The Hydrogen Atom

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The Hydrogen Atom

• An electron has a negative charge
• A proton has a positive charge
• Hydrogen atoms have one electron and one proton
• Absorption-an electron absorbs energy and jumps
  to a higher energy level
• Emission- an electron emits the absorbed energy
  and returns to a relaxed state

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Light Reactions

• Reactions that require light- Im sure you knew
  that already
• Takes place in the thylakoid membrane
• Divided into two systems Photosystem II and
  photosystem I
• Photosystem II comes first
• Electrons come from splitting of water molecules
  (2 water molecules for the whole reaction)
• Electrons will not start the reaction until hit
  by light that has been passed through chlorophyll
  molecules

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Light Reactions Continued

• Once hit by the light electrons move to an
  excited state then are transported by proteins to
  photosystem I- ATP is made in the process
• Electron arrives at the photosystem I and will
  stay there until light hits the electron again
• Electron moves to a higher energy level and will
  attach to NADP and convert it to NADPH (need 2
  electrons for this to happen) so the cycle needs
  to happen twice
• Final products are O2, NADPH,and ATP
• So when are the sugar molecules made?

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The Dark cycle (Calvin Cycle)

• The dark cycle is called that only because it
  does not require light- also called carbon
  fixation
• Enzymes use the ATP and NADPH from the light
  reactions to take carbon from CO2
• Reaction will not happen unless ATP and NADPH are
  present
• C from CO2 will combine with a 5-carbon starting
  material to make an unstable 6-carbon compound

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Calvin cycle continued

• Unstable 6-carbon molecule splits into 2 3-carbon
  molecules
• Energy from ATP is added to the 3-carbon
  molecules, and NADPH donates electrons to the
  3-carbon molecules
• 3-carbon molecules may combine to form glucose or
  lose a C atom and return to the beginning of the
  cycle as the 5-C starting material
• The lost C atoms will combine to form glucose
• 6 turns of the Calvin cycle1 glucose molecule

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Rates of Photosynthesis

• Rate of photosynthesis is dependent on the
  following factors light availability, carbon
  dioxide concentration, temperature
• How does the rate of photosynthesis change with
  those factors?
• Less light availableslower rate of
  photosynthesis
• Less carbon dioxide availableslower rate of
  photosynthesis
• Photosynthesis will occur at normal rates in a
  range of temperatures but will be slower if
  temperature is too high or low

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