize water loss but this reduces the amount of carbon dioxide available
    • Concentration of oxygen released from light reactions increases favoring oxygen fixation
  37. C3 plants
    Plants that use rubisco for initial carbon fixation
  38. Plants that have alternative modes of carbon fixation to minimize photorespiration
    • C4 Plants
    • CAM (crassulacean acid metabolism)
  39. What happens in C4 plants?
    • Carbon fixation is in a different location from the Calvin Cycle
    • CO2 is initially fixed by PEP carboxylase in mesophyll cells to form a 4-carbon product
    • Product is transported into bundle sheath cells where the CO2 is released and can be added to the Calvin Cycle by rubisco
    • This process uses some energy but it helps ensure that the rubisco fixes only CO2
  40. CAM Plants
    • Carbon fixation is separated from the Calvin Cycle at a different time
    • Plants close their stomata during the day to conserve water and open at night
    • Plants take in CO2 and fix it into organic acids which are stored in vacuoles
    • During the day, when light can supply ATP and NADPH, CO2 is released from the organic acids and enters the cycle
    • This also uses some energy
  41. The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises why?
    Both minimize photorespiration but expend more ATP during carbon fixation
  42. What happens to the sugar produced?
    • 50% is used for cellular respiration
    • Linked together to form cellulose -> build up the cell wall
    • Excess stored as starch in the winter for trees
  43. If you plant a maple seed in your backyard and over the course of many years it grows into a tall tree, where did the increase in mass come from?
    • Air
    • Carbon is pulled out of the air which gets bonded to organic molecules and turned into cellulose
Author
Zaqxz
ID
334927
Card Set
Photosynthesis
Description
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Updated