Photosynthesis

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Photosynthesis

• Part 2

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Electron Carriers

• Electrons in chlorophyll absorb sunlight?the
  electrons gain a great deal of energy.
• Electron carriers transport high-energy electrons
  from chlorophyll to other molecules.

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Electron Carriers

• Analogy
• High-energy electronshot coals from a barbeque.
  Would you pick these coals up with your hands to
  transport them?
• NO
• We would use a pan or tongs to transport/carry
  the hot coals to another location
• Electrons are hot coals and NADP is the
  pan/tongs.
• Instead of a pan, electron carriers (NADP)
  transport high-energy electrons from chlorophyll
  to other molecules

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NADP (Electron Carrier)
NADP

• One carrier molecule is NADP.
• Electron carriers, such as NADP, transport
  electrons.
• NADP accepts and holds 2 high-energy electrons
  along with a hydrogen ion (H). This converts the
  NADP into NADPH.

NADP
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NADP (Electron Carrier)

• The conversion of NADP into NADPH is one way
  some of the energy of sunlight can be trapped in
  chemical form.
• The NADPH carries high-energy electrons to
  chemical reactions elsewhere in the cell.
• These high-energy electrons are used to help
  build a variety of molecules the cell needs,
  including carbohydrates like glucose

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2 Stages of Photosynthesis

• 1 Light-Dependent Reactions
• 2 Light-Independent Reactions AKA the Calvin
  Cycle

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Light-Dependent Reaction

• Takes place in the thylakoid membranes in the
  chloroplast

Chloroplast
Thylakoids
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Light-Dependent Reactions

• Requires sunlight
• Electrons are excited ? by sunlight

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Light-Dependent Reactions

• Water (H20) is split in half?H protons and
  oxygen gas
• Oxygen is released as a plants waste product
  however, animals use oxygen to respire (breathe)
• Hydrogen protons are carried by NADP to make
  NADPH and used in making sugar
• ATP (energy) and NADPH (electron carrier) are
  formed by the addition of energized electrons

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H2O
CO2
Light
NADP
ADP P
Light- dependent reactions
Calvin cycle
Sugars
O2
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Light-Dependent Review

• Water is broken down due to the energy of photons
  of sunlight which energize the electrons.
• The light-dependent reactions produce oxygen gas
  which leaves the chloroplast into the environment
• The light-dependent reactions convert ADP and
  NADP into the energy carriers ATP and NADPH
  using the excited electrons and the H protons.

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H2O
CO2
Light
NADP
ADP P
Light- dependent reactions
Calvin cycle
Sugars
O2